AU711181B2 - Precoat conditioning treatment for autodeposition - Google Patents

Description

WO 97/09127 PCT/US96/13480 Description PRECOAT CONDITIONING TREATMENT FOR AUTODEPOSITION FIELD OF THE INVENTION This invention relates to the use of liquid, usually aqueous, solutions or dispersions in which active metal surfaces of inserted objects are coated with an adherent polymer film that increases in thickness the longer the metal object remains in the bath, even though the liquid is stable for a long time against spontaneous precipitation or flocculation of any solid polymer, in the absence of contact with active metal, metal that spontaneously begins to dissolve at a substantial rate when introduced into the liquid solution or dispersion. Such compositions, and processes of forming a coating on a metal surface using such compositions, are commonly denoted in the art, and in this specification, as "autodeposition" or "autodepositing" compositions, dispersions, emulsions, suspensions, baths, solutions, processes, methods, or a like term. Autodeposition is often contrasted with electrodeposition, which can produce very similar adherent films but requires that metal or other objects to be coated be connected to a source of direct current electricity for coating to occur. No such external electric current is used in autodeposition.

Autodeposition compositions previously known in the art are effective for coating many metals of practical interest, but it has been observed that attempting autodeposition coating of most zinc-rich metal surfaces such as galvanized steel often results in coatings with many small "pinholes" or larger blisters. Such coatings are usually regarded as aesthetically unpleasing and often fail to provide the protection against the environment that is normally wanted from autodeposition coatings. Reducing or eliminating the formation of pinholes or larger blemishes in autodeposited coatings, particularly on zinciferous surfaces, more particularly galvanized steel or some variation thereof, is a major object of this invention.

DESCRIPTION OF RELATED ART Autodeposition has been in commercial use on steel for about thirty years and is now well established for that use. For details, see for example, U. S. Patents 3,592,699 WO 97/09127 PCT/US96/13480 of July 13, 1971 to Steinbrecher et al.; 4,108,817 of Aug. 22, 1978 and 4,178,400 of Dec.

11, 1979, both to Lochel; 4,242,379 of December 30, 1980 and 4,243,704 of Jan. 6, 1981, both to Hall et al.; and 5,342,694 of Aug. 30, 1994 to Ahmed. (The disclosures of all of these immediately above noted U. S. Patents, except to the extent that they may be inconsistent with any explicit statement herein, are hereby incorporated herein by reference.) However, preparation of coatings free from flaws on more electrochemically active substrates such as zinc has continued to prove challenging, especially when using an often preferred chemical type of autodeposition resin, an internally stabilized crystalline copolymer ofvinylidene chloride.

DESCRIPTION OF THE INVENTION General Principles of Description Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word "about" is in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, unless expressly stated to the contrary: percent, "parts of', and ratio values are by weight; the term "polymer" includes "oligomer", "copolymer", "terpolymer", and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among the constituents of a mixture once mixed; specification of materials in ionic form implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole, and any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to the objects of the invention; and the term "mole" and its variations may be applied to ionic, chemically unstable neutral, or any other chemical species, whether actual or hypothetical, that is specified by the types of atoms present and the number of each type of atom included in the unit defined, as well as to substances with well defined neutral molecules.

Summary of the Invention It has now been found that contact of metal surfaces, particularly of galvanized steel or like zinciferous surfaces and of aluminum and its alloys that contain at least of aluminum, after any cleaning needed or desired but before autodeposition, with an s aqueous solution having a surface tension value at 30° C not greater than 55 dynes per centimeter and including water and: at least 0.008 based on the total solution, of a component of dissolved phosphonates, and, optionally, one or both of the following components: a component of dissolved surfactant, exclusive ofphosphonates; and a component of dissolved non-oxidizing mineral acid, exclusive of any material that is part of component or is exceptionally effective in reducing formation of pinholes or similar surface blemishes after subsequent autodeposition. For purposes of this description, a "non-oxidizing mineral acid" is defined as in column 2 line 50 56 of U. S. Patent 4,477,390 of Oct. 16,1984 to Ledent et al., the entire specification of which, except to the extent contrary to any explicit statement herein, is hereby incorporated herein by reference. Such metal pretreatment compositions constitute one embodiment of this invention. Another composition embodiment of the invention is a concentrate from which a working composition according to the invention can be prepared by dilution with water.

In its simplest embodiment, a process according to this invention comprises three steps: contacting a metal surfaced object with a blemish inhibiting aqueous liquid precoating composition as described above at a suitable temperature for a sufficient time to result in fewer blemishes in a subsequently autodeposited coating, this step being denoted briefly as "blemish inhibiting precoating treatment" or "BIPT" and the aqueous liquid 25 composition used being usually briefly denoted hereinafter as "BIPTC"; (ii) removing the metal surfaced object from contact with the BIPTC; and (iii) applying an autodeposited coating on the surface treated with the BIPTC in step Detailed Description of Preferred Embodiments The autodeposition composition and process themselves and treatments with oth- 30 er compositions before the BIPT and after autodeposition, for example, cleaning the substrate before contact with the BIPTC, simple and/or reactive rinses after autodeposition, the use of chromium containing or other known advantageous posttreatment composi- WO 97/09127 PCT/US96/13480 tions after autodeposition and rinsing, and heating or other processes such as steam treatment to stabilize the initially formed coating film, are generally the same in an extended process according to this invention as in the prior art. Specific preferred conditions are described in the working examples below.

Preferably, a process according to this invention also includes a rinse of the wet, although drained, uncured coating formed in the autodeposition bath with one of the aqueous compositions often known in the art as "reactive rinses", also known simply as "rinses". Particularly preferred reactive rinses are described in U. S. Patent 5,372,853 of Dec. 13, 1994 and in U. S. Application Serial No. 08/316,437 filed Sep. 30, 1994, which, except to the extent that they may be inconsistent with any explicit statement herein, are hereby incorporated herein by reference. Other suitable reaction rinses are described in the following U. S. Patents, the specifications of all of which, except to the extent that they may be inconsistent with any explicit statement herein, are hereby incorporated herein by reference: 5,432,694 of Aug. 30, 1994; 5,428,525 of Sep. 30, 1993; and 5,164,234 of Nov. 17, 1992.

Any cleaning of the zinciferous surfaced object that is known to be needed or desired before autodeposition coating in the prior autodeposition art may advantageously be, and preferably is, utilized in connection with this invention before the blemish inhibiting precoating treatment instead.

Under certain conditions, it may be advantageous to rinse with water a substrate surface treated with a BIPTC according to the invention before introducing the substrate into the autodeposition bath. Such rinsing is often unnecessary, however, and if not needed is preferably avoided for economy.

Characteristic component of a composition according to this invention preferably is selected from the group consisting of phosphonate ions that contain at least one amino nitrogen atom, preferably a tertiary amino nitrogen atom, per ion. Independently, the ions of this characteristic component are preferably selected from ioms that contain at least 2, or more preferably at least three, phosphonate moieties per ion. Also independently, when amino nitrogen is present, divalent hydrocarbon moieties selected from the group of methylene and polymethylene moieties preferably connect the phosphorus atoms in each phosphonate moiety with an amino nitrogen atom; most preferably, these connecting moieties are methylene, with oligomers of methylene increasingly less WO 97/09127 PCT/US96/13480 preferred as the number of carbon atoms in these oligomers increases.

For convenience and economy, the ions of component are preferably added to the BIPTC in the form of the commercially available corresponding phosphonic acids.

The single most preferred source for characteristic component is diethylene triaminepenta{methylene phosphonic acid} with the chemical formula:

H

2

PO

3

CH

2

N{(CH)N-(CH

2 POH2) 2 2 and the second most preferred is aminotri{methylene phosphonic acid} with the chemical formula: N-(CH 2

PO

3

H

2 3 The concentration of characteristic component in the BIPTC can generally vary over a wide range without affecting the effectiveness of blemish inhibition very strongly, particularly with the most effective inhibitors. For each particular molecular type in component there is expected to be a "threshold" value below which little or no inhibition will be achieved. In many cases, there is also expected to be a value, usually at least two orders of magnitude above the threshold value, above which the blemish inhibiting effectiveness of a particular molecular type decreases, perhaps because the acidity becomes too high. Therefore, the technically preferable values of concentration of component will depend in detail on the particular molecules used. In addition, the practically preferable value will depend on economics: If the rinse solution is not recycled, as is usually more convenient, it is preferable from the cost point of view to use as little of the inhibiting additive as will be adequately effective for the purpose.

Generally, from the viewpoint of obtaining maximum inhibition of blemishes, the concentration of component in a working precoat treatment composition according to the invention preferably is, with increasing preference in the order given, at least 0.0085, 0.0088, 0.0091, 0.0094, 0.0097, or 0.0100, and for less preferable molecular types more preferably is, with increasing preference in the order given, at least 0.020, 0.030, 0.040, or 0.080 Independently, for economic reasons, the concentration of component in a working precoat treatment composition according to the invention preferably is, with increasing preference in the order given, not more than 50, 25, 10, 3, 2, 1, 0.5, 0.3, 0.2, 0.10, 0.080, 0.060, or 0.050 and for the most preferred molecules for component more preferably is, with increasing preference in the order given, not more than 0.040, 0.020, or 0.015 The concentration of phosphonate was determined by titration of a 250 milliliter (hereinafter usually abbreviated sample of working composition with 0.025 N WO 97/09127 PCT/US96/13480 thorium nitrate solution, after acidification of the sample with a solution of 1 nitric acid in water to the extent necessary to make the sample clear and light yellow in color and then addition of 1 mL of a solution of 9.45 grams of monochloroacetic acid in a mixture of 40 mL of 5 NaOH solution in water and 60 mL of additional deionized water, using alizarin indicator, to the first salmon pink end point that persists for at least seconds. Each mL of the titrant solution consumed corresponds to 12.8 part per million of phosphonates in the working composition.

In general, the preferred phosphonic acid sources of component are commercially available only in solution in combination with non-oxidizing mineral acids that act to stabilize the acids against crystallization, as described in U. S. Patent 4,477,390 already cited above. Accordingly, compositions according to the invention normally preferably contain optional component The amount of component when it is made up of hydrochloric acid as is generally most preferred, preferably is such that the ratio of component to component the latter measured as its stoichiometric equivalent is of corresponding phosphonic acids, is at least, with increasing preference in the order given, 0.10. 0.15, 0.20, 0.25, 0.28, 0.30, or 0.32:1.0 and independently preferably is not more than, with increasing preference in the order given, 1.0:1.0, 0.80:1.0, 0.70:1.0, 0.65:1.0, 0.60:1.0, 0.55:1.0, 0.50:1.0, 0.45:1.0, 0.40:1.0, 0.37:1.0, 0.35:1.0, or 0.33:1.0.

In order to maximize the probability for avoiding blemishes, the surface tension of the precoat treatment composition according to this invention preferably is, with increasing preference in the order given, not more than 50, 48, 46, 44, 42, 41, 40, 39, 38, 37, 36, 35, or 34 dynes per centimeter when measured at 30 °C by the Whilmey slide (or plate) method. For details of the measurement of surface tension, see A. Adamson, Physical Chemistry of Surfaces, 3rd Ed., (John Wiley Sons, New York, 1976), p. 23 and C. Weser, "Measurement of Interfacial Tension and Surface Tension General Review for Practical Man", GITFachzeitschrift fur das Laboratorium, 24 (G-I-T Verlag Ernst Giebeler, Darmstadt, Germany, 1980), 642 648 and 734 742.

Component generally has a slight surface tension reducing effect on otherwise pure water, but in order to achieve more preferable values of surface tension for a working precoat treatment composition according to the invention, additional surfactant is generally preferred as a component of the BIPTC. Any surfactant that is chemically stable in combination with component and water, (ii) is effective in reducing the sur- WO 97/09127 PCT/US96/13480 face tension, and (iii) does not have any adverse effect on the quality of the coating subsequently formed by autodeposition may be used. One group of surfactants that have been found particularly suitable and are effective in economically small concentrations are aromatic sulfonates and their salts, particularly the disulfonated derivatives of dodecs yl diphenyl ether commercially supplied by Dow Chemical Co., Midland, Michigan under the names DOWFAX T M 2A1 and 2A0 Solution Surfactants. The preferred amounts of any surfactants are those required to attain the preferred surface tension values stated in detail herein. For DOWFAXr M 2A1, which is normally most preferred, the concentration in a working BIPTC preferably is, with increasing preference in the order given, at least 0.0003, 0.0006, 0.0009, 0.0012, 0.0015, 0.0018, 0.0021, 0.0024, 0.0027, 0.0030, 0.0032, or 0.0034 and, primarily for reasons of economy, independently preferably is, with increasing preference in the order given, not greater than 0.05, 0.03, 0.010, 0.0070, 0.0050, or 0.0040 The time of contact between the metal substrate being treated and the BIPTC according to this invention and the temperature during this contact may vary within wide limits. Generally, with the preferred treatment compositions, the contact time preferably is, with increasing preference in the order given, at least 5, 10, 15, 25, 35, 45, 50, 55, or seconds (hereinafter usually abbreviated "sec") and independently, primarily for reasons of economy, preferably is, with increasing preference in the order given, not more than 30, 15, 10, 5, 4, 3, 2, 1.7, 1.5, 1.3, or 1.1 minutes (hereinafter usually abbreviated The treatment compositions according to the invention generally are adequately effective at normal ambient temperatures of 20 25 C and for convenience and economy are generally preferably used within such a temperature range, although they may be used at any temperature between their freezing and boiling points.

The autodeposition bath used for a process according to this invention preferably comprises, more preferably consists essentially of, or still more preferably consists of water and: from 5 to 550, more preferably from 30 to 300, still more preferably from 40 to 120, and most preferably from 40 to 80, g/L of a stably dispersed organic coating resin; from about 0.4 to about 5, more preferably from 0.5 to 4.0, still more preferably from 1.0 to 3.0, g/L of fluoride ions;

I

an amount sufficient to provide from about 0.010 to about 0.20, more preferably from 0.011 to 0.09, still more preferably from 0.012 to 0.045, oxidizing equivalents per liter of an oxidizing agent selected from the group consisting of dichromate, hydrogen peroxide, ferric ions, and mixtures thereof; and S a source of hydrogen ions in an amount sufficient to impart to the autodeposition composition a pH in the range from 1.6 to 3.8, more preferably from 1.7 to still more preferably from 1.8 to One preferred type of coating resin for use in forming autodeposited coatings in a process according to the present invention comprises internally stabilized vinylidene chloride copolymers or externally stabilized vinylidene chloride copolymers containing in excess of 50 or more preferably at least 80 of residues from polymerizing vinylidene chloride. Most preferably, the vinylidene chloride copolymer is crystalline in nature. Exemplary crystalline resins are described in U.S. Patents 3,922,451 and 3,617, 368, the disclosures of which, except for any part that may be inconsistent with any exis plicit statement herein, are hereby incorporated herein by reference. Generally, crystalline poly(vinylidene chloride) containing resins comprise a relatively high proportion of residues from vinylidene chloride, for example, at least about 80 by weight thereof.

A second preferred type of resin for use in autodeposition coating in connection with this invention is an acrylic type, particularly copolymers of acrylonitrile. Further details are given in U. S. Patent 4,313,861 of Feb. 2, 1982 to Bassett et al., the disclosure S* ofwhich, except for any part that may be inconsistent with any explicit statement herein, is hereby incorporated herein by reference.

The working BIPTC's may be conveniently prepared on site where used by diluting concentrates with water, and such concentrates are also within the scope of this in- 25 vention. Concentrates normally preferably contain from 3 to 20 times the concentrations of components and as described above for working compositions.

The terms "comprise", "comprises", "comprised" and "comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or 30 components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

I 8 8a The practice of the invention, especially in its preferred embodiments, may be further appreciated from the following non-limiting examples and comparison examples.

Group 1 General Experimental Procedure The process sequence used for this group of examples is shown in Table 1-1 below. (Note: All products identified herein by the trade marks PARCO®,

RIDOLINE®,

e 22* WO 97/09127 PCT/US96/13480 Table 1-1 PROCESSING STEPS USED, GROUP 1 Process Step Fluid Used Fluid Temper- Contact ature, OC Time, Min Spray Preclean 72 g/L ofPCL 1530A' 49 Dip Clean 144 g/L of PCL 1530A' in 60 water Dip Rinse 10 g/L ofPCL 1530A 2 in 20 25 water Dip BIPTC See Table 2 20 25 Dip Rinse DI water 20 25 Dip Autodeposition 6 7 solids; see detailed 20 25 See Note 3 composition elsewhere Dwell Ambient air 20 25 0.25 Dip Rinse Solution made by mixing 49.6 20 25 1 parts of CoCO 3 330.3 parts of a solution in water of 20 fluozirconic acid and 2.1% HF, and 638.5 parts of DI water 4 Cure Hot air 88 General Notes for Table 1-1 "PCL" is an abbreviation for "PARCO® Cleaner". PCL 1530A, with or without added PCL 1530S (see footnote 1 below), is a conventional moderately strong alkaline cleaner with surfactants.

Footnotes for Table 1-1 'If substrates were not free from water breaks when using PARCO® Cleaner 1530A alone, 2 g/L of PARCO® Cleaner 1530S were also dissolved in the spray precleaning and dip cleaning fluids.

2 No PCL 1530A or S was deliberately added to this fluid, but because of drag-out from the preceding stage, it may have contained as much as 10 g/L.

3 The immersion time, along with the solids concentration of the autodepositing composition (within the 6 7 range specified), was adjusted to produce a dry autodeposited coating thickness of 17.8 2.5 micrometers.

4The solute in this solution is believed to consist predominantly of cobalt fluozirconate after mixing and evolution of gas, presumably carbon dioxide, which occurs after mixing. The solution was replaced after every 100 panels processed.

I

WO 97/09127 PCT/US96/13480 and AUTOPHORETIC®, together with detailed directions for using them as described below, are commercially available from the Parker Amchem Div. of Henkel Corp., Madison Heights, Michigan.) The precoat treatment bath compositions are shown in Table 1-2 below.

Preparation of 18.5 liters (hereinafter usually abbreviated of a "normal activation" autodeposition bath was accomplished as follows: Into an adequate size high density polyethylene (hereinafter usually abbreviated as HDPE") container for the final mixture were added 3.37 kilograms (hereinafter usually abbreviated of AUTO- PHORETIC® 866 Replenisher (hereinafter usually abbreviated "866 Replenisher" or simply which contains 37.5 solids, and 12.1 kg of industrially deionized (hereinafter usually abbreviated water. To this first mixture, a separately mixed solution of 0.99 kg of AUTOPHORETIC® Starter 300 (hereinafter usually abbreviated as "Starter 300" or "S 300") and 2.96 kg of DI water was then slowly added with constant stirring, using a motor driven stirrer. Addition of the starter solution to the solution of 866 took approximately 20 minutes. Sufficient hydrofluoric acid was then added to result in a reading of 248 microamperes (hereinafter usually abbreviated on a LINE- GUARD® 101 fluoride activity meter (hereinafter usually abbreviated "101 Meter").

This composition had an oxidation-reduction potential (hereinafter usually abbreviated "ORP") value for a smooth platinum electrode immersed in the composition, compared to a standard hydrogen electrode, of375±25 millivolts (hereinafter usually abbreviated "mv") Preparation of a "low activation" autodeposition bath was performed identically to the "normal activation" bath, except for using the following amounts of materials: 3.37 kg of 866 Replenisher with 9.24 kg of DI water; 0.70 kg of Starter 300 diluted with 3.12 kg ofDI water; and a reading of 110 /A on the 101 Meter. The ORP was the same as for the "normal activation" bath. The coating resin in both these examples of autodeposition baths is a crystalline copolymer ofvinylidene chloride.

During use, autodeposition baths were maintained between 6 7 of total solids by the addition of 866 Replenisher as needed to compensate for the loss of coating resin from the baths, primarily by transfer of the resin into the autodeposited coatings formed during use. AUTOPHORETIC® Oxidizer 24 was added to maintain the ORP range specified above for each bath, and hydrofluoric acid was added to maintain 101 Meter WO 97/09127 WO 9709127PCT/US96/13480 Table 1-2 PRECOAT TREATMENT BATH COMPOSITIONS, GROUP 1 PRECOAT ACTIVE INGREDIENT DESIGNATION INGREDIENT(S) CONCENTRATION D2060 A DequeStTM 2060 0. 01 Active DoWfaXTm 2A 1 0.0031 Wt*Vol Active D2060 B DeguestTm 2060 0.02 Active DowfaXTm 2A 1 0.0031 Wt-Vol Active D2060 C DeguestTm 2060 0.04 Active DowfaXTm 2A 1 0.0031 Wt*Vol Active D2000 A DequestTm 2000 0. 01 Active DoWfaXTm 2A 1 0.0031 Wt*Vol Active D2000 B DeguestTm 2000 0.02 Active DoWfaXTm 2A 1 0.0031 Wt-Vol Active D2000 C DegueSt Tm 2000 0. 04 Active DowfaxTm 2A 1 0.0031 Wt*Vol Active D2060/2A0 DegUeStTm 2060 0. 04 Active DoWfaXTm 2A0 0.0031 Wt-Vol Active

H

3 P0 4 A H 3 P0 4 0.20 Molar

H

3 P0 4 B H3PO 4 0.40 Molar HP0 4 C H 3 P0 4 0.80 Molar HF H 2 0 2 HF 0.0011 Active 2 0 2 1. 0 Active DI DI Water Notes for Table 1-2 Precoat Designation DI and all other Precoat Designations not beginning with the letter are comparison examples, not according to the invention.

"Wt*Vol %W means that the volume of the liquid solution in which the DOWFAXTm surfactants are supplied was measured directly; then the volume percent corresponding to this volume in respect to the volume of the entire composition was multiplied by the weight percent of phosphonic acid(s) in the liquid solution to obtain the "Wt*Vol WO 97/09127 PCT/US96/13480 readings of 250±25 tA in the "normal activation" (hereinafter usually abbreviated as autodeposition bath and 110 10 pA in the "low activation" (hereinafter usually abbreviated as bath. A separate BIPTC was used for each type NA or LA) of autodeposition bath.

All metal substrates processed were rectangular panels 10.16 x 15.24 centimeters (hereinafter usually abbreviated in size; these were prepared by bisecting rectangular panels 10.16 x 30.48 cm in size supplied by ACT Laboratories, Inc., Hillsdale, Michigan. Three types of metal were used: Cold Rolled Steel (hereinafter usually abbreviated Code APR 11721, 6.6 millimeters (hereinafter usually abbreviated thick, clean, unpolished, Batch 30425414 or 31021314; Hot-dipped Galvanized Steel (hereinafter usually abbreviated Code APR 10260, 8.9 mm thick; and Galvannealed Steel (hereinafter usually abbreviated Code APR 16966, 7.6 mm thick, clean, unpolished, Batch 20622416 or 20315416. Panels were dipped two at a time, using two hooks attached to the same supporting rod, for the process sequence. A total of 18 panels were processed for each BIPTC: six of CRS, six of G60 and six of Physical testing included GM 9511P, 20-cycle, scribe/scab, 504-hour salt spray (ASTM B 117-90), impact (ASTM 2794-87, except that no evaluation of the pattern of coating removed by the tape was made), and initial adhesion (ASTM D3359-87) testing.

Table 1-3 lists observations of the presence of pinholing/blistering on the initially oven cured coated panels as well as impact, GM 9511P, 20-cycle scribe/scab, salt spray and initial adhesion results. Coatings having significant blistering and/or pinholing after oven cure were not tested further.

The following conclusions were drawn from the results shown in Table 1-3: The experimental BIPTC's found to give the best overall performance were those containing DEQUEST r M 2060. Concentrations of at least 0.02 of this material (which contains only about 50 of its active phosphonic acid ingredient) appeared to give the best overall results under both low and normal activation conditions for the autodeposition bath. G60, A60 and CRS panels were all pinhole and blister-free after oven cure.

Initial adhesion was not affected by the precoat treatment step when compared to a DI comparison precoat treatment step, but corrosion results after subsequent autodeposition coating were substantially better with a treatment composition according to the invention.

Differences in salt spray and scribe/scab performance results between low and normal WO 97/09127 WO 9709127PCT/US96/13480 Table 1-3 STEEL AND ZINC-ALLOY STEEL COATING PROCESS RESULTS, GROUP 1 Precoat Bath/ Pinhol- Initial i- 504 Hir SS Scribe/ Desig- Panel ing/Blis- Adhe- pact Scab nation Types tering Sion Creep, Mm None 5B 69 0 4 13S, 0 3 D2060 A LA/A60 None >413 69 0-49s, 0-49s1, LAICRS None >4B3 115 0-12s, 1-2 2,2 None 51B 46 2-3 4S, 0-3'1 1, D2060 B LAIA60 None 513 46 0- 12XTF6, 0-I's1, LAICRS None >413 161 0-2, 0-2 4,3 None 5B3 23 1-26s, 1-21s, D2060 c LA/A60 None >413 69 0-12sVF8,0-3'"1, LA/CRS None >413 69 1-1, 1-12s 2,2 None SB 23 0-3's, 1 -36s 1,1 D2000 A LA/A60 None 11B <23 0- 2 s VF5,0-2 VF5 1,1 LA/CRS None >4B 184 1-1, 1-12s 3,3 None 5B 46 0-2&s F6, 0-28s F6 1,1 D2000 B LAIA60 None lB3 23 0-37S, 0-26s 1,1 LAICRS None >4B3 138 0_ I 2, 0_-1 2,2 None 51B 23 0-48s V176, 0 3 1's 1,1 D2000 c LA/A60 None >413 <46 0-2 3 SVF6,0-12sVF6 1,1 LA/CRS None >4B 138 1-1, 1-1 2,2

H

3 P0 4 LA/G60 Very Few 213 <23 0-3s VF6, 0 2 's 5%P 1,1 A Pinholes Medium Pinholes LA/CRS Very few >413 184 0 1 2S. 0_ 2,3 -blisters Table continued on next page..

13 WO 97/09127 PTU9/38 PCT/US96/13480 Precoat Bath/ Pinhol- initial Im-_ 504 Hr SS Scribe/ Desig- panel ing/Blis- Adhe- pact Scab nation Types tering sion Creep, Mm HIP0 4 LA/G60 Few 3-4B <23 0-23s FM4, 0-2"s 2,2 B pinholes ____FM6 LAIA6O Medium pinholes LAICRS Very few >4B3 184 0_1 _1S2,2 pinholes HIP0 4 LA/G60 Very few 3B3 <23 0-2 4S, 0-34s1, C blisters Medium pinholes LAICRS Very few >4B3 184 0_12S, 0_12 2,2 blisters HP LA/G60 None 51B <46 1-36s VF8, 0-2's VF6 1,1

H

2 0 2 LAIA6O Pinholes LA/CRS None >4B 184 1-1,0-1 2,2 DI LAIG60 None 51B 161 3-11 5%P,0-3sSF6 1,1 None 213 <23 0-35s VF6, 0_ I SF6 1,1 LA/CRS None >4B 184 1-1,1-1 1,2 Corn. A NA/CRS None SB3 <23 1-2, 1-2 F9 2,2, 2,2 Corn. B -None 51B <23 N, 0 -Is 3,3, 2,3 D2060 NA/G60 None >413 <23 O-3'os 5%P, 0~4's 1, <1

A

None >4B 46 0-26s F8, 0 2 4s F2 1 NAICRS None >413 46 1-2, 1-2 2, 2 D2060 NAJG6O None >4B <23 0-4 VF6, 0 3 4s 5%P <1 None >4B- <23 0- 2 s VF8, 0-2s VF8 <1 NA/CRS None >4B 46 1-1, 1-2 2,2 D2060 NAJG6O None >413 <23 0 2 4S VF8, 0-48s VF6 I

C

None >413 <23 0 2 s VF8, 0-2s VF8 I NA/CRS None >413 23 1-1, 1-1 2,2 D2000 NA/G60 None >413 <23 0 3 9s VF4, 1-4 VF6 1,1

A

NAJA6O Very few 213 <23 0-2 F8, 0-2 3s F8 1,1 bisters NA/CRS None >413 <23 1 1-2, 1-2 3,2 *..Table continued on next page..

14 WO097/09127 PCTIUS96/13480 Precoat Bath/ Pinhol- Initial Im- 504 Hr SS Scribe/ Desig- Panel ing/Blis- Adhe- pact Scab nation Types tering Sion Mmn D2000 B NA/G60 None 513 <23 0-40sF6, I-3VF8 <1,1 NAIA6O Very few 213 <23 0-4' F8, 0-4s F6 1,1 blisters NA/CRS None >413 <46 1_12S, l_-lS 2,2 D2000 C NA/G60 None >413 <23 1-48sF6, 14'sF6 1,1 NAIA6O Few-Med. 413 <23 0-3s VF8, 0- Is VF8 <1 NAICRS None 513 69 1-2, 1-2 2,3 HIP0 4 A NA/G60 Very few l B <23 0-26s F6, 0-4s F6 1, 1 (VF9, pinholes VF9) Medium NA/CRS None >4B3 46 1m2S, l-l2S1, jHP0, B NA/G60 Very few 11B <23 0-3 F6, 0-36s F6 1, 1 WF,) NAIA6O Medium _pinholing_______ NAICRS None >4B 46 1-2, 1-2 2,3

H

3 P0 4 C NA./G60 Very few IlB <23 0-36s F 6 0-3 F, 1,1 VF,) Medium NAICRS None >4B3 46 1_1, 1_12S 4,2 I-IF+ NA/G60 Few- 3-4B3 <23 I-23s, 1-2 1,1 (FM8,

H

2 0 2 medium FM8) pinholes Medium pinholing blisters NAICRS None 5-B 46 1-2, 1 2 3S 2,2 DI NAIG60 Few 313 <23 1-3 6 s F6, 1-3 F4 1,1 NAIA6O Medium lB3 <23 pinholes few blisters >413____12_2, NA/CRS None 4B <69 Table continued on next page..

WO 97/09127 PCTIUS96/13480 Precoat Bath/ Pinhol- Initial Im- 504 Hr SS Scribe/ Desig- Panel ing/Blis- Adhe- pact Scab nation Types tering sion Creep, Mm D2060/ NA/G60 None >4B <23 0-36s, 0-2 1 0 <1,1 None >4B <23 0 -4s F8, 0-2 F8 1,1 NA/CRS None >4B >23 1-2, 1-1 2,2 Notes for Table 1-3 "Comp. A" is a comparison example in which no precoat treatment was used and the rinse after autodeposition was an aqueous solution of ammonium carbonate, but other process steps were the same as for "normal activation" autodeposition according to the invention.

"Comp. B" is a comparison example in which the metal substrate was coated with an electrodeposited paint (PowercronTM 500) that is generally considered very high in quality, instead of any autodeposited coating.

activation baths were not significant.

Coatings after DEQUEST T M 2000 containing pretreatment compositions had comparable salt spray and scribe/scab performance to those after DEQUESTr M 2060. However, DEQUESTTM 2000 containing precoat treatments were less effective at pinhole prevention over galvannealed A60 panels under "normal activation" bath conditions (101 Meter reading 250 and appeared to require at least twice as high a concentration as with DEQUESTrm 2060 containing compositions to provide the most corrosion resistance on the more difficult to protect galvannealed substrates.

H

3 P0 4 containing conditioning rinses were unable to produce pinhole-free coatings over galvannealed A60 steel at all precoat concentrations and ACC-866 bath activation levels tested. Salt spray and scribe/scab performance results were slightly lower than for the DEQUESTrT aminophosphonic acid containing BIPTC's.

HF H 2 0 2 mixtures were not effective in eliminating pinholes and blisters on galvannealed steel.

Salt spray (ASTM B 117-90) tests resulted in some field blistering and cathodic delamination spots on both G60 and A60 panels for all precoat conditioning rinses tried here. Such results are always or almost always observed during this type of testing of samples with zinciferous surfaces, even when these surfaces are protected with coatings known to give excellent corrosion resistance under practical use conditions. However, the precoat conditioning rinses do appear to reduce the severity of the salt spray induced field blistering and delamination, which are much less severe for A60 panels than for G60 pan- WO 97/09127 PCT/US96/13480 els in general.

GM 9511P, 20-cycle scribe/scab data were excellent for all DEQUESTM aminophosphonic acid containing BIPTC's and both ACC-866 bath activation levels tried. Typical creep widths for all A60 and G60 panels were 1 mm or less in total creep. Total creep s widths over CRS were typically 2 mm, comparable to those now achieved with the best prior art autodeposition technology, indicating that autodeposition coatings applied after a BIPT according to the invention are at least as satisfactory as other autodeposition coatings on CRS and therefore may be used on composite objects containing both CRS and zinc coated surfaces without deterioration of the best performance now achieved by autodeposition coating of CRS alone.

Impact test results were somewhat erratic as is normal for autodeposition coated CRS substrates, but there is no evidence that the aminophosphonic acid containing BIPT significantly affects impact test performance either adversely or positively.

Group 2 is A major objective of this group of examples was to establish consumption levels of the BIPTC active ingredients during prolonged use. Unless otherwise stated below, operating conditions were the same as for Group 1.

General Conditions of Operation In preparing the autodeposition baths, 0.94 rather than 0.99 kg of AUTOPHORET- IC® Starter 300 and 2.45 kg instead of 2.96 kg of water were used. The 101 Meter fluoride sensing reading was 150 instead of 240 gamps.

A BIPTC concentrate was prepared as follows: In an adequate size HDPE jug were mixed 54.00±0.01 g ofDequest 2060, 4.41±0.01 g ofDowfax 2A1 and sufficient DI water to produce a total concentrate mass of 3000±1 g. To prepare a working BIPTC, 150.0±0.1 g of the aforementioned BIPTC concentrate was then diluted to 3000± 1 g with DI water and stirred. 1300±1 g of this solution was added to a narrow stainless steel panel coating tank designed to accommodate the rectangular test panels, which were by 30 cm in size, with minimal solution volume.

Phosphonate concentrations in the working BIPTC's were monitored and maintained at intervals after use of the BIPTC by removing a 250±1 g sample of the BIPTC (while no substrates were being processed) and titrating this sample with a thorium nitrate solution as already described above. The remaining 1050±1 g of the used working WO 97/09127 PCT/US96/13480 BIPTC was then mixed with an amount of the BIPTC concentrate described above that was calculated, based on the results of the titrated sample, to result in a mixture having the original phosphonate concentration of the working BIPTC in a total mass of 1550± 1 g of the mixture, and sufficient DI water to bring the total mass of this mixture to 1550± 1 g was then added and well mixed. A second 250± 1 g sample was then taken from this mixture and titrated as described above, to determine whether the concentration of phosphonate in the mixture had been restored to at least the value originally present in the freshly made BIPTC. If it had, the remaining 1300+1 g of the mixture was usually continued in use as replenished used BIPTC to pretreat more substrate panels, as noted in specific instances below.

The general process sequence used for this group is shown in Table 2-1 below.

The substrate materials used, with the abbreviations for them used in the following description shown within quotation marks in parenthesis after each substrate type name below, were as follows: Cold Rolled Steel Code APR 11721, 6.6 mm thick, clean, unpolished, Batch 31216414.

Hot-dipped Galvanized Code APR 10260, 8.9 mm thick, clean, unpolished, Batch 20109516.

Galvannealed Code APR 16966, 7.6 mm thick, clean, unpolished, Batch 31004416.

Hot-dipped Galvanized/Cold Rolled Steel, Bimetallic, end-to-end lap joint Code 10270, Batch 21214416, Panel A: ACTCRS, Panel B: ACT Galvannealed/Cold Rolled Steel, Bimetallic, end-to-end lap joint ("A60/CRS"), Code 10270, Batch 21214416, Panel A: ACTCRS, Panel B: ACT Cured coating appearance data as a function of substrate and use or non-use of the acid cleaning and subsequent rinse steps are shown in Table 2-2 below. "Comparison I" in this table was a commercial product, AUTOPHORETIC® Conditioning Rinse 3180.

Panels in this processing sequence were processed one at a time, with the substrates being processed in the following sequence: First, six each of G60/CRS and CRS type panels were processed in alternating sequence. Secondly, nine CRS, nine and nine G60 panels were processed, one of each type being processed before a second one of any type was processed, etc. Thirdly, six G60/CRS and six A60/CRS panels were WO 97/09127 PCT/US96/13480 Table 2-1 PROCESSING STEPS USED IN GROUP 2 Process Step Fluid Used Fluid Temper- Contact ature, °C Time, Min Spray Alkaline Clean 60 g/L of RDL 1007 77 Dip Rinse Tap water 20 25 Dip Acid Clean' 2 by volume of AC 7150 66 Dip Rinse' Tap water 20 25 Dip BIPTC See Table 2-2 20 25 Dip Rinse DI water 20 25 Dip Autodeposition 6 7 solids; see detailed 20 25 See Note 2 composition elsewhere Dip Rinse Tap water 20 25 Dip Rinse Solution made by mixing 49.6 20 25 parts of CoCO,, 330.3 parts of a solution in water of 20 fluozirconic acid and 2.1 HF, and 638.5 parts of DI water 3 Cure Hot air 110 General Notes for Table 2-1 "RDL" is an abbreviation for "RIDOLINE® Cleaner"; RDL 1007 is a solid, powdered, titanated strongly alkaline cleaner concentrate. "AC 7150" is an abbreviation for AUTOPHORETIC® 7150 Acid Cleaner, a liquid concentrate for preparing a spray cleaning solution designed to remove light rust and oxidation from oil- and grease-free iron and steel surfaces before applying an autodeposition coating.

Footnotes for Table 2-1 'This step was used only on substrates that included some cold rolled steel, and not on all such substrates; exceptions are noted in the following tables.

2 The immersion time, along with the solids concentration of the autodepositing composition (within the 6 7 range specified), was adjusted to produce a dry autodeposited coating thickness of 25.4 2.5 micrometers.

3 The solute in this solution is believed to consist predominantly of cobalt fluozirconate after mixing and evolution of gas, presumably carbon dioxide, which occurs after mixing.

WO 97/09127 PCT/US96/13480 TABLE 2-2 Sub- Precoating Rinsing Composition: strate Type According to the Invention Comparison I DI Water With Acid Clean No Acid Clean CRS No blistering and/or No blistering and/or Blistering and/or Blistering and/or pinholing pinholing pinholing pinholing No blistering and/or No blistering and/or Trace of pinholing Slight to moderate pinholing pinholing blistering at edges Trace pinholing, trace Trace pinholing, trace Severe pinholing Severe pinholing blistering blistering and blistering and blistering Trace pinholing in spots Trace pinholing in spots Coating missing in Coating missing in CRS at joint interface. Coating at joint interface. spots near joint spots near joint missing in spots near joint interface. Blistering interface interface. and pinholing at lap joint and welds.

Coating missing in spots Trace blistering along Dense to severe CRS near joint interface. Trace joint interface edges. blistering on pinholing on A60 panel Trace pinholing on A60 panel half.

half. panel half. Blistering at interface joint.

again processed in alternating sequence. Fourthly, another eleven each of CRS, A60, and panels were processed in the same sequence as before, followed by three each of and A60/CRS panels in alternation with each other. Finally, various control and other test panels were processed as needed.

Table 2-3 shows data relevant to the consumption of phosphonate during a process according to the invention. The average consumption calculated from the values in Table 2-3 is 7.6 g of the BITC concentrate per square meter of substrate surface processed.

The working BIPTC was analyzed for various elements at the beginning and end of use as described above. Results are shown in Table 2-4. They indicate that zinc is the primary metal dissolved from the substrates during BIPT of galvanized steel according to the invention and that the phosphonate active ingredient is converted to some other soluble phosphorus containing compound, at least part of which remains in solution in the

BIPTC.

Physical testing results for Group 2 are shown in Tables 2-5, 2-6, and 2-7 below.

WO 97/09127 PCT/US96/13480 TABLE 2-3 Square Titration Observations and Responsive Actions Meters of Endpoint, Substrate mL of 0.025 Processed NThorium per Liter of Nitrate BIPTC Solution 0 10.2 Titration value for freshly made unused working BIPTC 1.19 6.5 Pinholing increase observed on A60 panel coated.

Added BIPTC concentrate to bring to 10.3 ml titration endpoint for the working composition, and continued processing.

3.09 Observed coating washoff in areas on G60 panel during tap water rinse after autodeposition step.

Added 130 mL of previously unused working BIPTC and continued processing.

3.38 5.3 Observed autodeposited coating washoff in areas during tap water rinse step.

Adjusted concentration with BIPTC concentrate to 10.6 ml titration value for the working composition and continued processing.

5.46 3.8 Autodeposited coating washoff in areas observed on panel.

Adjusted concentration with BIPTC concentrate to 11.7 ml titration value for the working composition. Continued until a total of 5.85 square meters per liter had been processed.

The results of Group 2 led to the following conclusions: The D2060/2A1 type BIPTC gave superior coating panel appearance compared to the best previous commercial BIPTC, AUTOPHORETIC® 3180 Conditioning Rinse.

Treatment according to the invention described herein gave coatings with no blistering and/or pinholing over CRS and G60 substrate, and only trace pinholing over A60 galvannealed steel was observed.

Elimination of the 7150 acid cleaning step improves coating coverage over a zinc coated steel-to-steel lap joint region with the best example of a BIPT according to the invention.

The initial consumption rate of active ingredient from the BIPTC was calculated to be 39.8 g of phosphonate per 1000 m 2 of substrate processed. Consumption rate diminished to approximately 23.7 g ofphosphonate per 1000 m 2 between 3.4 and 5.5 m 2 of WO 97/09127 WO 9799127PCTIUS96/13480 TABLE 2-4 Element Concentration of Element in the BLEPTC Analyzed For Before Use After Processing 5.85 m 2

IL

Fe <lIppm 4 ppm Zn Ippm 0.16% Si Ippm 4 ppm Al <lIppm <lIppm P 0.013% 0.12% Abbreviations for Table 2-4 "1ppm" "parts per million"; "m 2 square meters of substrate per liter of BIEPTC.

TABLE Substrate M 2 Initial Adhesion Values Impact Test Values Previously Treated' Zn Coated CRS Lap Joint Zn Coated CRS Portion Portion Interface Portion Portion 0.24 >4B >4B 4B >40 >160 1.34 >4B >140 1.90 >4B >120 2.37 >4B >4B >4B 120 >160 3.80 >4B 4.51 >4B >4B 4B >120 >160 5.24 4B >120 2 5.71 3-4B 4B 3-4B >80 >160 0.29 >4B >4B 4B >80 >160 1.38 >4B >140 1.81 >4B 120 Table continued on next page..

22 WO 97/09127 WO 9709127PCT/US96/13480 Substrate M 2 JL Initial Adhesion Values Impact Test Values Previously Treated' Zn Coated CRS Lap Joint Zn Coated CRS Portion Portion Interface Portion Portion 2.43 >4B3 >4B >4B3 >120 >160 3.85 >4B3 >100 4.56 >413 >4B 2B >120 >160 2 4.66 >413 >4B 4B >100 >160 2 5.27 4B G6OICRS >4B >413 4B >100 >160 4B -4 4B >4B 3-4B >80 >160 CRS 1.28 >4B >160 CRS 1.85 >4B >160 CRS 3.75 >413 >160

CRS

2 5.19 4B CRS -3 4B >160 CRS -4 >4B >160 CRS -5 >4B >160 CRS >4B <2 Footnotes for Table 'With the same batch of BLPTC, except for replenishment 2 The acid cleaning step and immediately following rinse step were omitted for this substrate in this instance. 3 Comparison example with AUTOPHORETICO Conditioning Rinse 3180 rather than a BIPT according to this invention. 4 Comparison example with no BIPT other than rinsing with DI water. 'Comparison example with no BIPT and with a different reactive rinse, AUTOPHORETICO Reaction Rinse 2150.

6 Comparison example with electrophoretic paint coating rather than autodeposited coating.

substrate processed per liter of starting BJPTC. This may be due to build up of soluble metal phosphonate byproducts in the used BLPTC.

A minimum concentration of about 83 ppm of phosphonate in the BIPTC is necessary for cured coatings to have the best appearance obtained. The nature of the failure or defects depended on the amount of substrate processed through the precoat bath. Lower WO 97/09127 WO 9709127PCT/US96/13480 2-6 Substrate M 2 /L Previously Scribe-Scab Test Result, mm Treated' Coated Portion CRS Portion 0.14

F-M

9 3, Field rust 0.33

F-

9 2, Field rust 0.76 1.05

F-M'

2.09 1, F-NI 9 2, Field rust 2.28 1, F-M 9 2, Field rust 2.62 1, F-M' 2.92 1, F-M 9 3.68

F-M'

3.94 1,1 F-M 6 4.34 F-M' 2, Field rust 4.43 1, F-Mg 2, Field rust 4.61 1, F-M 9 2, Field rust 0.19

F-M

9 2, Field rust G6OICRS 0.58

F-N

9 2, Field rust 0.81 1, F-M' 1.10 1, F-M? 2.14 F-M' 2, Field rust G6OICRS 2.33 F-M' 2, Field rust 2.67

F-M'

2.96

F-M'

3.58 1, F-M 4 3.99

F-M

6 2, Field rust G6OICRS 4.29

F-N

9 1 2, Field rust .Table continued on next page..

24 WO 97/09127 PCT/US96/13480 Substrate M 2 /L Previously Scribe-Scab Test Result, mm Treated' Zn Coated Portion CRS Portion 4.39 F-M 9 2, Field rust 4.70 F-M 9 2, Field rust 4.75 F-M 9 2, Field rust _3 F-M 9 2, Field rust

F-M

9 2, Field rust _4 F-M 4 -4 1, F-M 4 CRS 0.71 2, Field rust CRS 1.00 2, Field rust CRS 2.57 2, Field rust CRS 2.87 2, Field rust CRS 3.63 2, Field rust CRS 3.90 2, Field rust CRS -3 2 CRS -3 2 CRS _4 2, Field rust CRS 4 2, Field rust CRS _s 3,4,3,3 6 Field rust CRS 7 1,1,1,16 Footnotes for Table 2-6 1 With the same batch of BIPTC, except for replenishment. 2 The acid cleaning step and immediately following rinse step were omitted for this substrate in this instance. 3 Comparison example with AUTOPHORETIC® Conditioning Rinse 3180 rather than a BIPT according to this invention. 4 Comparison example with no BIPT other than rinsing with DI water. 5 Comparison example with no BIPT and with a different reactive rinse, AUTOPHORETIC® Reaction Rinse 2150.

6 Individual results from four replicate samples. 7 Comparison example with electrophoretic paint coating rather than autodeposited coating.

concentrations of phosphonate appeared to be adequate to produce cured coating with good appearance as phosphorus containing byproducts built up in the BIPTC.

WO 97/09127 WO 9709127PCTIUS96/13480 TABLE 2-7 Substrate M 2 JL Previously Rating after 504 Hours of Salt Spray Treated' Zn Coated Portion, Field CRS Portion, Field 0.43 0 FV, 7 o-12S 7 0.52 0 2 3s,6 0 _12S 7 0.90 0 2 s, FM', 8 1.19 0 4 s, 8 1.47 0 _13S 1.61 0 I2S PM', 1.99 0 7 0-1, 7 2.19 0_ I2S, FM 9 7 0-1, 7 2.74 0_ 1 3 S 7 3.04 0_ 13s, 3.33 0 4 s, F 2 8 4.04 0 1 3s, 7 0-1, 7 4.24 0 3 FM', 5 0-1, 7 5.81 0-1, 7 0 _12S 7 2 4.95 0-2, MD', 6 5.10 0 2 s, FM 6 8 2 5.76 0-1, 7 0 2S 7 G6OICRS 0.48 0-3 6S, D9, 5 0 _14S 7 G6OICRS 0.67 0 3 4S, VF 6 5 0-1, 6 0.96 0-2, D9, 7 1.23 0_ 2S ,D 9 7 1.52 0-2, D9, 1.66 0-2, MD 9 6 2.05 0-3, FM', 5 0 1 2s, 7 G6OICRS 2.23 0 3 s, FM', 5 7 Table continued on next page.

26 WO 97/09127 PCT/US96/13480 Substrate M 2 IL Previously Rating after 504 Hours of Salt Spray Treated'___ Zn Coated Portion, Field CRS Portion, Field- 2.82 0_12S, 7 3.38 0 3 6 ,4D MV 3.85 0-1, D 6 7 4.09 0-2, MDV, 5 0-1, 7 4.19 0-3, MV,5 0-1,7 2 5.00 0-2, 6 G602 5.14 0-3's, D 9 3

MV

8 6 G603 0 3 4S MD 8 5 G604 0_14S 7 G604 0 7 CRS 0.85 7 CRS 1.14 _0-1,7 1.57 0 1 7 CRS 1.72 VF8, 7 CRS 2.72 7 2.99 0-1, VV 8 7 3.14 0-1,7 CRS 3.28 7 CRS 3.48 1, VV 8 7 CR55.05 7 3 7

CRS

3 -0-1,7 4 0-1, 7 4 0-1,7 Table continued on next page..

27 M M WO 97/09127 PCT/US96/13480 Substrate M2/L Previously Rating after 504 Hours of Salt Spray Treated' Zn Coated Portion, Field CRS Portion, Field

CRS

5 0-1, VF 6 7

CRS

5 0-1 7

CRS

5 1-1, VF,_ 7

CRS

5 0-1, 7

CRS

6 0-1 s 9

CRS

6 7

CRS

6 0-1s 9

CRS

6 0- 1 s 9 Footnotes for Table 2-7 'With the same batch of BIPTC, except for replenishment. 2 The acid cleaning step and immediately following rinse step were omitted for this substrate in this instance. 'Comparison example with AUTOPHORETIC® Conditioning Rinse 3180 rather than a BIPT according to this invention. 4 Comparison example with no BIPT other than rinsing with DI water. 5 Comparison example with no BIPT and with a different reactive rinse, AUTOPHORETIC® Reaction Rinse 2150.

6 Comparison example with electrophoretic paint coating rather than autodeposited coating.

Initial adhesion and impact coating test results for coatings over G60 and substrates were unaffected by the amount of substrate processed in the best BIPTC according to the invention, until at least about 3.7 m 2 /L of original BIPTC had been processed. Continued use of replenished used BIPTC after that extent of processing resulted in somewhat lower adhesion and impact test values. Coating performance for coatings over a CRS substrate did not diminish with continued use of replenished used BIPTC.

Salt spray tests resulted in some field blistering and cathodic delamination spots for coatings after treatment according to the invention on both G60 and A60 substrates.

Variable field blistering was also observed but blister size and/or frequency had no consistent trend. All of these results are normal for almost any organic coating over zinc-rich metal surfaces, even for coatings known to give good practical performance. Ratings showed variability with no apparent trend as the area of substrate processed was increased. Coating performance was slightly better for coatings over the A60 substrate than the G60. Salt spray results over CRS were typically 0-1, comparable to all the types of is comparison examples tested, indicating that BIPT according to the invention is not detri- WO 97/09127 PCT/US96/13480 mental to the quality of autodeposited coatings over CRS, which already give fully satisfactory coating performance.

Scribe/scab test results were excellent for coatings after BIPT according to the invention over G60 and A60 substrates: Typical total creep widths for all A60 and panels were 1 mm or less. Typical creep widths over CRS were 2 mm, closely comparable to those achieved with currently preferred commercial autodeposition coatings from the same autodeposition compositions as used here.

Claims (21)

1. A process for forming a protective coating on a solid metallic surface, said process comprising steps of: contacting the solid metallic surface with an aqueous liquid blemish inhibiting precoating treatment composition ("BIPTC") having a surface tension value at 30°C not greater than about dynes per centimeter and comprising water and at least about 0.008% of dissolved phosphonate anions; (II) removing the solid metallic surface from contact with the BIPTC contacted in step and subsequently (III) autodepositing an organic protective coating on the solid metallic surface from step (II) by contacting the surface with an autodeposition bath.

2. A process according to claim 1, wherein the BIPTC additionally comprises at least about 0.0003% of a second surfactant in addition to phosphonate anions and has a surface tension not more than about 46 dynes per centimeter.

3. A process according to claim 2, wherein the BIPTC comprises at least about 0.0009% of surfactant molecules selected from the group consisting of aromatic sulfonates and their salts.

4. A process according to claim 3, wherein the surface tension of the BIPTC is not more than about 40 dynes per centimeter. p.

5. A process according to claim 4, wherein the BIPTC contains from 0.0021% to 0.010% of surfactant molecules selected from the group consisting o of dodecyl diphenyl oxide disulfonic acids and their salts. o V k

6. A process according to claim 5, wherein the dissolved phosphate anions are ions of diethylene triamine penta {methylene phosphonic acid}.

7. A process according to claim 4, wherein the dissolved phosphate anions are selected from the group consisting of ions of diethylene triamine penta {methylene phosphonic acid} and ions of aminotri {methylene phosphonic acid}.

8. A process according to claim 3, wherein the dissolved phosphate anions are selected from the group consisting of ions that contain at least one tertiary amino nitrogen atom and at least three phosphonate moieties per ion and contain divalent hydro-carbon moieties selected from the group consisting of methylene and polymethylene moieties connecting each phosphorus atom in a phosphonate moiety in the ion to an amino nitrogen atom in the ion.

9. A process according to claim 2, wherein the dissolved phosphate anions are selected from the group consisting of ions that contain at least two phosphonate moieties per ion and in which, if the ions contain an amino nitrogen atom, this atom is bonded to a divalent hydrocarbon moiety that is also bonded to a phosphorus atom in a phosphonate moiety.

10. A process according to claim 1, wherein the dissolved phosphate anions are selected from the group consisting of ions that contain at least two phosphonate moieties per ion. :o

11. An aqueous liquid composition which either as such or after dilution with additional water is suitable as a blemish inhibiting precoating treatment composition ("BIPTC") before autodeposition, said aqueous liquid composition having a surface tension value at 30°C not greater than about 55 dynes per centimeter and including water and: at least 0.008%, based on the total composition, of a component of dissolved phosphonate anions.

12. An aqueous liquid composition according to claim 11 including one or both of the following components: a component of dissolved surfactant, exclusive of phosphonates and their counter-ions; and a component of dissolved non-oxidizing mineral acid, exclusive of any material that is part of component or

13. An aqueous liquid composition according to claim 11 or 12, wherein said composition includes component to an extent of at least about 0.0003% and has a surface tension not more than about 46 dynes per centimeter.

14. An aqueous liquid composition according to claim 13, wherein said composition includes at least about 0.0009% of surfactant molecules selected from the group consisting of aromatic sulfonates and their salts.

An aqueous liquid composition according to claim 14 having a surface tension that is not more than about 40 dynes per centimeter.

16. An aqueous liquid composition according to claim 15 including from about 0.0021 to about 0.010% of surfactant molecules selected from the group consisting of dodecyl diphenyl oxide disulfonic acids and their salts.

17. An aqueous liquid composition according to claim 16, wherein the ions of component are ions of diethylene triamine penta {methylene phosphonic acid}.

18. An aqueous liquid composition according to claim 15, wherein the ions of component are selected from the group consisting of ions of diethylene triamine penta {methylene phosphonic acid} and ions of aminotri {methylene phosphonic acid}. 33

19. An aqueous liquid composition according to claim 14, wherein the ions of component are selected from the group consisting of ions that contain at least one tertiary amino nitrogen atom and at least three phosphonate moieties per ion and contain divalent hydrocarbon moieties selected from the group consisting of methylene and polymethylene moieties connecting each phosphorus atom in a phosphonate moiety in the ion to an amino nitrogen atom in the ion.

An aqueous liquid composition according to claim 13, wherein the ions of component are selected from the group consisting of ions that contain at least two phosphonate moieties per ion and in which, if the ions contain an amino nitrogen atom, this atom is bonded to a divalent hydrocarbon moiety that is also bonded to a phosphorus atom in a phosphonate moiety.

21. An aqueous liquid composition according to claim 11 or 12, wherein the ions of component are selected from the group consisting of ions that contain at least two phosphonate moieties per ion. .DATED this 26th day of July 1999 i HENKEL CORPORATION WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 SAUSTRALIA 00 290 BURWOOD ROAD 0 ocv