CN114729464A - Method for electrodepositing a pretreatment composition - Google Patents

Abstract

Methods for treating a substrate are disclosed. One method comprises the following steps: contacting the substrate with a pretreatment composition comprising a group IVB metal and an electropositive metal; and passing an electric current between the anode and the substrate acting as a cathode to deposit a coating on the substrate from the pretreatment composition. A method for treating an electrically conductive substrate further comprises contacting the electrically conductive substrate with a pretreatment composition comprising a group IVB metal and an electropositive metal; and electrodepositing a coating on the conductive substrate from the pretreatment composition. A method further includes contacting the electrically conductive substrate with a pretreatment composition comprising a group IVB metal and an electropositive metal; and electrodepositing a coating on the electrically conductive substrate from the pretreatment composition, wherein the coating comprises each of the group IVB metal and the electropositive metal.

Description

Method for electrodepositing a pretreatment composition

Technical Field

The present invention relates to the use of electrodeposition to provide coatings on metal substrates.

Background

It is common to use protective coatings on metal substrates to improve corrosion resistance and paint adhesion. Conventional techniques for coating such substrates include techniques involving pretreatment of the metal substrate with a chromium-containing composition. However, the use of such chromate-containing compositions can present environmental and health concerns.

Another common coating is a phosphate coating (e.g., zinc phosphate).

The application of zinc phosphate coatings (conversion coatings) typically requires surface conditioning of the metal prior to the phosphating step. An example of a surface conditioning step is rinsing in a colloidal suspension of a metal salt such as titanium phosphate or a dispersion of submicron to micron sized zinc phosphate particles. After surface conditioning, the metal substrate is exposed to zinc phosphate, for example by a bath process. While relatively effective in forming corrosion resistant coatings on metals (e.g., ferrous metals), zinc phosphating processes are often time consuming, require relatively high temperature processing, and present environmental concerns. Furthermore, there are limits to the level of aluminum that can be treated using zinc phosphate treatment, which represents a challenge in view of incorporating higher levels of aluminum in vehicle construction to improve weight savings. Thus, chromate-free and zinc phosphate-free pretreatment compositions have been developed. Such compositions are typically based on chemical mixtures that react with and bond with the substrate surface to form a protective layer. For example, pretreatment compositions based on group IVB metal compounds are becoming more prevalent. Such compositions typically comprise a source of free fluoride, i.e. fluoride available as a separate ion in the pretreatment composition, rather than fluoride combined with another element, such as a group IVB metal. The free fluoride can etch the surface of the metal substrate, thereby facilitating the deposition of a protective coating comprising a group IVB metal species. However, the corrosion resistance of these pretreatment compositions is often significantly poorer than conventional pretreatment containing chromium and zinc phosphate.

With respect to zirconium (group IVB metal) based pretreatment compositions, the coating weight of zirconium in the protective layer or film is a factor for obtaining adequate corrosion protection and paint adhesion. "coating weight" is the amount or mass of material in a given coating compared to a particular area. Coating weight may refer to the individual elements, individual compounds, or the sum of all elements and/or compounds that make up the coating. A representative minimum coating weight specification for a zirconium protective layer or film is 20 milligrams per square meter (mg/m)²) Based on zirconium. Various methods have been proposed to achieve acceptable zirconium coating weights. Increasing the concentration in the pretreatment coating bath will generally result in an increase in the weight of the zirconium coating, but at the expense of cost. To maintain reasonable costs, the pretreatment coating bath may limit the concentration of zirconium to a few hundred parts per million (ppm). The second method is to increase the deposition time. However, the process window and application time may be limited to from a few seconds to a few minutes, which may not allow enough time for the desired coating weight. A third method is to add an accelerator such as copper to the pretreatment coating bath. However, this approach can result in undesirable levels of promoters (e.g., copper) in the formed protective layer or film, which reduces corrosion resistance. Published techniques demonstrate controlled deposition of copper by use of chelating agents. In U.S. patent No. 9,580,813, the pre-treatment coating deposited on the metal substrate should have a ratio of the average total atomic percent of copper to the atomic percent of zirconium equal to or less than 1.1. The use of a chelating agent is generally undesirable because it may increase the difficulty and cost associated with wastewater treatment, as the chelating agent will prevent or otherwise treatThe precipitation of harmful metal ions (e.g., Ni, Cu, Cr) present in wastewater during wastewater treatment or recovery is suppressed. It would be desirable to provide a method for treating a metal substrate that overcomes at least some of the aforementioned drawbacks of the prior art, including the environmental disadvantages associated with the use of chromates and the limitations associated with the use of group IVB metals such as zirconium. It would also be desirable to provide a method for treating a metal substrate that imparts corrosion resistance equal to or even superior to that imparted by the use of a phosphate-containing conversion coating or a chromium-containing conversion coating. It is also desirable to provide related coated metal substrates.

Disclosure of Invention

The present invention relates to a method for treating a substrate, comprising: contacting the substrate with a pretreatment composition comprising a group IVB metal and an electropositive metal; and passing an electric current between the anode and the substrate acting as a cathode to deposit a coating on the substrate from the pretreatment composition.

The invention also relates to a method for treating an electrically conductive substrate comprising contacting the electrically conductive substrate with a pretreatment composition comprising a group IVB metal and an electropositive metal; and electrodepositing a coating on the conductive substrate from the pretreatment composition.

The invention further relates to a method for treating an electrically conductive substrate, comprising: contacting an electrically conductive substrate with a pretreatment composition comprising a group IVB metal and an electropositive metal; and electrodepositing a coating on the electrically conductive substrate from the pretreatment composition, wherein the coating comprises each of the group IVB metal and the electropositive metal.

Also disclosed are substrates treated according to the methods of the invention.

Drawings

FIG. 1 shows a schematic of an electrolytic cell and illustrates the passage of an electric current to facilitate deposition of a pretreatment layer or film on a substrate;

FIG. 2 shows a side view of a pretreatment apparatus comprising an anode and a substrate 220 connected by a DC power source and separated by a gasket through which a pretreatment composition is introduced according to example 2;

fig. 3 is a graph showing the effect of current density on zirconium deposition according to the method described in example 2. In the figure, Zr CW represents the zirconium coating weight;

figure 4 is a graph showing the effect of current density on zirconium/copper deposition according to the method described in example 2. In this figure, Zr CW/Cu CW represents the quotient of the zirconium coating weight and the copper coating weight, both expressed in milligrams per square meter; and is

Fig. 5 is a schematic view of the Spangler panel used in example 5.

Detailed Description

For the purposes of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, except in any operating examples, or where otherwise indicated, all numbers such as those expressing values, amounts, percentages, ranges, sub-ranges or fractions, may be read as if prefaced by the word "about", even if the term does not expressly appear. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. In the case of closed or open numerical ranges described herein, all numbers, values, amounts, percentages, subranges, and fractions within or encompassed by the numerical ranges are to be considered as specifically encompassed within the original disclosure of the present application and as if such numbers, values, amounts, percentages, subranges, and fractions were explicitly written out in their entirety.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

As used herein, unless otherwise specified, plural terms may encompass their singular counterparts and vice versa, unless otherwise specified. For example, although reference is made herein to "a" pretreatment composition and "an" electropositive metal, combinations of these components (i.e., a plurality of these components) may be used. In addition, in this application, the use of "or" means "and/or" unless specifically stated otherwise, even though "and/or" may be explicitly used in some cases.

As used herein, "comprising," "including," and similar terms, are understood in the context of this application to be synonymous with "including" and thus open-ended and do not exclude the presence of elements, materials, ingredients, and/or method steps that are not otherwise described or recited. As used herein, "consisting of … …" is understood in the context of the present application to exclude the presence of any non-specified elements, components and/or method steps. As used herein, "consisting essentially of … …" is understood in the context of this application to include the named elements, materials, ingredients, and/or method steps as well as elements, materials, ingredients, and/or method steps that do not materially affect the basic characteristics and novel characteristics of the described content.

As used herein, the terms "on … (on)", "on … (upon)", "onto …", "applied on …", "applied on …", "formed on …", "deposited on …", "deposited on …", "formed on …" mean formed, covered, deposited and/or provided on but not necessarily in contact with a surface. For example, a coating layer "formed on" a substrate does not preclude the presence of one or more other intermediate coating layers of the same or different composition located between the formed coating layer and the substrate.

As used herein, the term "group IVB metal" refers to an element in group IVB of the periodic table of elements of the Chemical abstracts Service ("CAS") version, as shown, for example, in Handbook of Chemistry and Physics (1983), 63 rd edition, which corresponds to group 4 in the actual IUPAC numbering.

As used herein, the term "group IVB metal compound" refers to a compound comprising at least one element in group IVB of the CAS version of the periodic table of the elements.

As used herein, the term "aluminum" when used in reference to a substrate refers to substrates made of or comprising aluminum and/or aluminum alloys, as well as coated aluminum substrates.

As used herein, the term "oxidizing agent," when used in reference to a component of a pretreatment composition, refers to a chemical capable of oxidizing a metal present in a substrate in contact with the pretreatment composition. As used herein with respect to "oxidizing agent," the phrase "capable of oxidizing" means capable of removing electrons from atoms or molecules (as the case may be) present in a substrate or pretreatment composition, thereby reducing the number of electrons of such atoms or molecules. Thus, the oxidizing agent is a chemical substance that is reduced in the above electrochemical reaction.

As used herein, unless otherwise disclosed herein, the term "total composition weight," "total weight of the composition," or similar terms, refers to the total weight of all ingredients present in the respective composition, including any carriers and solvents.

As used herein, unless otherwise disclosed herein, the term "substantially free" means that the particular material is not intentionally added to the composition and, if present, is present in the composition and/or layer comprising the composition in only trace amounts of one part per million (ppm) or less, based on the total weight of the composition or layer, as the case may be. As used herein, unless otherwise disclosed, the term "completely free" means that the particular material is present in the composition and/or layer comprising the composition in an amount of parts per billion (ppb) or less based on the total weight of the composition or layer, as the case may be.

As mentioned above, the present invention relates to a method for treating a substrate comprising, consisting essentially of, or consisting of: contacting the substrate with a pretreatment composition comprising, consisting essentially of, or consisting of a group IVB metal and an electropositive metal, wherein the group IVB metal is in a range of 4 times to 40 times the amount of the electropositive metal; and passing an electric current between the anode and a substrate that functions as a cathode to form a coating or film comprising, for example, a group IVB metal and an electropositive metal on the substrate from the pretreatment composition. The substrate may be used as a cathode in an electrodeposition process wherein both the cathode and a separate anode are immersed or partially immersed in the pretreatment composition.

The present invention relates to a method for treating a variety of substrates. The substrate may comprise a portion of a vehicle, such as a vehicle body (e.g., without limitation, a door, body panel, trunk lid, roof panel, hood, roof and/or rail, rivet, landing gear component, and/or skin used on an aircraft) and/or a vehicle frame. As used herein, "vehicle" or variations thereof include, but are not limited to, commercial, and military aircraft and/or land vehicles, such as automobiles, motorcycles, and/or trucks. Examples include, but are not limited to, substrates such as those often used to assemble vehicle bodies, vehicle parts, and other articles, such as small parts, including fasteners, e.g., nuts, bolts, pins, nails, clips, rivets, buttons, and the like. The substrate may be any conductive substrate. One type of conductive substrate is a metal substrate. Specific examples of metal substrates include, but are not limited to, single element substrates, metal alloy substrates, and/or metallized substrates, such as nickel plated plastic. According to the invention, the metal or metal alloy may comprise or may be steel, aluminium, zinc and/or magnesium. For example, the steel substrate may be Cold Rolled Steel (CRS), hot rolled steel, nickel flash steel, steel coated with zinc metal, zinc compounds or zinc alloys, such as electro galvanized steel, hot dip galvanized steel, galvanized steel and zinc alloy coated steel. In addition, aluminum alloys (e.g., alloys of 2XXX, 5XXX, 6XXX, or 7 XXX), aluminum-plated steels, and aluminum-alloyed steel substrates may also be used. Other suitable non-ferrous metals include copper and magnesium and alloys of these materials (e.g., magnesium alloys such as AZ31B, AZ91C, AM60B, ZEK100 or EV31A series). They may also comprise titanium and/or titanium alloys. The metal substrate treated with the pretreatment composition can be a cut edge of the substrate that is otherwise treated and/or coated on the remainder of its surface. The metal substrate may also be in the form of, for example, a metal sheet or a fabricated part.

Conductive substrates also suitable for treatment according to the method of the present invention include conductive polymers and conductive polymer composites, such as Carbon Fiber Reinforced Plastics (CFRP).

The substrate to be treated according to the disclosed method may first be cleaned to remove grease, dirt, and/or other foreign substances. At least a portion of the substrate surface may be cleaned by physical and/or chemical means, such as mechanically abrading the surface and/or cleaning/degreasing the surface with commercially available alkaline or acidic cleaners well known to those skilled in the art. Examples of alkaline cleaners suitable for use in the present invention include, but are not limited to, Chemkleen (TM) (CK)163, 177, 611L, 490MX, 2010LP, SP1, each of which is commercially available from PPG Industries, Inc., and Turco 4215NC-LT and Ridoline 298, each of which is commercially available from Henkel AG & Co.

After cleaning the substrate or the substrate surface, the substrate may be rinsed with an aqueous solution of tap water, deionized water, and/or a rinsing agent to remove any residue. The wet substrate surface may optionally be deoxidized (e.g., aluminum substrate) or de-rusted (e.g., iron substrate). Instead of or prior to deoxidizing/descaling the substrate surface, the substrate may be dried, such as, for example, by air drying using an air knife, by flashing off water by briefly exposing the substrate to elevated temperatures, or by passing the substrate between squeegee rollers.

At least a portion of the cleaned substrate surface may be mechanically and/or chemically deoxygenated. As used herein, the term "deoxygenation" refers to the removal of an oxide layer found on the surface of a substrate in order to promote uniform deposition of a pretreatment composition (as described below), as well as to promote adhesion of a pretreatment composition coating to the substrate surface. Suitable oxygen scavengers are familiar to the person skilled in the art. Typical mechanical deoxidizers can be uniformly roughened substrate surfaces, such as by use of a scrubbing or cleaning pad. Typical chemical deoxidizers include, for example, acid-based deoxidizers such as phosphoric acid, nitric acid, fluoroboric acid, sulfuric acid, chromic acid, hydrofluoric acid, and ammonium bifluoride, or the Amchem 7/17 deoxidizer (available from Henkel Technologies, Madison Heights, MI), the OAKITE deoxidizer LNC (available from Chemetall), the TURCO deoxidizer 6 (available from hangao), or combinations thereof. Typically, the chemical oxygen scavenger comprises a carrier, typically an aqueous medium, such that the oxygen scavenger may be in the form of a solution or dispersion in the carrier, in which case the solution or dispersion may be contacted with the substrate by any of a variety of known techniques, such as dipping or immersion, spraying, intermittent spraying, spraying after dipping, dipping after spraying, brushing, or rolling. When applying the solution or dispersion to a metal substrate, the skilled artisan will select the temperature range of the solution or dispersion based on the etch rate, for example, in a temperature range of 50 ° f to 150 ° f (10 ℃ to 66 ℃), such as 70 ° f to 130 ° f (21 ℃ to 54 ℃), such as 80 ° f to 120 ° f (27 ℃ to 49 ℃). The contact time may be 5 seconds to 10 minutes, such as 15 seconds to 5 minutes, and such as 30 seconds to 3 minutes. Rust removal typically involves removing weld rust, light oxides, and other impurities from ferrous surfaces. A representative rust removal product is CORROSOL 888 (available from PPG Industrial Coatings). The substrate may be immersed in a bath of a rust removing product (e.g., CORROSOL 888) at an elevated temperature, such as 95 to 160F (35 to 71℃), such as 100 to 150F (38 to 66℃), such as 105 to 145F (41 to 63℃), such as 110 to 140F (43 to 60℃), for 5 seconds to 3 minutes.

After any optional deoxidation/descaling, the substrate may optionally be rinsed with tap water, deionized water, or an aqueous solution of a rinsing agent, and may optionally be dried as described above.

The cleaned and optionally deoxidized/descaled substrate may be contacted with a pretreatment composition in the form of an aqueous solution comprising, consisting essentially of, or consisting of a group IVB metal and an electropositive metal. The method or process of forming a coating or film on a substrate from the pretreatment composition is aided by the application of an electric current. In the method or process, the anode and the conductive substrate being treated (serving as the cathode) are placed in an aqueous solution or bath of the pretreatment composition. When an external bias is applied, i.e., a current is applied between the cathode and the anode while the cathode and the anode are in contact with the pretreatment composition, a layer or film will be formed on the surface of the substrate from the pretreatment composition. The presence of an electric current to assist or assist in depositing a layer or film on a substrate may characterize the method or process as electrodeposition. One method may be characterized by depositing a group IVB metal at the cathode with a current assisted pretreatment ("CAPT").

Electrodeposition (electrodeposition) may include immersing an electrically conductive substrate, which serves as a cathode in an electrical circuit including a cathode and an anode (e.g., an inert metal such as platinum or a passivating metal such as stainless steel), in a bath of an aqueous pretreatment composition. Sufficient current is applied between the electrodes to aid or assist in depositing a layer or film comprising the constituents of the pretreatment composition on or over at least a portion of the surface of the conductive substrate (e.g., to aid or assist in the deposition rate and/or amount of group IVB metal deposited). Such deposition includes, for example, covering at least 75% of the surface of the substrate immersed in the pretreatment composition, such as at least 85% of the surface of the substrate, such as at least 95% of the surface of the substrate. Further, it should be understood that, as used herein, a pretreatment layer or film or coating formed "on" at least a portion of a "substrate" refers to a composition formed directly on at least a portion of the surface of the substrate, including the entire portion, as well as a composition or coating formed on any coating or pretreatment material previously applied to at least a portion of the substrate.

Electrodeposition can be carried out at an absolute value of-0.1 milliamperes per square centimeter (mA/cm) of substrate²) To substrate | -20| mA/cm²At a current density of, for example, | -0.1| mA/cm of the substrate²To substrate | -12| mA/cm²For example, | -0.3| mA/cm of the substrate²To substrate | -2.5| mA/cm²E.g. of the substrate|-0.35|mA/cm²To substrate | -1| mA/cm²E.g., | -1| mA/cm less than that of the substrate²For example, | -0.1| mA/cm of the substrate²To substrate | -1| mA/cm²For example, | -0.4| mA/cm of the substrate²To substrate | -0.8| mA/cm²For example, | -0.5| mA/cm of the substrate²To substrate | -0.7| mA/cm²E.g. | -0.6| mA/cm less than that of the substrate²And e.g. | -0.1| mA/cm of the substrate²To substrate | -0.6| mA/cm². As used herein, "absolute value" is represented by "| X |", where X is a positive or negative number, and | + X | is equal to | -X |. In the case of current density, the negative sign represents the cathodic current density and the positive sign represents the anodic current density. For example, | -12| mA/cm²Current density of-12 mA/cm²The cathode current density of (a). Those skilled in the art of electrodeposition will appreciate the amperage and voltage requirements needed to achieve the disclosed current density ranges. The current may be applied at a constant applied external voltage (e.g., direct current).

The use of an electric current, for example, contributes to the deposition rate and/or amount of group IVB metal deposited on the substrate, particularly in the region of the substrate that is within the electric field generated by applying the electric current between the electrodes. The acidic nature of the pretreatment composition itself will also promote deposition (passive deposition) on the metal substrate in the absence of an electric current or in areas of the substrate that are not in direct contact with an electric field (i.e., the current may be negligible or zero). The process allows for the electrically-assisted and passive deposition of group IVB metals on a substrate.

As described above, the pretreatment composition can include a group IVB metal and an electropositive metal. For example, the group IVB metal can be titanium, zirconium, hafnium, or a combination thereof. The group IVB metal may be incorporated into the pretreatment composition as a compound such as an inorganic or organic salt. Suitable zirconium compounds include, but are not limited to: hexafluorozirconic acid, alkali metal and ammonium salts of hexafluorozirconic acid, ammonium zirconium carbonate, zirconyl nitrate, zirconyl sulfate, zirconium carboxylates, and zirconium hydroxy carboxylates such as zirconium acetate, zirconium oxalate, ammonium zirconium glycolate, ammonium zirconium lactate, ammonium zirconium citrate, and mixtures thereof. Suitable compounds of hafnium include, but are not limited to, hafnium nitrate.

As will be understood by those skilled in the art, the tendency of a chemical to be reduced is referred to as the reduction potential, expressed in volts, and is measured relative to a standard hydrogen electrode, arbitrarily designated as a zero reduction potential. The reduction potentials of several elements are listed in Table 1A below (according to CRC 82 th edition, 2001-. If the voltage value E of one element or ion is more positive (in the table below) than the element or ion to which it is compared, said element or ion is more easily reduced than the other element or ion.

TABLE 1A

Element(s)	Reduction of half cell reactions	Voltage, E
			Potassium salt	K++e→K	-2.93
Calcium carbonate	Ca2++2e→Ca	-2.87
			Sodium salt	Na++e→Na	-2.71
Magnesium alloy	Mg2++2e→Mg	-2.37
			Aluminium	Al3++3e→Al	-1.66
Zinc	Zn2++2e→Zn	-0.76
			Chromium (III)	Cr3++3e→Cr	-0.74
Iron	Fe2++2e→Fe	-0.45
			Nickel (II)	Ni2++2e→Ni	-0.26
Tin (Sn)	Sn2++2e→Sn	-0.14
			Lead (II)	Pb2++2e→Pb	-0.13
Hydrogen	2H++2e→H2	-0.00
			Copper (Cu)	Cu2++2e→Cu	0.34
Mercury	Hg2 2++2e→2Hg	0.80
			Silver (Ag)	Ag++e→Ag	0.80
Gold (Au)	Au3++3e→Au	1.50

Thus, as will be apparent, when the electrically conductive substrate is a metal substrate comprising one of the materials listed previously, such as cold rolled steel, hot rolled steel, steel coated with a zinc metal, zinc compound or zinc alloy, hot dip galvanized steel, steel plated with a zinc alloy, aluminum plated steel, aluminum alloy plated steel, magnesium and magnesium alloy, suitable electropositive metals for deposition thereon include, for example, nickel, copper, silver and gold, and mixtures thereof. Considering the positive values of the overall electrochemical reaction, these metals will spontaneously deposit on e.g. steel or aluminium alloys, as shown in table 1B. The term "electropositive metal" refers to a metal ion that will be reduced by the metal substrate being treated when the pretreatment solution contacts the surface of the metal substrate.

TABLE 1B spontaneous deposition of electropositive metals on Steel substrates

Metal ion	Reduction of half cell reactions	Half cell potential (V)	E with a steel substrateBattery with a battery cell(1)
				Ni2+	Ni2++2e→Ni	-0.26V	0.19V
Cu2+	Cu2++2e→Cu	0.34V	0.79V
				Ag+	Ag++e→Ag	0.80V	1.25V
Au3+	Au3++3e→Au	1.50V	1.95V

(1) Calculation of E using the conversion of iron (0) to iron (II) as the oxidation half-cell reaction_{Battery with a battery cell}The value was + 0.45V. This is an alternative to oxidation of the steel substrate.

When the electropositive metal is or includes copper, both soluble and insoluble compounds may be used as a source of copper in the pretreatment composition. For example, the source of the copper ions in the pretreatment composition can be a water-soluble copper compound. Specific examples of such compounds include, but are not limited to, copper sulfate, copper nitrate, copper pyrophosphate, copper thiocyanate, copper bromide, copper oxide, copper hydroxide, copper chloride, copper fluoride, copper fluorosilicate, copper fluoroborate, and copper iodate, as well as copper salts of carboxylic acids in the homologous series of formic acid and capric acid.

The group IVB metal may be present in the pretreatment composition in an amount in the range of 4 to 40 times by weight the amount of the electropositive metal, 5 to 40 times by weight the amount of the electropositive metal, or 5.7 to 40 times by weight the amount of the electropositive metal. The group IVB metal, calculated as the elemental metal, can be present in the pretreatment composition in an amount of 100 parts per million (ppm) or more, such as 200ppm, 250ppm, 300ppm, 350ppm, based on the total weight of the ingredients in the pretreatment composition. The amount of group IVB metal in the pretreatment composition can range between and including the recited values.

The electropositive metal may be present in the pretreatment composition in an amount by weight in the range of 4 to 40 times less than the amount by weight of the group IV metal. Examples of amounts of electropositive metal, calculated as elemental metal, when the group IVB metal is present in the pretreatment composition in an amount of 200ppm by weight are 5ppm (40.0 times lower), 20ppm (10.0 times lower), 30ppm (6.7 times lower), 35ppm (5.7 times lower), 40ppm (5.0 times lower), and 50ppm (4.0 times lower). The amount of electropositive metal in the pretreatment composition can range between and including the recited values.

According to the present invention, a fluoride source may be present in the pretreatment composition. As used herein, the amount of fluoride disclosed or reported in the pretreatment composition is referred to as "free fluoride," i.e., fluoride that is present in the pretreatment composition without binding of metal ions or hydrogen ions, as parts of fluoride in parts per million. Free fluoride is defined herein as being able to use, for example, an Orion Dual Star two-channel bench-top meter (available from Thermo Fisher Scientific) equipped with a fluoride ion selective electrode ("ISE"), symp supplied by VWR International

Fluoride ion is measured selectively in combination with an electrode or the like.See, for example, Light and Cappuccino, "Determination of fluoride in toothpaste using ion-selective electrodes (Determination of fluoride in toothpaste using an-selective electrode)", journal of chemical education (J.chem.Educ.), 52:4, 247-. Fluoride ISE can be normalized by immersing the electrode in a solution of known fluoride concentration and recording readings in millivolts, and then plotting these millivolt readings in a log plot. The millivolt reading of the unknown sample can then be compared to the calibration map and the concentration of fluoride determined. Alternatively, the fluoride ISE may be used with a meter that will perform calibration calculations internally, so after calibration, the concentration of the unknown sample can be read directly.

Fluoride is a small negative ion with a high charge density, so in aqueous solution it is often complexed with metal ions or hydrogen ions with a high positive charge density. Fluoride anions in solution that are bound to metal cations or hydrogen ions or covalently are defined herein as "bound fluoride". Such complexed fluoride ions cannot be measured with fluoride ISE unless the solution in which they are present is mixed with an ionic strength adjusting buffer (e.g. citrate anion or EDTA) that releases fluoride ions from such complexes. At this point (all) fluoride ions can be measured by the fluoride ISE and the measurement is referred to as "total fluoride". The sum of the concentrations of bound fluoride and free fluoride equals the total fluoride, which can be determined as described herein.

The total fluoride in the pretreatment composition can be provided by hydrofluoric acid as well as alkali metal and ammonium fluoride or hydrogen fluoride. Additionally, the total fluoride in the pretreatment composition can be derived from group IVB metals present in the pretreatment composition including, for example, hexafluorozirconic acid or hexafluorotitanic acid. Other complex fluorides, e.g. fluosilicic acid (H)₂SiF₆) Or fluoroboric acid (HBF)₄) May be added to the pretreatment composition to provide total fluoride. Those skilled in the art will appreciate that the presence of free fluoride in the pretreatment bath may affect the pretreatment deposition and etching of the substrate, and therefore measuring this bath parameter is critical. The level of free fluoride willDepending on the pH and addition of the chelating agent to the pretreatment bath and indicating the extent to which fluoride associates with the metal ions/protons present in the pretreatment bath. For example, pretreatment compositions of the same total fluoride level may have different levels of free fluoride, which will be affected by the pH and chelating agents present in the pretreatment solution. Thus, two different pretreatment compositions having the same total fluoride may have different pretreatment deposition properties and thus different corrosion properties.

According to the present invention, the free fluoride of the pretreatment composition can be present in an amount of at least 15ppm to no more than 2500ppm, such as 25ppm to no more than 1000ppm, such as 50ppm to no more than 250ppm, wherein all concentrations are based on the total weight of the pretreatment composition. The amount of free fluoride in the pretreatment composition can range between and including the recited values. As the group IVB metal is deposited on the substrate during the pretreatment process, the pretreatment composition will experience consumption of the group IVB metal (e.g., zirconium) and the fluorine in the hexafluorozirconic acid will become free fluoride, for example, and if not controlled, the level of free fluoride in the pretreatment composition will increase with time as the substrate is pretreated with the pretreatment composition. Thus, pK can be formed_spThe metal, which is a fluoride salt of at least 11, is added to the bath containing the pretreatment composition as disclosed in U.S. patent No. 8,673,091, column 6, line 11 to column 7, line 20, which is incorporated herein by reference. pK_spRefers to the logarithmic inverse of the solubility product constant of the compound. For the purposes of the present invention, the pK of the metal fluoride salt_spValues refer to pK reported in Lange's Handbook of Chemistry, 15 th edition, McGraw-Hill, 1999, Table 8.6_spThe value is obtained. In certain embodiments of the invention, a pK is formed_spThe metal of the fluoride salt being at least 11 is selected from cerium (CeF)₃pK of (2)_sp15.1) lanthanum (LaF)₃pK of (2)_sp16.2), scandium (ScF)₃pK of (2)_sp23.24), Yttrium (YF)₃pK of (2)_sp20.06) or mixtures thereof. Alternatively or additionally, depleted group IVB metalsThe pretreatment composition (e.g., bath) can be supplemented with a fluoride-reduced group IVB composition (the amount of group IVB metal in the pretreatment composition can be supplemented). In the case of zirconium, these fluoride deficient IVB compositions can be prepared by mixing hexafluorozirconic acid with zirconium basic carbonate or zirconyl nitrate in different ratios. By adding these fluoride-deficient compositions to the bath, the level of free fluoride present in the bath to be depleted in group IVB will be controlled.

The pH of the pretreatment composition may be in the range of 3.0 to 7.0, such as 3.5 to 6.8, such as 4 to 6, such as 4 to 5.5, such as 4 to 5, such as 4.2 to 6.5, such as 4.5 to 5.5, such as 4.5 to 6.0, such as 4.7 to 5.5, and may be adjusted as desired using, for example, any acid and/or base. The pH of the composition may be maintained by including an acidic material comprising a water-soluble and/or water-dispersible acid, such as hexafluorozirconic acid, nitric acid, sulfuric acid, and/or phosphoric acid. The pH of the composition can be maintained by including a basic material comprising a water-soluble and/or water-dispersible base, such as an alkali metal hydroxide (e.g., sodium hydroxide, potassium hydroxide), an alkali metal carbonate (e.g., sodium carbonate, potassium carbonate), ammonium hydroxide, ammonia, and/or an amine, such as triethylamine, methylethylamine, or mixtures thereof.

Figure 1 shows a schematic representation of an electrolytic cell and illustrates that the passage of electric current facilitates the deposition of a pretreatment layer or film on a substrate. The cell 100 includes a volume of pretreatment composition 110 in the form of an aqueous solution. The pretreatment composition in the form of an aqueous solution may be at a temperature in the range of 60 ° f to 200 ° f (15 ℃ to 93 ℃), such as 60 ° f to 150 ° f (15 ℃ to 65 ℃), such as 60 ° f to 125 ° f (15 ℃ to 52 ℃), such as 60 ° f to 100 ° f (15 ℃ to 38 ℃), such as 60 ° f to 90 ° f (15 ℃ to 32 ℃), such as 70 ° f to 180 ° f (21 ℃ to 82 ℃), such as 70 ° f to 150 ° f (21 ℃ to 66 ℃), such as 70 ° f to 125 ° f (21 ℃ to 52 ℃), such as 70 ° f to 100 ° f (21 ℃ to 38 ℃), such as 70 ° f to 90 ° f (21 ℃ to 32 ℃), such as 77 ° f to 150 ° f (25 ℃ to 66 ℃), such as 77 ° f to 100 ° f (25 ℃ to 38 ℃) and such as 77 ° f to 90 ° f (25 ℃ to 32 ℃).

Is arranged in a pretreatment combinationWithin object 110 is an anode 120 of an inert metal such as platinum or a passivating metal such as stainless steel and a substrate 130 that serves as a cathode and upon which a pretreatment layer or film is deposited or formed. A dc power supply 140 is connected between the anode 120 and the substrate 130. A constant voltage (potential difference) is applied between the anode 120 and the substrate 130 to drive the decomposition of water in the aqueous solution into oxygen (at the anode) and hydrogen (at the cathode). Standard potential difference of water electrolytic cell (E)_{Battery with a battery cell}＝E_{Cathode electrode}–E_Anode) At 25 ℃ at pH 0, at-1.23 volts (standard concentration of H + 1M). Without wishing to be bound by theory, it is believed that electrolysis of water to oxygen and hydrogen generates hydroxyl groups (OH) at the interface of the substrate 130 and the pretreatment composition^-). The resulting hydroxide groups interact with the group IVB metal ions (e.g., ZrF) in the pretreatment composition₆ ^2-) React and form an oxide film or layer (e.g., zirconia) on the substrate 130. Increasing the amount of hydroxide ions at the interface will tend to increase the rate of formation of a group IVB metal oxide film or layer (e.g., increase the rate of fluoride and oxide/hydroxide metathesis leading to zirconium precipitation). Suitable voltages for forming the pretreatment film or layer on the substrate 130 are from 0.10 volts to 100 volts, such as from 0.50 volts to 50.00 volts, such as from 0.75 volts to 35.00 volts, such as from 1.00 volts to 20.00 volts. The current density at the substrate 130 may be between | -20| milliamperes per square centimeter (mA/cm)²) In a range of, for example, | -0.1| mA/cm²To | -10| mA/cm²、|-0.1|mA/cm²To 1| mA/cm²And | -0.1| mA/cm²To | -0.6| mA/cm². The current density can be expressed as a positive or negative value depending on the direction of electron flow. As mentioned above, the negative sign of the current density refers to cathodic deposition.

The thickness of the pretreatment film, layer, or coating formed from the pretreatment composition on a substrate (e.g., substrate 130 in fig. 1) can be less than 1 micron, e.g., 10 nanometers to 600 nanometers, e.g., 20nm to 400nm, e.g., 250nm to 300nm, e.g., 30nm to 250 nm. The coating weight of the group IVB metal (e.g. zirconium) in the pretreatment layer, coating or film may be 20mg/m²Or greater, e.g. 20mg/m²To 250mg/m²E.g. 25mg/m²To 200mg/m²For example 30mg/m²To 250mg/m²For example 30mg/m²To 200mg/m²E.g. 40mg/m²To 250mg/m²E.g. 40mg/m²To 200mg/m²For example 50mg/m²To 250mg/m²For example 50mg/m²To 200mg/m²E.g. 75mg/m²To 250mg/m²For example 75mg/m²To 200mg/m²E.g. 100mg/m²To 250mg/m²E.g. 100mg/m²To 200mg/m²E.g. 150mg/m²To 250mg/m²E.g. 150mg/m²To 200mg/m²For example 50mg/m²To 150mg/m²And for example 75mg/m²To 150mg/m². The weight ratio of the group IVB metal to the electropositive metal in the pretreatment layer, coating or film on the substrate (e.g., metal substrate) can be greater than 2:1, e.g., 2.5:1, 3.0:1, 3.5:1, 4:1, 4.5:1, 4.7:1, 5:1, 6:1, 10:1, 15:1, and 20: 1. The coating weight of the group IVB metal on the substrate and the weight ratio of the group IVB metal to the electropositive metal in the pretreatment layer will depend in part on the immersion time in the pretreatment bath and the current density applied to the bath.

The rate of group IVB metal deposition is an important factor in ensuring proper corrosion protection, provided that many industrial processes are limited to seconds to minutes. As described above, application of a cathodic bias will increase the rate of deposition of the group IVB metal (e.g., zirconium). In this specification, deposition rate is defined as the deposition over a given substrate area (1 m)²) The mass of zirconium (Zr) above, in mg, is normalized within one second. In the present invention, the rate of metal deposition may be at least 0.2mg Zr/sec to 2.0mg Zr/sec, such as 0.2mg Zr/sec to 1.8mg Zr/sec, such as 0.4mg Zr/sec to 1.6mg Zr/sec, such as 0.6mg Zr/sec to 1.5mg Zr/sec, such as 0.75mg Zr/sec to 1.4mg Zr/sec, such as 0.9mg Zr/sec to 1.25mg Zr/sec.

After depositing a pretreatment layer, coating or film on a substrate from the pretreatment composition in an electrodeposition pretreatment operation, the substrate may be rinsed with an aqueous solution of tap water, deionized water and/or a rinsing agent to remove any residue. Alternatively, the substrate may be dried.

The substrate having the pretreatment coating, film or layer thereon (pretreated substrate) can optionally be further processed to include one or more other coatings, films or layers. One such optional coating, film or layer is a paint. Typically, the pretreated substrate may be painted using an electrocoating process, wherein the pretreated substrate is placed in a bath containing deionized water and paint solids. The electrodes placed in the bath are charged the same as the paint solids. When a charge is applied to the bath, paint solids are driven off the electrodes and deposited on the pretreated substrate. Following the electrodeposition process, the painted pretreated substrate may be rinsed and then baked at elevated temperatures (e.g., 160 ° f (82 ℃) to 400 ° f (204 ℃)) to crosslink and cure the paint on the substrate. On ferrous substrates (e.g., cold rolled steel), rust corrosion creep is commonly observed at the scratch and cut edges in accelerated and outdoor exposure corrosion tests. After removal from the corrosive environment, filiform corrosion may begin at the site of the corrosive corrosion, leading to further surface corrosion failure. Historically, this behavior has been observed even though the substrate has been subjected to conventional zinc phosphate or next generation film pretreatments. Current-assisted pretreatment of pretreatment compositions comprising a group IVB metal and an electropositive metal have shown the ability to inhibit or resist filiform corrosion of a substrate (e.g., an iron or aluminum substrate). A pretreatment that inhibits filiform corrosion may be highly desirable-particularly in the automotive OEM industry-because it may prevent further surface corrosion failure after damage to the coating covering the pretreated substrate (e.g., chip damage on a vehicle). Furthermore, this property of the pre-treatment film may facilitate repair of damaged coatings by inhibiting the diffusion of corrosion from the initial site of coating failure. In addition, current-assisted thin film pretreatment of pretreatment compositions comprising a group IVB metal and an electropositive metal can extend the service life of automotive or industrial coatings.

In accordance with the present invention, the pretreatment film or layer deposited on the substrate may be substantially free of phosphate, phosphate ions, or phosphate-containing compounds, or in some cases may be completely free of phosphate, phosphate ions, or phosphate-containing compounds. In some cases, the pretreatment composition may not include phosphate ions or phosphate-containing compounds and/or the formation of sludge that forms with zinc phosphate-based treatments, such as aluminum phosphate, iron phosphate, and/or zinc phosphate. As used herein, "phosphate-containing compound" includes compounds containing elemental phosphorus, such as orthophosphates, pyrophosphates, metaphosphates, tripolyphosphates, organophosphonates, and the like, and may include, but is not limited to, monovalent, divalent, or trivalent cations such as: sodium, potassium, calcium, zinc, nickel, manganese, aluminum and/or iron. When the composition and/or coating, layer or film comprising the composition is substantially free, substantially free or completely free of phosphate, this includes phosphate ions or compounds containing phosphate in any form.

Thus, the pretreatment composition and/or the coating, layer, or film, respectively, deposited from the pretreatment composition can be substantially free, and/or can be completely free of one or more of any of the elements or compounds listed in the preceding paragraph. By a pretreatment composition and/or a coating, layer or film deposited from the pretreatment composition being substantially free of phosphate, it is meant that phosphate ions or phosphate-containing compounds are not intentionally added, but may be present in trace amounts, such as due to impurities or unavoidable contamination from the environment. In other words, the amount of material is so small that it does not affect the properties of the composition; this may further include that phosphate is not present in the pretreatment composition and/or in the coating, layer or film deposited from the pretreatment composition at levels at which they pose a burden on the environment. The term "substantially free" means that the pretreatment composition and/or a coating, layer, or film deposited from the pretreatment composition contains less than ten parts per million (ppm) of any or all of the phosphate anions or compounds listed in the preceding paragraph, if any, based on the total weight of the composition or layer or film, respectively. The term "substantially free" means that the pretreatment composition and/or a coating, layer, or film comprising the pretreatment composition contains less than 1ppm of any or all of the phosphate anions or compounds listed in the preceding paragraph. The term "completely free" means that the pretreatment composition and/or a coating, layer, or film comprising the pretreatment composition contains less than one part per billion (ppb) of any or all of the phosphate anions or compounds listed in the preceding paragraph, if any.

According to the present invention, the pretreatment film or layer deposited on the substrate may not include chromium or chromium-containing compounds. As used herein, the term "chromium-containing compound" refers to a material comprising hexavalent chromium. Non-limiting examples of such materials include chromic acid, chromium trioxide, chromic anhydride, dichromates, such as ammonium dichromate, sodium dichromate, potassium dichromate, and calcium dichromate, barium dichromate, magnesium dichromate, zinc dichromate, cadmium dichromate, and strontium dichromate. When the pretreatment composition and/or the coating or layer, respectively, deposited from the pretreatment composition is substantially free, or completely free of chromium, this includes any form of chromium, such as, but not limited to, the hexavalent chromium-containing compounds listed above.

Thus, the pretreatment composition and/or the coating, layer, or film, respectively, deposited from the pretreatment composition can be substantially free, and/or can be completely free of one or more of any of the elements or compounds listed in the preceding paragraph. The pretreatment composition and/or the coating, layer or film, respectively, deposited from the pretreatment composition, are substantially free of chromium or derivatives thereof, meaning that chromium or derivatives thereof are not intentionally added, but may be present in trace amounts, for example, due to impurities or unavoidable contamination from the environment. In other words, the amount of material is so small that it does not affect the performance of the pretreatment composition; in the case of chromium, this may further include that the element or compound thereof is not present in the pretreatment composition and/or in the coating, layer or film, respectively, deposited from the pretreatment composition at a level at which it places a burden on the environment. The term "substantially free" means that the pretreatment composition and/or the coating, layer, or film, respectively, deposited from the pretreatment composition contains less than 1ppm, based on the total weight of the composition or coating, layer, or film, respectively, of any or all of the elements or compounds listed in the preceding paragraph, if any. The term "substantially free" means that the pretreatment composition and/or a coating, layer, or film, respectively, deposited from the pretreatment composition contains less than 0.1ppm of any or all of the elements or compounds listed in the preceding paragraph, if any. The term "completely free" means that the pretreatment composition and/or a coating, layer, or film, respectively, deposited from the pretreatment composition contains less than one part per billion (ppb) of any or all of the elements or compounds listed in the preceding paragraph, if any.

It will be appreciated by those skilled in the art that changes could be made to the aspects described above without departing from the broad inventive concept thereof. It is understood, therefore, that this disclosure is not limited to the particular aspects disclosed, but it is intended to cover modifications within the spirit and scope of the disclosed methods, as defined by the appended claims.

Examples of the invention

Example 1 comparison of corrosion resistance at the same coating weight for Zr

Preparation of zirconium pretreatment composition:a zirconium-containing pretreatment composition or bath was prepared for testing. Each pretreatment bath was prepared by adding a metal-containing substance (e.g., hexafluorozirconic acid or potassium hexafluorozirconate for zirconium (Zr), copper nitrate for copper (Cu), or potassium chromium (III) sulfate for chromium (Cr)), and described in more detail with each example (copper and trivalent chromium represent electropositive metals with respect to the substrate (e.g., cold rolled steel (iron) or aluminum)). Zirconium was supplied to the copper-containing pretreatment bath by the addition of hexafluorozirconic acid (a 45 wt.% aqueous solution) available from Honeywell International, Inc (Honeywell International, Inc.) (Morristown, NJ); copper was provided by adding a 2 wt.% Cu solution prepared by diluting a copper nitrate solution (18 wt.% Cu in water) available from Shepherd Chemical Company (Cincinnati, OH). Zirconium was supplied to the chromium-containing pretreatment bath by adding potassium hexafluorozirconate (solid) available from Sigma Aldrich (Sigma Aldrich) (Milwaukee, WI); chromium is produced by the addition of potassium chromium (III) sulfate dodecahydrate available from sigma aldrich (milwaukee, wi) (solid,purity is more than or equal to 98 percent). After all ingredients were added to the pretreatment bath, the bath pH was measured using a pH meter interface (DualStar pH/ISE dual channel bench scale available from selmefeishil technologies, Waltham, Massachusetts, USA; pH probe, Fisher Scientific account pH probe (Ag/AgCl reference electrode)) immersed in the pretreatment bath. Free fluoride was measured using a DualStar pH/ISE two channel bench top meter (seimer feishel technologies) equipped with a fluoride selective electrode (Orion ISE fluoride electrode, solid state, available from seimer feishel technologies) by immersing the electrode in the pretreatment solution and allowing the equilibrium to be measured. The pH was then adjusted to the specified pH range using Chemfil buffer (an alkaline buffer solution, commercially available from PPG industries) as needed for increasing the pH. To lower the pH, hexafluorozirconic acid (a 45 wt.% aqueous solution available from honeywell international corporation, moleston, nj) was used in the copper-containing pretreatment bath. To reduce the pH of the chromium-containing pretreatment bath, a sulfuric acid solution (about a 10 wt.% aqueous solution, prepared from 93-98% sulfuric acid, available from Alfa Aesar, Tewksbury, MA) was used. Free fluoride was adjusted to a range of 25ppm to 150ppm using Chemfos AFL (a partially neutralized aqueous ammonium bifluoride solution, commercially available from PPG industries, and used according to supplier's instructions) as needed. The amount of Copper in each pretreatment bath was measured using a DR/890 colorimeter (available from HACH, raveland, Colorado, USA) using an indicator (CuVer1 Copper Reagent Powder pad (CuVer1 Copper Reagent Powder balls, available from HACH). The amount of Zr in the copper-containing pretreatment bath is calculated from the amount of hexafluorozirconic acid added and is reported based on the total weight of the composition. The amount of Cr in the chromium-containing pretreatment bath was calculated from the amount of added potassium chromium (III) sulfate dodecahydrate and reported based on the total weight of the composition. The amount of Zr in the chromium-containing pretreatment bath is calculated from the amount of potassium hexafluorozirconate added and is reported based on the total weight of the composition.

Preparation of PT bath A (PT A):by adding 18.9 liters of deionization to an empty 5 gallon plastic bucketWater (DI) to prepare PT bath a. Hexafluorozirconic acid and copper nitrate solution were added to DI water. The bath pH and free fluoride were adjusted by using Chemfil buffer and Chemfos AFL, respectively. PT bath a was applied at a "low" setting using an immersion heater.

Preparation of PT bath B (PT B):PT bath B was prepared in a similar manner to PT bath a by adding 18.9 liters of water to an empty 5 gallon plastic bucket. Hexafluorozirconic acid and copper solution were added to DI water, with the final amount (concentration) of copper in the pretreatment bath being lower than the final amount (concentration) of copper in PT bath a. The pH of the bath and free fluoride were adjusted using Chemfil buffer and Chemfos AFL, respectively. PT bath B was applied using an immersion heater at a "low" setting.

Preparation of PT bath C (PT C):PT bath C was prepared in a similar manner to PT bath a by adding 18.9 liters of water to an empty 5 gallon plastic bucket. Hexafluorozirconic acid and copper solution were added to DI water. The bath pH and free fluoride were adjusted by using Chemfil buffer and Chemfos AFL, respectively. The bath was divided into five 1 gallon aliquots. For conditions 1C, 1D, 1E, and 1F, a single 1 gallon aliquot was used. The last aliquot was discarded. To prepare the panels, a single 1 gallon aliquot was placed into a plastic cylinder with a magnetic stir bar. Stir 1 gallon bath at 300RPM on a magnetic stir plate.

Preparation of PT bath D (PT D):PT bath D was prepared in a similar manner to PT bath B by adding 18.9 liters of water to an empty 5 gallon plastic bucket. Hexafluorozirconic acid and copper solution were added to DI water. The bath pH and free fluoride were adjusted by using Chemfil buffer and Chemfos AFL, respectively. A single 1 gallon aliquot was removed and placed into a plastic cylinder with a magnetic stir bar. PT D was stirred on a magnetic stir plate at 300 RPM.

TABLE 2 group IVB pretreatment bath parameters for example 1

Pretreatment bath code	Zr(ppm)	Cu(ppm)	Free fluoride (ppm)	pH
					PT A
	200	35	90	4.8
					PT B	200	5	90	4.8
PT C	200	35	90	4.8
					PT D	200	5	90	4.8

Alkaline cleaner i (ac i):a rectangular stainless steel water tank with a total volume of 37 gallons, equipped with a spray nozzle, was filled with 10 gallons of deionized water. To which 5 is added00mL of Chemkleen 2010LP (a phosphate-free alkaline cleaner available from PPG industries, Inc.) and 50mL of Chemkleen 181ALP (a phosphate-free mixed surfactant additive available from PPG industries, Inc.). Alkaline cleaner I was used for all conditions in example 1.

Cold Rolled Steel (CRS) Test panels (4 ". times.12", project #28110, Audit grade, cut only, unpolished) were obtained from ACT Test Panel Technologies (Hillsdale, MI), Mich.). CRS panels were coated using one of three treatments (treatments A, B or C).

The procedures for treatment methods A, B and C are listed in tables 3, 4 and 5 below. For panels treated according to treatment method a, the panels were spray cleaned and degreased in alkaline cleaner IV (125 ° f) for 120 seconds at 10-15 psi using Vee spray nozzles, then rinsed by immersion in a deionized water bath (75 ° f) for 30 seconds, followed by deionized water spray rinsing using Melnor post-trigger 7-mode nozzles (available from Home Depot) set to shower mode for 30 seconds. The panel was then immersed in PT bath a or PT bath B at 80 ° f for 120 seconds without the application of electric current. After deposition, the panels were rinsed for 30 seconds by a deionized water spray rinse using a Melnor post-trigger 7-mode nozzle set to shower mode (75 ° F), and a spray rinse with deionized water was used

A high speed hand held blower (model 078302-300-000) was manufactured to dry with hot air (140 ° f) for 120 seconds at a high setting.

For panels processed according to process method B, the panels were cleaned in the same manner as process method a. The panels were then submerged in the specified pretreatment bath at 80 ° f for the specified time. A rectifier provided using DC produced a constant current density of-0.30 mA/cm2 under all conditions of process B. The rectifier is a Sorensen XG 300-5.6 (available from Ameteck, Bowen, Pa.). The current-assisted pre-treatment application conditions were a voltage set point of 20V, a ramp time of 0s, and the pre-treatment film thickness was controlled by time modulation, as defined in table 6. The steel plate was the cathode, and the anode was a stainless steel plate (3"× 8"). After pretreatment, the sequence of rinsing and drying for treatment B was the same as for treatment A

For panels processed according to process method C, the panels were cleaned in the same manner as process method a. The panels were then immersed in PT bath D at 80 ° f for 480 seconds or 900 seconds with no current applied. After pretreatment, the sequence of rinsing and drying for treatment C was the same as for treatment A.

TABLE 3 Process A

Step 1A	Alkaline cleaner (120 seconds, 125 ℃ F., spray application)
		Step 2A	Deionized Water rinse (30 seconds, 75 ℃ F., immersion application)
Step 3A	Deionized Water rinse (30 seconds, 75 ℃ F., spray application)
		Step 4A	Zirconium pretreatment (120 seconds, 80F., immersion application)
Step 5A	Deionized Water rinse (30 seconds, 75F., spray application)
		Step 6A	Hot air drying (120 seconds, 140 ℃ F.)

TABLE 4 treatment method B

Step 1B	Alkaline cleaner (120 seconds, 125F., spray application)
		Step 2B	Deionized Water rinse (30 seconds, 75 ℃ F., immersion application)
Step 3B	Deionized Water rinse (30 seconds, 75 ℃ F., spray application)
		Step 4B	Zirconium pretreatment (cathodic current, 80 ℃ F., immersion application)
Step 5B	Deionized Water rinse (30 seconds, 75F., spray application)
		Step 6B	Hot air drying (120 seconds, 140 ℃ F.)

TABLE 5 treatment method C

Table 6: treatment conditions for example 1

After completion of treatment process A, B or C, all panels were electrocoated with ED6107Z (a cathodic electrocoat where the components are commercially available as a two-component formulation from PPG), which ED6107Z was prepared by mixing 9829g of E6443 resin blend, 1599g of E6455Z paste blend, and 7571g of deionized water. The paint was ultrafiltered to remove 25% of the material, which was supplemented with 4749g of deionized water. The film thickness was time controlled to deposit a target film thickness of 0.6 mil +0.1 mil (15 microns +2 microns) on the pretreated steel plate. The DFT is controlled by varying the amount of charge (coulomb) that passes through the panel. Rectifiers (Xantrex model XFR600-2, Elkhart, Indiana, or Sorensen XG 300-5.6, Ameteck, Burwen, Pa.) are powered by DC power supplies. The electrocoat application conditions were a voltage set point of 200V, a ramp time of 30s, and a current density of-1.56 mA/cm 2. The electrocoat was maintained at 90 ° f. After electrocoat deposition, the panels were baked in an electric oven (Despatch model LFD-1-42) at 177 ℃ for 25 minutes.

The electrocoated panel was scribed with an X-shaped line. These were then submitted for 25 cycles of the Daimler Chrysler spallation corrosion test. The test was carried out according to the procedure described in the company DaimlerClise LP-463PB-52-01 variant B (published 11.11.2002). After the test was completed, loosely adhered paint and corrosion products were removed from the scratched area using Scotch 898 filament tape (available from 3M). For each condition, four panels were run. The average scratch creep is shown in table 7 below. Scratch creep refers to an area around a scratch where paint is lost due to corrosion or peeling (e.g., affected paint versus affected paint).

The faceplate for each condition was also analyzed by X-ray fluorescence using an Axios Max-Advance X-ray fluorescence (XRF) spectrophotometer (PANanytical, almolo, netherlands) to measure Zr and Cu coating weights. (A calibration curve was constructed and XRF peak intensities for Zr and Cu were correlated to Coating Weight (CW) determined by hydrochloric acid stripping method using ICP-OES)). The Zr/Cu ratio was then determined as the quotient of the Zr coating weight and the Cu coating weight. These results are reported in table 7.

TABLE 7 coating weight and Chrysler Corrosion test for example 1

As a result:applying the current to the pretreatment bath increased the Zr coating weight on the panel compared to the pretreatment bath without the current. For the pretreatment bath containing 35ppm Cu, table 7 shows that the panel treated according to treatment method a in pretreatment bath a without current had 46mg/m2 (condition code 1A), while the panel treated according to treatment method B in pretreatment bath C had 106mg/m2 Zr deposited (condition code 1F). For the pretreatment bath containing 5ppm Cu, Table 7 shows that the panels treated according to treatment method A in the currentless pretreatment bath B deposited 32mg/m²Zr (Condition code 1B), while the panel treated according to treatment B deposited 144mg/m²Zr (condition code 1G). The Zr deposition increased by a factor of 2.3 at higher copper levels and by a factor of 4.5 at lower copper levels. Without wishing to be bound by theory, the increased rate of hydroxide formation from the electrochemical decomposition of water is evidenced by an increase in the amount of (Zr) deposition by the flow of charge from the substrate into the pretreatment bath. The increased hydroxide formation enhances the formation of zirconium oxide and zirconium hydroxide at the substrate/pretreatment bath interface. Surprisingly, when comparing condition code 1A with condition code 1F and condition code 1B with condition code 1G, the rate of copper deposition is generally unaffected by the application of the cationic (reducing) deposition conditions. It would be expected that the rate of copper deposition would increase under cathodic conditions because of the presence of excess electrons which would reduce Cu (ii) in solution to Cu (0) or Cu (i), both of which could deposit onto a steel substrate. The results show that the amount of Cu deposition depends only on the copper concentration and is not influenced by the presence of the cathodic currentSounding; that is, higher bath levels increase the coating weight of copper in the pre-treated film. Furthermore, the scratch creep results reported in table 7 indicate that applying current improves the corrosion resistance of the steel in the cycle test, since both current-assisted deposition conditions are superior to the corresponding spontaneously deposited films.

Similar comparisons of Zr/Cu ratios can also be made between condition codes 1B, 1E and 1F. In all three cases, the Zr/Cu ratio was approximately 5 to 1. Under the spontaneous deposition condition (condition code 1B), the corrosion resistance was worse than that under the current assist pretreatment condition (condition code 1E or condition code 1F). Condition code 1E has the further advantage of reducing the deposition time (60 second immersion time) while still providing corrosion results comparable to condition code 1F (120 second immersion time). Whereas the pretreatment for most industrial applications is a time-limited process, the application of electric current provides the flexibility to allow sufficient pretreatment to be deposited to ensure acceptable corrosion resistance.

At the same Zr coating weight, two comparisons can be made between (i) condition code 1C and condition code 1F and (ii) condition code 1D and condition code 1G. In the former case (1C/1F), about 100mg/m was deposited²Zr of (2), and in the latter case (1D/1G), about 140mg/m was deposited²Zr (b) of (1). In both cases, the current-assisted deposition conditions result in less deposited Cu and improved corrosion protection. Without wishing to be bound by theory, the improved corrosion protection of the current assisted pretreatment deposition seen in comparing (i) and (ii) may be attributed to the reduction of copper incorporated into the film. When the Zr coating weight in the film was increased using the spontaneous deposition method, the corrosion performance was impaired (condition code 1C (100 mg/m)²Zr of 5.8mm average scratch creep) relative to condition code 1D (146mg/m2 Zr, 8.4mm average scratch creep)). This same effect was not observed in the pre-treated films generated under current-assisted conditions; corrosion Performance for Condition code 1F (106 mg/m)²Zr of 2.8mm, average scratch creep) and condition code 1G (144mg/m2 of Zr, 2.8mm average scratch creep) were the same. The difference in corrosion resistance depending on the deposition mechanism (spontaneous versus current-assisted) indicates that spontaneous deposition is due to impaired corrosion performanceThe thicker film of the volume has a higher intrinsic stress or porosity. Furthermore, this indicates that Zr pre-treatment deposited under cathodic bias inherently reduces film stress or that these films are denser at a given coat weight when compared to those deposited spontaneously.

EXAMPLE 2 Effect of Current Density on Zr/Cu ratio

Introduction:increasing the magnitude of the current density will increase the rate of hydrolysis of water, which in turn increases the concentration of hydroxide at the substrate/solution interface. In principle, depositing a zirconia pretreatment at higher current densities will increase the rate of Zr precipitation caused by a greater concentration of hydroxide.

Preparation of PT bath E (PT E):PT bath E was prepared in a similar manner to PT bath a by adding 18.9 liters of Deionized (DI) water to an empty 5 gallon plastic bucket. Hexafluorozirconic acid and copper solution were added to DI water. The bath pH and free fluoride were adjusted by using Chemfil buffer and Chemfos AFL, respectively. Table 8 shows pretreatment bath parameters for PT bath E. For each of the conditions listed in table 10 below, a fresh 30mL aliquot of the solution of PT bath E was used.

TABLE 8 IVB pretreatment bath parameters for example 2

Pretreatment bath code	Zr(ppm)	Cu(ppm)	Free fluoride (ppm)	pH
					PT E
	200	35	90	4.8

Alkaline cleaner ii (ac ii):a rectangular stainless steel water tank with a total volume of 37 gallons, equipped with a spray nozzle, was filled with 10 gallons of deionized water. To this was added 500mL of Chemkleen SP1 (an alkaline cleaner available from PPG industries, Inc.) and 50mL of Chemkleen 185ALP (a mixed surfactant additive available from PPG industries, Inc.). For all conditions in example 2, alkaline cleaner II was used.

Cold Rolled Steel (CRS) test panels (70mm by 150mm by 0.8mm, project #26920, Audit grade, cut only, unpolished) were obtained from ACT test panel technology Inc. (Hilsbad, Mich.). CRS panels were coated using treatment D or E.

The pretreatment of the panel was performed with or without a cathode bias using the pretreatment apparatus shown in fig. 2. Referring to fig. 2, a pretreatment apparatus 200 includes an anode 210 of stainless steel plate and a base material 220 of Cold Rolled Steel (CRS) plate separated by a Polytetrafluoroethylene (PTFE) gasket 230. The panel is secured to the washer using a black binder clip (not shown). In all cases, the deposition was carried out for 30 seconds.

The procedures for processing methods D and E are listed in tables 9 and 10 below. For panels treated according to treatment method D, the panels (substrates 220) were spray cleaned and degreased in alkaline cleaner IV (125 ° f) for 120 seconds using Vee spray nozzles at 10-15 psi, then rinsed by immersion in a deionized water bath (75 ° f) for 30 seconds, followed by deionized water spray rinsing using Melnor post-trigger 7-mode nozzles (available from family jewels) set to shower mode for 30 seconds. The apparatus described in fig. 2 was then assembled and 30mL of PT bath E was added to the empty space. Exposure to the solution was continued for 30 seconds and the assembly was disassembled. Post-trigger 7-mode nozzle with Melnor set to shower mode (75 ° F) through deionized waterSpray rinsing CRS Panels (substrate 220) were rinsed for 30 seconds and used

A high speed hand held blower (model 078302-300-000) was manufactured to dry with hot air (140 ° f) for 120 seconds at a high setting.

For the panel (substrate 220) treated according to treatment method E, the panel was cleaned in the same manner as treatment method D. The panels were exposed to the pretreatment solution in the same manner except that the current was applied under all conditions of treatment method E. Specific current densities are shown in table 11. After pretreatment, the sequence of rinsing and drying for treatment E was the same as for treatment D

TABLE 9 treatment method D

TABLE 10 treatment method E

Step 1E	Alkaline cleaner (120 seconds, 125 ° f, immersion application)
		Step 2E	Deionized Water rinse (30 seconds, 75 ℃ F., immersion application)
Step 3E	Deionized Water rinse (30 seconds, 75F., spray application)
		Step 4E	Assembly coating device
Step 5E	Zirconium pretreatment (30 seconds exposure at 80 ℃ F., cathodic bias with variable current density)
		Step 6E	Coating disassembling device
Step 7E	Deionized Water rinse (30 seconds, 75 ℃ F., spray application)
		Step 8E	Hot air drying (120 seconds, 140 ℃ F.)

TABLE 11 treatment conditions for example 2

The panel (substrate 220) for each condition was also analyzed by the lift-off method. Samples (6 cm. times.6 cm) of the pretreated panel were cut. The sample was exposed to 25mL of 6N hydrochloric acid for 5 minutes to dissolve the pretreatment layer. The solution was submitted for ICP-OES and the Cu and Zr concentrations were measured. These were converted to coating weights (mg/m) for each condition. The coating weight results are shown in table 12. The Zr/Cu ratio was then determined by taking the quotient of the Zr coating weight and the copper coating weight. These results are also reported in table 12.

TABLE 12 coating weights and Zr/Cu ratios for example 2

As a result:the current density changes the Zr deposition rate and the Zr/Cu ratio of the pretreatment coating. FIG. 3 is a graph showing the effect of current density on zirconium deposition according to the method described in example 2, where "Zr CW" represents the zirconium coating weight. FIG. 4 is a graph showing the effect of current density on zirconium/copper deposition according to the method described in example 2, where "Zr CW/Cu CW" represents the quotient of the zirconium coating weight and the copper coating weight, both expressed in milligrams per square meter. Despite the fact that high current densities increase the hydrolysis rate of water, there is an optimum for the deposition of Zr. When the current density is changed from 0 to-0.6 mA/cm²The rate of Zr deposition increases. However, the rate of Zr deposition was from-1.0 mA/cm²To-15 mA/cm²And decreases. A similar trend was also observed for the Zr/Cu ratio.

When an electric field is applied to both panels, the species in solution will migrate based on their surface charge. Species in solution having a positive charge will flow towards the cathode, while species having a negative charge will migrate towards the anode. At the surface of each electrode, a bilayer is formed which will control the migration of these species towards the respective electrode. As the current density increased, the rate of Zr deposition decreased. Without wishing to be bound by theory, the results of example 2 suggest that the Zr species in the solution are negatively charged and that the strength of the bilayer at the substrate/bath interface reduces the efficiency of Zr deposition at the cathode. In addition, the negative surface charge of the Zr species in the solution will be preferentially attracted to the positively charged anode. Therefore, the current density must be balanced to allow for efficient deposition while overcoming the electric field assisted migration of the Zr species in solution.

EXAMPLE 3 Effect of applying Current to pretreatment baths of different Zr/electropositive Metal ratios relative to No Current applied

Preparation of PT bath F (PT F):PT bath F was prepared by adding 4500 ml of Deionized (DI) water to an empty two-gallon plastic bucket. Potassium hexafluorozirconate was added to the DI water. Additionally, 3026 ml of deionized water was added to an empty 1 gallon plastic bucket. Potassium chromium (III) sulfate was added to DI water. Adding a magnetic stirring rod into each containerThe solution was stirred on a magnetic stir plate at 300RPM until the zirconium and chromium dissolved. The solutions were mixed and the pH was adjusted by using dilute sulfuric acid solution.

Preparation of PT bath G (PT G):PT bath G was prepared in a similar manner to PT bath a by adding 896 ml of Deionized (DI) water to an empty half gallon plastic bucket. Potassium hexafluorozirconate was added to the DI water. In addition, 600 ml of deionized water was added to an empty 1 quart plastic bucket. Potassium chromium (III) sulfate was added to the DI water, with the final concentration of chromium in the pretreatment bath being lower than in PT bath F. With the addition of a magnetic stir bar to each vessel, the solution was stirred on a magnetic stir plate at 300RPM until the zirconium and chromium were dissolved. The Zr and Cr solutions were mixed and the pH was adjusted by using a dilute sulfuric acid solution.

Preparation of PT bath H (PT H):PT bath H was prepared in a manner similar to PT bath a by adding 896 ml of Deionized (DI) water to an empty half gallon plastic bucket. Potassium hexafluorozirconate was added to the DI water. In addition, 600 ml of deionized water was added to an empty 1 quart plastic bucket. Potassium chromium (III) sulfate was added to the DI water, with the final concentration of chromium in the pretreatment bath being lower than that in PT bath G. With the addition of a magnetic stir bar to each vessel, the solution was stirred on a magnetic stir plate at 300RPM until the zirconium and chromium dissolved. The Zr and Cr solutions were mixed and the pH was adjusted by using a dilute sulfuric acid solution.

TABLE 13 group IVB pretreatment bath parameters for example 3

Pretreatment bath code	Zr(ppm)	Cr(ppm)	Free fluoride (ppm)	pH
					PT F	483	255	Not measured	3.12
PT G	483	120	7	3.25
					PT H	483	97	7	3.27

Alkaline cleaner iii (ac iii):AC III consists of Bonderite C-AK 298AERO (known as Ridoline 298) available from Henkel, Madison Heights, Mich. AC III was prepared and maintained according to the manufacturer's instructions. Alkaline cleaner III was used for all conditions in example 3.

Deoxidizer bath i (db i):DB I consists of Turco deoxidizer 6/16, available from Hangao (Medison, Mich.). DB I is prepared and maintained according to the manufacturer's instructions. Deoxidizer I was used under all conditions in example 3.

Aluminum test panels (2 "x 3" uncoated 2024T3 alloy/temper) were obtained from Bralco Metals (Wichita, KS, kansas). The aluminum panels were coated using one of two treatment methods (treatment methods F and G).

The procedures for handling methods F and G are set forth in tables 14 and 15 below. For panels treated according to treatment method F, the panels were immersion cleaned and degreased in alkaline cleaner III (130 ° F) for 120 seconds, then rinsed by immersion in a tap water bath (75 ° F) for 60 seconds, followed by rinsing with a tap water spray bottle for 10 seconds. The panels were then soaked in deoxidizer I (75F.) for 150 seconds, then rinsed by soaking in a tap water bath (75F.) for 60 seconds, followed by rinsing with a deionized water spray bottle (75F.) for 10 seconds. The panels were then immersed in PT bath F, PT bath G or PT bath H at 75 ° f for different times without the application of electric current. After deposition, the panels were rinsed by soaking in two successive deionized water baths for 120 seconds each, followed by rinsing with a deionized water spray bottle for 10 seconds. The panel was allowed to dry completely at ambient conditions.

For the panel treated according to treatment method G, the panel was cleaned and deoxidized in the same manner as in treatment method F. The panels were then immersed in the specified pretreatment bath at 75 ° f for the specified time. The constant current densities listed in table 16 were generated for all conditions of treatment method G using a rectifier supplied by DC (Xantrex model XFR600-2, erechhart, indiana, or Sorensen XG 300-5.6, ametech, berween pennsylvania). The current-assisted pre-treatment application conditions were a voltage set point of 10V, a ramp time of 0s, and the pre-treatment film thickness was controlled by time modulation, with the specific details defined in table 16. The aluminum panel was the cathode and the anode was two stainless steel plates (1 "x 4" each). After pretreatment and rinsing, treatment G was dried as in treatment F.

TABLE 14 Process F

Step 1F	Alkaline cleaner (120 seconds, 130 ℃ F., immersion application)
		Step 2F	Tap Water rinse (60 seconds, 75 ℃ F., immersion application)
Step 3F	Tap Water rinse (10 seconds, 75 ° F, spray bottle application)
		Step 4F	Deoxidizer (150 seconds, 75 ° f, immersion application)
Step 5F	Tap Water rinse (60 seconds, 75 ℃ F., immersion application)
		Step 6F	Deionized Water rinse (10 seconds, 75 ℃ F., spray bottle application)
Step 7F	Zirconium pretreatment (variable time, 75 ℃ F., immersion application)
		Step 8F	Deionized Water rinse (120 seconds, 75 ℃ F., immersion application)
Step 9F	Deionized Water rinse (120 seconds, 75 ℃ F., immersion application)
		Step 10F	Deionized Water rinse (10 seconds, 75 ℃ F., spray bottle application)
Step 11F	Air drying (ambient)

TABLE 15 processing method G

		Step 1G	Alkaline cleaner (120 seconds, 130 ℃ F., immersion application)
Step 2G	Tap Water rinse (60 seconds, 75F., immersion application)
		Step 3G	Tap Water rinse (10 seconds, 75F., spray bottle application)
Step 4G	Deoxidizer (150 seconds, 75 ° f, immersion application)
		Step 5G	Tap Water rinse (60 seconds, 75 ℃ F., immersion application)
Step 6G	Deionized Water rinse (10 seconds, 75 ℃ F., spray bottle application)
		Step 7G	Zirconium pretreatment (cathodic current, 75 ℃ F.; immersion application)
Step 8G	Deionized Water rinse (10 seconds, 75 ℃ F., spray bottle application)
		Step 9G	Air drying (ambient)

The pretreated panels were then submitted for an unpainted neutral salt spray corrosion test for 336 hours. After the test was completed, the entire panel surface was visually inspected for corrosion sites ("pits") on the panel. When white corrosion products are present, pits are considered any corrosion event. One panel was run for each condition. Table 16 below shows the number of pits.

TABLE 16 treatment conditions and Corrosion results for example 3

As a result:applying the current to the pretreatment bath improves the unpainted neutral salt fog corrosion resistance compared to a pretreatment bath without the current. For the pretreatment baths containing a 1.9Zr/Cr ratio (225ppm Cr), table 16 shows that the panel treated according to treatment method F in the currentless pretreatment bath F (condition code 3A) had 18 pits, while the panel treated according to treatment method G in the currentless pretreatment bath F (condition codes 3J and 3K) had 3 pits and 0 pit. For pretreatment baths in which the Zr/Cr ratio was increased to 4/1, table 16 shows that the panel treated according to treatment method F had 27 pits in the currentless pretreatment bath G (condition code 3B), and the panel treated according to treatment method G had 2 pits and 0 pits in the currentless pretreatment bath G (condition codes 3O and 3P). For pretreatment baths in which the Zr/Cr ratio was increased to 5/1, table 16 shows that the panel treated according to treatment method F had 13 pits in the currentless pretreatment bath H (condition code 3B), and the panel treated according to treatment method G had 0 pits in the currentless pretreatment bath G (condition codes 3Q and 3R).When the panel was treated according to the treatment method F with increased immersion time (condition codes 3C, 3D, 3E, 3G, 3H and 3I) in the pretreatment bath G or H without current, the number of pits was in the range of 12 to 25, compared to when the panel was treated according to the treatment method G with increased immersion time (condition codes 3Q, 3R, 3U and 3V) in the pretreatment bath G or H with current, the number of pits was in the range of 0 to 1.

EXAMPLE 4 Effect of soak time on filiform Corrosion

Preparation of zirconium pretreatment composition:the pretreatment composition of example 4 was prepared in the same manner as described in example 1 using the same chemicals. The exact bath parameters are recorded in table 17.

Preparation of PT bath I (PT I):PT bath I was prepared in a manner similar to PT bath a by adding 18.9 liters of water to an empty 5-gallon plastic bucket. Hexafluorozirconic acid and copper solution were added to DI water. The bath pH and free fluoride were adjusted by using Chemfil buffer and Chemfos AFL, respectively.

TABLE 17 pretreatment bath parameters for example 4

Pretreatment bath code	Zr(ppm)	Cu(ppm)	Free fluoride (ppm)	pH
					PT I	175	32	99	4.7

Alkaline cleaner iv (ac iv):the cleaner was prepared in the same manner as aci. A rectangular stainless steel water tank with a total volume of 37 gallons, equipped with a spray nozzle, was filled with 10 gallons of deionized water. To this was added 500mL of Chemkleen 2010LP (a phosphate-free alkaline cleaner available from PPG industries) and 50mL of Chemkleen 181ALP (a phosphate-free mixed surfactant additive available from PPG industries). Alkaline cleaner IV was used to prepare the panels for the conditions tested in example 4.

Aluminum panels (AA6022T43, 04X12X035 cut only, unpolished, item # APR39007) were purchased from ACT and cut to 10cm X15 cm prior to pretreatment. The bottom portion of the aluminum panel was ground when the panel was ready for filiform testing. On the aluminum panels, the bottom 7.5 cm of each panel was sanded with 3M available P320 sandpaper, which was used on a6 "random orbital palm sander (Advanced Tool Design) model-ATD-2088 available from ATD. Grinding is used to help determine any differences in corrosion performance of the ground and unground portions of the metal. Sanding is used in the field as a means to increase adhesion of the subsequently painted surface and to eliminate potential defects that may penetrate into the upper layers of the coating stack (e.g., the topcoat layer). Sanding will typically expose intermetallic compounds, which will increase the tendency of the substrate (especially aluminum) to experience accelerated corrosion. Thus, the improved corrosion resistance of ground aluminum is of great value to automotive manufacturers.

The panels were treated using treatment methods H or I as outlined in tables 18 and 19 below. For panels treated according to treatment method H, panels were spray cleaned and degreased in alkaline cleaner IV (125 ° f) for 120 seconds at 10-15 psi using Vee spray nozzles, then rinsed by immersion in a deionized water bath (75 ° f) for 30 seconds, followed by deionized water spray rinsing using Melnor post-trigger 7-mode nozzles (available from family jewels) set to shower mode. Immersing all panels inPT I120 seconds (80F.), 7-mode nozzle post-activated using Melnor set to shower mode (75F.), flush panel by deionized water spray flush for 30 seconds, and use

A high speed hand held blower (model 078302-300-000) was manufactured to dry with hot air (140 ° f) for 120 seconds at a high setting.

For panels treated according to treatment method I, the panels were cleaned, pretreated and rinsed as in method H except that a cathodic current was applied to the panels during the application of PT I. The current densities used during the pretreatment process are shown in table 20. After pretreatment and subsequent DI rinsing, use

A high speed hand held blower (model 078302-300-000) was manufactured to dry the panel with hot air (140 ° f) for 120 seconds at a high setting.

The coating weights as determined by XRF, as described herein, are shown in table 22.

TABLE 18 Process H

Step 1H	Alkaline cleaner (120 seconds, 125 ℃ F., spray application)
		Step 2H	Deionized Water rinse (30 seconds, 75 ℃ F., immersion application)
Step 3H	Deionized Water rinse (30 seconds, 75 ℃ F., spray application)
		Step 4H	Zirconium pretreatment (120 seconds, 80F., immersion application)
Step 5H	Deionized Water rinse (30 seconds, 75 ℃ F., spray application)
		Step 6H	Hot air drying (120 seconds, 140 ℃ F.)

TABLE 19 Process I

Step 1I	Alkaline cleaner (120 seconds, 125 ℃ F., spray application)
		Step 2I	Deionized Water rinse (30 seconds, 75 ℃ F., immersion application)
Step 3I	Deionized Water rinse (30 seconds, 75 ℃ F., spray application)
		Step 4I	Zirconium pretreatment (cathodic current, 120 seconds, 80 ℃ F., immersion application)
Step 5I	Deionized Water rinse (30 seconds, 75 ℃ F., spray application)
		Step 6I	Hot air drying (120 sec, 140 ℃ F.)

Table 20 pretreatment conditions for example 4.

Condition code	Detergent bath	PT compositions	Current density	Electrodeposition time	Total immersion time
						4A	AC IV	PT I	N/A	0s	30s
4B	AC IV	PT I	-0.30mA/cm2	30s	30s
						4C	AC IV	PT I	N/A	0s	120s
4D	AC IV	PT I	-0.30mA/cm2	120s	120s
						4E	AC IV	PT I	N/A	0s	300s
4F	AC IV	PT I	-0.30mA/cm2	300s	300s

After completion of treatment H or I, all panels were electrocoated with ED7000Z (a cathodic electrocoat, the components of which are commercially available from PPG), which ED7000Z was prepared by mixing E6433Z resin (6116.70 grams), E6434Z paste (1073.37 grams) and deionized water (4810.50 grams). The paint was ultrafiltered to remove 25% of the material, which was supplemented with fresh deionized water. The paint was applied in the same manner as described in the conditions of example 1.

The electrocoated panels were subjected to a filiform corrosion test (modified EN 3665). The electrocoated panels were scored with vertical lines (3-4 inches). The panels were then exposed to hydrochloric acid vapor for one hour while being stored in a vertical position. After HCl vapor exposure, the panels were aged on plastic racks for 12 weeks in a cabinet maintained at 80% humidity and 40 ℃. The corrosion results are shown in table 21 below. The panels subjected to EN3665 modification were evaluated by measuring the average of the lengths of the five longest filaments (reported in mm) without removing loosely adhering paint by external means (e.g. sandblasting).

Table 21 corrosion results on aluminum of example 2.

A minimal corrosion/filiform formation was observed on the unground area of the panel. The longest filiform line is present on the polished area coated with aluminum.

The B-edge corrosion was qualitatively determined on a scale of 1-5. A rating of 1 indicates the smallest edge filament and a rating of 5 indicates the formation of a filament at the edge.

Table 22. coating composition on aluminum for example 4 conditions.

As a result:the application of the current reduces the formation of filiform corrosion at the score lines and at the edges of the treated panel. The improvement in corrosion can be attributed to the increase in the observed Zr CW/Cu CW ratio when comparing the passive and electrochemically assisted deposition processes. Reducing copper deposition is very important for aluminum because high (higher) levels of deposited Cu may reduce the corrosion resistance of pre-treated and electrocoated panels.

Example 5: the use of applied current improves the performance of the welded and heat affected zone.

Introduction:in automotive manufacturing and industrial construction, welding is used as a way to join steel and other materials. High temperature for welding can alter the crystal of the steelBulk structure, which may alter the reactivity of the material to pretreatment. Furthermore, the high heat, flux and presence of oxygen often result in the formation of thick iron/metal oxides in the joint region. These areas are difficult to pre-treat and typically require the application of an acidic etch to remove the rust. Zinc phosphate at a pH of about 3 is more effective at removing rust than group IVB pretreatments that tend to have a pH greater than 4. It would be desirable to modify the group IVB application process to deposit a pretreatment for the weld rust.

Preparation of zirconium pretreatment composition:the pretreatment composition of example 5 was prepared in the same manner as described in example 1 using the same chemicals. The exact bath parameters are recorded in table 23.

Preparation of PT bath J (PT J):PT bath I was prepared in a similar manner to PT bath a by adding 3.8 liters of water to an empty 1 gallon plastic bucket. Hexafluorozirconic acid and copper solution were added to DI water. The bath pH and free fluoride were adjusted by using Chemfil buffer and Chemfos AFL, respectively.

Preparation of zirconium control bath (PT ZC):a one gallon solution of ZircoBond II, a zirconium-containing pretreatment composition available from PPG industries, was prepared according to the manufacturer's instructions. The bath had a pH of 4.7 and contained 175ppm zirconium, 30ppm copper, 75ppm molybdenum and 85ppm free fluoride.

Activating and washing zinc phosphate:versabond rinse conditioner (zinc phosphate based material) was obtained from PPG industries. An activation rinse bath was prepared by adding 1.1 grams of Versabond RC concentrate to each liter of deionized water to give an activator bath with a zinc phosphate concentration of 0.5 grams/liter.

Preparation of zinc phosphate control bath (PT ZnP):chemfos 700AL (CF 700AL) zinc phosphate pretreatment baths were produced by filling approximately three quarters of a 5 gallon container with deionized water according to the manufacturer's instructions. To this was added 700ml of Chemfos 700A, 1.5ml of Chemfos FE, 51ml of Chemfos AFL and 350ml of Chemfos 700B (all commercially available from PPG). To this was added 28.6 grams of zinc nitrate hexahydrate and 2.5 grams of sodium nitrite (both available from Feishell scientific Co., Ltd.)) And operating the free acid in the bath at 0.7-0.8 points free acid, 15-19 points total acid, and 2.2-2.7 gas points (mL). To obtain the correct amount of free and total acids, adjustments were made using Chemfos 700B according to the product data sheet. The temperature of the bath was 125 ° f and the panel was immersed in the bath for 2 minutes.

TABLE 23 IVB pretreatment bath parameters for example 5

Alkaline detergent V (AC V): a rectangular stainless steel water tank with a total volume of 37 gallons, equipped with a spray nozzle, was filled with 10 gallons of deionized water. To this was added 500mL of Chemkleen 2010LP (a phosphate-free alkaline cleaner available from PPG industries) and 50mL of Chemkleen 181ALP (a phosphate-free mixed surfactant additive available from PPG industries). Alkaline cleaner V was used for all conditions in example 5.

Alkaline cleaner vi (ac vi):a 5 gallon bucket was filled with 5 gallons of deionized water. To this was added 250mL of Chemkleen 2010LP (a phosphate-free alkaline cleaner available from PPG industries), and 25mL of Chemkleen 181ALP (a phosphate-free mixed surfactant additive available from PPG industries). The immersion heater was placed in a bucket and the alkaline solution was heated to 125 ° f. The immersion heater is set to a "high" setting. For all conditions in example 5, alkaline cleaner VI was used after AC V.

Spangler panels as shown in FIG. 5 were obtained from Laser Precision (Kattpeller part number 381-. The base plate 300 is comprised of two Cold Rolled Steel (CRS) panels (a flat or back panel 310 and an inset panel 320) that are welded together by four spot welds 330 and one seam weld 340. The galvanized nut 350 is welded to the flat plate 310. In addition, there are three laser-cut holes (two circles 360 and one rectangle 370). The method of joining the flat plate 310 and the inset panel 320 is accomplished using high temperatures that will alter the crystal structure of the steel, resulting in a "heat affected zone". The panels were treated with current-assisted deposition treatment J, Zircobond II comparative treatment K, and zinc phosphate control treatment L, and their respective coatings were evaluated.

The panels were treated using treatment method J, K or L, as shown in tables 24, 25, and 26 below. For panels treated according to treatment method J, panels were spray cleaned and degreased using Vee spray nozzles at 10psi-15psi in alkaline cleaner V (125 ° f) for 60 seconds, then immersed in alkaline cleaner VI with high speed agitation at 125 ° f for 120 seconds. The panel was then rinsed by immersion in a deionized water bath (75 ° f) for 30 seconds, followed by a deionized water spray rinse for 30 seconds using a Melnor post-trigger 7-mode nozzle (available from homecare corporation) set to shower mode. The panel was then immersed in PT J for 120 seconds (80 ° f) and a cathodic current was applied. After deposition, the panels were rinsed for 30 seconds by a deionized water spray rinse using a Melnor post-trigger 7-mode nozzle set to shower mode (75 ° F), and a spray rinse with deionized water was used

A high speed hand held blower (model 078302-300-000) was manufactured to dry with hot air (140 ° f) for 120 seconds at a high setting.

For panels treated according to treatment method K (zirconium control), the panels were cleaned in the same manner as treatment method J. The panel was then immersed in PT ZC at 80 ° f for 120 seconds (no current applied). After pretreatment, the sequence of rinsing for treatment method K was the same as treatment method J.

For the panels treated according to treatment method L (zinc phosphate control), the panels were cleaned in the same manner as in treatment method J. The panels were then immersed in the activator for 60 seconds at ambient temperature and then transferred to a zinc phosphate bath (PT ZnP) at 125 ° f for 120 seconds. After pretreatment, the sequence of rinsing for treatment method L was the same as treatment method J.

TABLE 24 Process J

Step 1J	Alkaline cleaner (60 seconds, 125 ℃ F., spray application)
		Step 2J	Alkaline cleaner (120 seconds, 125 ° f, immersion application)
Step 3J	Deionized Water rinse (30 seconds, 75 ℃ F., immersion application)
		Step 4J	Deionized Water rinse (30 seconds, 75F., spray application)
Step 5J	Zirconium pretreatment (cathodic current, 120 seconds, 80 ℃ F., immersion application)
		Step 6J	Deionized Water rinse (30 seconds, 75F., spray application)
Step 7J	Hot air drying (120 seconds, 140 ℃ F.)

TABLE 25 Process K

Step 1K	Alkaline cleaner (60 seconds, 125 ℃ F., spray application)
		Step 2K	Alkaline cleaner (120 seconds, 125 ° f, immersion application)
Step 3K	Deionized Water rinse (30 seconds, 75 ℃ F., immersion application)
		Step 4K	Deionized Water rinse (30 seconds, 75 ℃ F., spray application)
Step 5K	Zirconium control pretreatment (PT ZC, 120 seconds, 80 ℃ F., immersion application)
		Step 6K	Deionized Water rinse (30 seconds, 75F., spray application)
Step 7K	Hot air drying (120 seconds, 140 ℃ F.)

TABLE 26 treatment method L

Step 1L	Alkaline cleaner (60 seconds, 125 ℃ F., spray application)
		Step 2L	Alkaline cleaner (120 seconds, 125 ° f, immersion application)
Step 3L	Deionized Water rinse (30 seconds, 75 ℃ F., immersion application)
		Step 4L	Deionized Water rinse (30 seconds, 75 ℃ F., spray application)
Step 5L	Rinse conditioner (60 seconds, 75 ° f, immersion application)
		Step 6L	Zinc phosphate control pretreatment (PT ZnP, 120 seconds, 125 ℃ F., immersion application)
Step 7L	Deionized Water rinse (30 seconds, 75 ℃ F., spray application)
		Step 8L	Hot air drying (120 sec, 140 ℃ F.)

Table 27. treatment conditions for example 5.

Condition	Detergent bath	Pretreatment composition	Application of electric current	Current Density (mA/cm)2)	Processing method
						5A	AC V/AC VI	PT J	Is that	-0.3mA/cm2	Method J
5B	AC V/AC VI	PT J	Is that	-0.6mA/cm2	Method J
						5Z	AC V/AC VI	PT ZC	Whether or not	N/A	Method K
5P	AC V/AC VI	PT ZnP	Whether or not	N/A	Method L

After treatment J, K or L was complete, all panels were electrocoated with ED7000Z (a cathodic electrocoat, the components of which are commercially available from PPG), which ED7000Z was prepared by mixing E6433Z resin, E6434Z paste, and deionized water as described above. The paint was ultrafiltered to remove 25% of the material, which was supplemented with fresh deionized water. The electrocoat was applied in the manner described above, with the target film thicknesses of the flat panel and the inset panel each being 0.6 mils+0.1 mil. The DFT is controlled by varying the amount of charge (coulomb) that passes through the panel. After deposition of the electrocoat, the panels were baked in an oven (Despatch model LFD-1-42) at 177 ℃ for 25 minutes.

The electrocoated panels are scribed on the flat panel and the inset welded panel. The panel was submitted for GMW14872 testing for 40 cycles. The conditions are described in table 28. After the corrosion test, the panels were media blasted (MB-2, an irregular granular plastic grain with a Mohs hardness of 3.5 and a size range of 0.58mm to 0.84mm, available from Maxi-Blast, Inc., South Bend, Indiana) using an in-line delivery system IL-885 sandblaster (input air pressure 85psi, Imperial grinding Equipment Company, model information: IL885-M9655) after the corrosion test to remove loosely adhered paint and corrosion products. For each corrosion test, one panel was run under each condition. The average scratch creep for the flat panel and the embedded panel is shown in table 29. Scratch creep refers to the area around a scratch where paint is lost due to corrosion or peeling (e.g., affected paint versus affected paint).

Table 28 corrosion testing of the electrocoated Spangler panels used in example 5.

Corrosion testing	Base material	Scratch mark	Test length	Type of corrosion
					GMW14872	Spangler (Steel)	Vertical line	40 cycles	Air bubble

Table 29 corrosion results from GM14872 corrosion test of example 5.

As a result:application of the current improves group IVB deposition in the non-reactive heat affected zone. Comparison of standard pretreatments (zinc phosphate and group IVB controls) demonstrates the challenge of treating the heat affected zone (relatively large scratch creep on the inset panel). Using-0.3 mA/cm²Or-0.6 mA/cm²Corrosion results were provided on both the flat panel and the weld insert panel over the zinc phosphate control. These results are significant because they provide an improvement in corrosion protection for group IVB over zinc phosphate, although higher pH (4.7) will not remove a significant amount of the rust.

Claims (44)

1. A method for treating a substrate, comprising:

contacting the substrate with a pretreatment composition comprising a group IVB metal and an electropositive metal; and

passing an electric current between an anode and the substrate acting as a cathode to deposit a coating on the substrate from the pretreatment composition.

2. The method of claim 1, wherein the group IVB metal comprises zirconium.

3. The method of claim 1 or claim 2, wherein the electropositive metal comprises copper.

4. The method of claim 1 or claim 2, wherein the electropositive metal comprises trivalent chromium.

5. The method of any preceding claim, wherein the pretreatment composition further comprises fluoride ions.

6. The method of any one of the preceding claims, wherein the group IVB metal is in a range of 4 to 40 times the amount of the electropositive metal by weight.

7. The method of claim 1, claim 5, or claim 6, wherein the group IVB metal comprises zirconium and the electropositive metal comprises copper.

8. The method of claim 7, wherein the coating comprises a weight ratio of the group IVB metal to the electropositive metal greater than 4: 1.

9. The method of any preceding claim, wherein the current comprises | -1| milliamp/square centimeter (mA/cm)²) Or a smaller current density.

10. The method of any preceding claim, wherein the current density comprises | -0.6| milliamps/square centimeter (mA/cm)²) Or a smaller current density.

11. The method of any preceding claim, wherein the substrate comprises steel.

12. The method of any one of claims 1 to 10, wherein the substrate comprises aluminum.

13. The method of any one of the preceding claims, wherein the substrate comprises a portion of a vehicle.

14. The method of any preceding claim, wherein the coating has properties that provide corrosion resistance to the substrate.

15. The method of claim 14, wherein the corrosion resistance is filiform corrosion resistance.

16. A substrate treated by the method of any one of the preceding claims.

17. A method for treating an electrically conductive substrate, comprising:

contacting the electrically conductive substrate with a pretreatment composition comprising a group IVB metal and an electropositive metal; and

electrodepositing a coating on the conductive substrate from the pretreatment composition.

18. The method of claim 17, wherein the group IVB metal in the pretreatment composition is in a range of 4 to 40 times the amount of the electropositive metal by weight.

19. The method of claim 17 or claim 18, wherein the electropositive metal comprises copper.

20. The method of claim 17 or claim 18, wherein the group IVB metal comprises zirconium and the electropositive metal comprises copper.

21. The method of any one of claims 17-20, wherein the coating comprises a ratio of the group IVB metal to the electropositive metal of greater than 4: 1.

22. The method of claim 17 or claim 18, wherein the electropositive metal comprises trivalent chromium.

23. The method of any one of claims 17 to 22, wherein electrodepositing comprises passing an electric current between an anode, the conductive substrate, and the pretreatment composition.

24. The method of claim 23, wherein the current comprises | -1| milliamps per square centimeter (mA/cm)²) Or a smaller current density.

25. The method of claim 23, wherein the current comprises | -0.6| milliamps/square centimeter (mA/cm)²) Or a current density of a smaller current density.

26. The method of any one of claims 17 to 25, wherein the substrate comprises steel.

27. The method of any one of claims 17 to 25, wherein the substrate comprises aluminum.

28. The method of any one of claims 17 to 25, wherein the substrate comprises a portion of a vehicle.

29. The method of any one of claims 17 to 28, wherein the coating has properties that provide corrosion resistance to the substrate.

30. The method of claim 29, wherein the corrosion resistance is filiform corrosion resistance.

31. A substrate treated by the method of any one of claims 17 to 30.

32. A method for treating an electrically conductive substrate, comprising:

contacting an electrically conductive substrate with a pretreatment composition comprising a group IVB metal and an electropositive metal; and

electrodepositing a coating on the electrically conductive substrate from the pretreatment composition, wherein the coating comprises each of the group IVB metal and the electropositive metal.

33. The method of claim 32, wherein the group IVB metal comprises zirconium and the electropositive metal comprises copper.

34. The method of claim 32 or claim 33, wherein the weight ratio of the group IVB metal to the electropositive metal is greater than 4: 1.

35. The method of claim 32, wherein the electropositive metal comprises trivalent chromium.

36. The method of claim 32, wherein the group IVB metal comprises zirconium and the electropositive metal comprises trivalent chromium.

37. The method of any one of claims 32 to 36, wherein electrodepositing comprises passing an electric current at | -1| milliamps per square centimeter (mA/cm)²) Or lower current density, between the anode, the substrate, and the pretreatment composition.

38. The method of any one of claims 32 to 36, wherein electrodepositing comprises passing an electric current at | -0.6| milliamps/square centimeter (mA/cm)²) Or lower current density through the substrate and the pretreatment composition.

39. The method of any one of claims 32 to 38, wherein the substrate comprises steel.

40. The method of any one of claims 32 to 38, wherein the substrate comprises aluminum.

41. The method of any one of claims 32-38, wherein the substrate comprises a portion of a vehicle.

42. The method of any one of claims 32 to 38, wherein the coating has properties that provide corrosion resistance to the substrate.

43. The method of claim 42, wherein the corrosion resistance is filiform corrosion resistance.

44. A substrate treated by the method of any one of claims 32 to 43.

Images