Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/78—Pretreatment of the material to be coated

Definitions

• This invention relates generally to coating compositions, in particular, coating compositions that can be applied to metal substrates to enhance paint adhesion even after extended coating times.
• the invention also relates to the coatings obtained from the coating composition, methods of applying these coatings and the coated substrate.
• a pretreatment coating is often applied to metal substrates, especially metal substrates that contain iron such as steel, prior to the application of a protective or decorative coating.
• the pretreatment coating minimizes the amount of corrosion to the metal substrate.
• the pretreatment coating can affect the adhesion of subsequently applied decorative coatings such as paints and clear coats.
• Many of the present pretreatment coating compositions are based on metal phosphates, and/or rely on a chrome-containing rinse.
• the metal phosphates and chrome rinse solutions produce waste streams that are detrimental to the environment. As a result, there is the ever-increasing cost associated with their disposal.
• these pretreatment coating compositions be effective in minimizing corrosion and enhancing decorative coating adhesion on a variety of metal substrates because many objects of commercial interest contain more than one type of metal substrate. For example, the automobile industry often relies on metal components that contain more than one type of metal substrate. The use of a coating composition effective for more than one metal substrate would provide a more streamlined manufacturing process.
• the coating compositions of the present invention are called pretreatment coatings because they are typically applied after the substrate has been cleaned and before the various primer and decorative coatings have been applied. In the automotive industry, coatings often comprise the following layers in order from the substrate out: a pretreatment coating for corrosion resistance, an electrodeposited electrocoat, then a primer layer, a base coat paint, and then a top clear coat. In the present application, all coatings after the pretreatment coating are considered as paints unless otherwise noted.
• Bonderite ® 958 available from Henkel Adhesive Technologies.
• Bonderite ® 958 provides a zinc-phosphate based conversion coating composition that includes zinc, nickel, manganese and phosphate.
• Bonderite ® 958 is a standard conversion coating used extensively in the automotive industry.
• the new class of coatings generally comprises a zirconium-based conversion coating deposited on a metal substrate by contact with a working bath containing dissolved zirconium in the coating compositions.
• These conversion coating compositions which are based on a zirconium coating technology, typically have no phosphates and no nickel or manganese. Zirconium-based coatings are finding increasing use in the automotive industry as a pretreatment coating.
• Manufacturing plants' metal coating assembly lines are part of an overall process that is highly coordinated and carefully timed. Metal workpieces are cut to size, formed, cleaned, coated with a pretreatment coating, and then coated with several over layers. Several different types of metal may pass separately through parts of the process to be joined to each other in one step and then proceed through the remaining process steps as an assembly of dissimilar metals. These processes are carried out on hundreds of pieces per hour and the system requires precise movement of a metal workpiece through the process. From time to time, the processing line may be halted, sometimes unexpectedly due to a problem in one of the processes in the assembly line. When line stoppage occurs, workpieces are held in the various stages of the line for far longer than is desirable.
• the coated workpiece does not perform up to required standards.
• the coated workpieces may not exhibit the desired corrosion resistance or paint adhesion characteristics. This can lead to increased scrap rates and potential recalls, which can drive up costs of manufacturing.
• zirconium-based conversion coating baths contain copper, either as an additive to improve features of the pretreatment coating and/or process or as a trace element from water or metal workpieces being coated. Regardless of its source, the present inventors have discovered that copper from the zirconium-based coating bath that is deposited in the pretreatment coating at too high an amount relative to other coating components can negatively affect performance of the coated metal substrate. Accordingly, it is desirable to develop zirconium-based coating baths that overcome this deficiency.
• this invention provides a metal pretreatment coating that is zirconium-based and that provides a longer pot life and enhanced paint adhesion without decreasing the corrosion resistance.
• the invention also relates to the coatings and coated substrate obtained from the coating composition.
• the zirconium-based metal pretreatment coating composition comprising water and dissolved Zr, a source of fluoride, a copper chelating agent, optionally materials comprising one or more of silicon, boron and yttrium and optional added dissolved Cu is provided.
• the zirconium-based metal pretreatment coating composition said copper chelating agent is capable of reducing amounts of copper deposited in a zirconium based coating on a metal substrate by contact with the zirconium based metal pretreatment coating composition, said copper chelating agent present in an amount sufficient to thereby produce an average total ratio of atomic % of Cu to atomic % of Zr in said coating deposited on the metal substrate that is equal to or less than 1.1.
• a zirconium-based metal pretreatment coating composition comprising:
• the added dissolved Cu is present in the coating composition and the copper chelating agent is present in an amount of 25 to 1500 ppm.
• the copper chelating agent is selected from molecules having multiple carboxylic and/or phosphonic functional groups.
• the copper chelating agent is selected from the group consisting of aminosalicylic acid, ascorbic acid, aspartic acid, benzoic acid, citric acid, cyanuric acid, diethylenetriamine-pentamethylene phosphonic acid, dihydroxybenzoic acid, dimethylenetriaminepentaacetic acid,
• ethylenediaminetetraacetic acid gluconic acid, glutamic acid, hydroxyacetic acid, hydroxy ethylidene diphosphonic acid, hydroxyglutamic acid, iminodisuccinic acid, kojic acid, lactic acid, malonic acid, nitrilotriacetic acid, nitrobenzenesulfonic acid, nitrosalicylic acid, oxalic acid, polyacrylic acid, polyaspartic acid, salicylic acid, tartaric acid, and salts of said acids.
• the zirconium-based metal pretreatment coating composition described above has a copper chelating agent comprising tartaric acid and/or salts thereof.
• Another aspect of the invention is a method for improving paint adhesion to a metal substrate comprising the steps of:
• the copper chelating agent is present in said zirconium-based metal pretreatment coating composition in an amount sufficient to result in an average total ratio of atomic % of Cu to atomic % of Zr in the pretreatment coating deposited on the metal substrate is equal to or less than 1.1 ; and c) applying a paint to the metal pretreatment coated metal substrate.
• Another aspect of the invention is a method for improving paint adhesion to a metal substrate that is subjected to a pretreatment with a zirconium-based pretreatment coating composition comprising the steps of:
• a zirconium-based metal pretreatment coating composition comprising dissolved Zr, a source of fluoride, optionally materials comprising one or more of silicon, boron and yttrium and optional added dissolved Cu, thereby forming a pretreatment coating on the metal substrate;
• the copper chelating agent is present in the pre-rinse in an amount sufficient to control the amount of copper deposited onto the metal substrate by the zirconium-based pretreatment coating composition such that the average total ratio of atomic % of Cu to atomic % of Zr in the pretreatment coating deposited on the metal substrate is equal to or less than 1.1.
• the copper chelating agent is present in an amount of at least 10 ppm and at most 2000 ppm.
• Another aspect of the invention is an article of manufacture comprising a coated metal substrate comprising: a metal substrate; and deposited on said metal substrate, a pretreatment coating comprising metal from said substrate, zirconium, oxygen, copper, and optional elements fluorine and carbon; wherein the pretreatment coating on the metal substrate has an average total ratio of atomic % of Cu to atomic % of Zr that is equal to or less than 1.1.
• the article of manufacture is provided wherein average total ratio of atomic % of Cu to atomic % of Zr in the pretreatment coating on the metal substrate is about 0.9 to 0.02.
• the article of manufacture is provided wherein atomic % of Cu in said pretreatment coating measured at a series of depths from an outer surface of the pretreatment coating to the metal substrate does not exceed 33 atomic % Cu at any of said depths.
• the article of manufacture is provided further comprising at least one paint applied to the pretreatment coating resulting in a painted coated substrate that achieves at least 95% paint remaining when tested according to ASTM 3330M (Revised Oct. 1, 2004).
• the article of manufacture is provided further comprising at least one paint applied to the pretreatment coating resulting in a painted coated substrate that achieves 1.9 mm or less average corrosion creep when tested according to ASTM Bl 17 (Revised Dec. 15, 2007) for 500 hours.
• the invention is directed to an aqueous metal pretreatment coating composition
• an aqueous metal pretreatment coating composition comprising: 50 to 300 ppm of dissolved Zr, 0 to 50 ppm of dissolved Cu, 0 to 100 ppm of Si0 2 , 150 to 2000 ppm of total Fluoride, 10 to 100 ppm of free Fluoride and a chelating agent.
• the zirconium-based pretreatment coating composition of the invention provides a pretreatment coating wherein the average total ratio of atomic % of Cu to atomic % of Zr in the pretreatment coating on the metal substrate is less than 1.1. In a further embodiment, this ratio ranges downward from, in order of increasing preference 1.10, 1.05, 1.0, 0.95, 0.90, 0.85, 0.80, 0.75, 0.70, 0.65, 0.60, 0.55, 0.50 and is not less than, in increasing order of preference 0.0001, 0.0005, 0.0010, 0.0050, 0.010, 0.050. In certain embodiments, for example where no added Cu is present in the coating composition, the ratio of Cu to Zr in the deposited coating may be zero.
• the invention is directed to a method for improving paint adhesion to a metal substrate comprising the steps of: providing a metal substrate;
• an aqueous, zirconium-based metal pretreatment coating composition comprising 50 to 300 ppm of dissolved Zr, 0 to 50 ppm of dissolved Cu, 0 to 100 ppm of Si0 2 , 150 to 2000 ppm of total Fluoride, 10 to 100 ppm of free Fluoride and a chelating agent thereby forming a pretreatment coating on the metal substrate wherein a chelating agent is present in an amount such that the average total ratio of atomic % of Cu to atomic % of Zr in the pretreatment coating on the metal substrate is equal to or less than 1.1 ; and applying a paint to the metal pretreatment coated metal substrate.
• the pretreatment coating can be used on a variety of metal substrates including cold rolled steel (CRS), hot-rolled steel, stainless steel, steel coated with zinc metal, zinc alloys such as electrogalvanized steel (EG), 55% Aluminum-Zinc alloy coated sheet steel, such as Galvalume®, galvanneal (steel sheet with a fully alloyed iron-zinc coating) (HI A), and hot-dipped galvanized steel (HDG), aluminum alloys such as AL61 1 1 and aluminum plated steel substrates.
• CRS cold rolled steel
• EG electrogalvanized steel
• HI A galvanneal (steel sheet with a fully alloyed iron-zinc coating)
• HDG hot-dipped galvanized steel
• AL61 1 1 aluminum plated steel substrates.
• the invention is directed to a coated substrate comprising a metal substrate having deposited on said metal a pretreatment coating comprising metal from the substrate, zirconium, oxygen, copper and optional elements fluorine and carbon; wherein average total ratio of atomic % of Cu to atomic % of Zr in the pretreatment coating on the metal substrate is equal to or less than 1.1.
• the coated substrate further comprises at least one paint applied to the pretreatment coating wherein the painted coated substrate achieves at least 95% paint remaining when tested according to ASTM 3330M (Revised Oct. 1, 2004).
• Figures 1A, IB, 1C, and ID are scanning electron microscope (SEM) images of pretreatment coatings on cold rolled steel;
• Figure 2 A is an SEM image of the sample shown in Figure 1A with several circled areas of interest
• Figure 2B is a graph of the chemical composition of the areas circled in Figure 2A;
• Figure 3 A is an SEM image of the sample shown in Figure IB with several circled areas of interest
• Figure 3B is a graph of the chemical composition of the areas circled in Figure 3 A;
• Figure 4 is a graph of an X-ray photoclcctron spectroscopy analysis of a pretreatment coating composition of Figure 1 A according to the invention.
• Figure 5 is a graph of an X-ray photoelectron spectroscopy analysis of the pretreatment coating composition of Figure IB.
• the present invention is directed to a metal pretreatment coating composition, and a method for applying the same, as well as to articles of manufacture comprising coatings according to the invention.
• the invention provides surprising improvements in performance in zirconium-based conversion coating pretreatments such as, by way of non-limiting example, zirconium-based conversion coatings deposited on a metal substrate by contact with a working bath containing dissolved zirconium in the coating compositions.
• zirconium-based conversion coatings such as, by way of non-limiting example, zirconium-based conversion coatings deposited on a metal substrate by contact with a working bath containing dissolved zirconium in the coating compositions.
• These conversion coating compositions are exemplified by aqueous coating baths comprising dissolved zirconium and free fluoride that form coatings comprising zirconium and oxygen.
• the baths are typically aqueous, neutral to acidic, and comprise dissolved zirconium, dissolved copper, either as an additive or as a trace element from water or metal substrates, and a source of fluoride.
• Optional components may be present including materials comprising one or more of silicon (e.g. silica, silicates, silanes), boron, yttrium, particular embodiments of which have no phosphates and no zinc, nickel, cobalt, manganese, and chromium.
• silicon e.g. silica, silicates, silanes
• boron boron
• yttrium particular embodiments of which have no phosphates and no zinc, nickel, cobalt, manganese, and chromium.
• Many zirconium-based coating baths contain copper, either as an additive or as a trace element from water or from metal workpieces being coated.
• the present inventors have discovered that copper from the zirconium-based coating bath that is deposited in the coating can negatively affect performance of the coated metal substrate, if present in amounts such that undesirable morphologies in the coating arise and/or in amounts above desirable levels.
• the coating baths typically are aqueous, neutral to acidic, and comprise dissolved zirconium, dissolved copper, a source of fluoride and counter ions for the dissolved metals, for example sulfates and/or nitrates.
• Optional components may be present including materials comprising one or more of silicon (e.g. silica, silicates, silanes), boron, yttrium.
• the zirconium-based pretreatment coating compositions may contain acid, generally a mineral acid, but optionally organic acids; and/or an alkaline source. The acid and/or alkali may be a source of other components in the composition, may be used to control pH or both.
• the zirconium-based pretreatment coating compositions according to the invention may likewise, consist essentially of or consist of the materials described herein.
• the coating composition according to the invention provides zirconium-based coatings having improved paint adhesion and maintained corrosion resistance. These and other benefits are achieved by adding to a zirconium-based coating composition, either a bath or the concentrate, a chelating agent, preferably a copper metal chelating agent, to control the amount of copper deposited onto the metal substrate by the zirconium-based pretreatment coating composition.
• a chelating agent preferably a copper metal chelating agent
• This chelating agent can be added to the zirconium-based pretreatment coating composition even where no copper is present in the unused zirconium-based pretreatment coating composition, as a protective agent to prevent later copper deposition as the bath ages and copper is incorporated into the bath as a trace element from water, such as from prior cleaning or rinse steps, and/or from metal workpieces being coated.
• the inclusion of the chelating agent also extends the pot life of the pretreatment coating bath because is allows for a wider range of immersion times without negative effects on paint adhesion or corrosion protection.
• a zirconium-based pretreatment coating composition comprising 50 to 300 ppm of dissolved Zr, 0 to 50 ppm of dissolved Cu, 0 to 100 ppm of Si0 2 , 150 to 2000 ppm of total Fluoride, 10 to 100 ppm of free Fluoride and a chelating agent.
• the composition may comprise amounts within the disclosed ranges, such as: 50, 60, 70, 80, 90, 100, 120, 130, 140 or 150 ppm to 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290 or 300 ppm of dissolved Zr; 0, 5, 10, 15, or 20 ppm to 25, 30, 35, 40, 45, or 50 ppm of dissolved Cu; 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 ppm to 60, 65, 70, 75, 80, 85, 90, 95 or 100 ppm of SiCb; 150, 170, 190, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, 500, 525, 550, 575, 600, 700, 800, 900, or 1000 ppm to 1 150, 1 170, 1 190, 1200, 1225, 1250, 1275, 1300, 1325, 13
• a zirconium-based pretreatment coating composition comprising 100 to 300 ppm of dissolved Zr, 0 to 50 ppm of dissolved Cu, 0, 25, 50, 75, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 or 2000 ppm to 2500, 3000, 4000, 4500 or 5000 ppm of S0 4 , 100 to 1600 ppm of total Fluoride, 10 to 200 ppm of free Fluoride and a chelating agent.
• the chelating agent may be any chelating agent capable of reducing the amount of copper deposited in the zirconium based coating.
• the chelating agent may be a copper metal chelator.
• a partial list of exemplary chelating agents, many of which are molecules having multiple carboxylic and/or phosphonic functional groups, that can be used in the present invention includes the following: adenine, adenosine, alanine, aminosalicylic acid, ascorbate/ascrobic acid, aspartate/aspartic acid, benzoic acid, citrate/citric acid, cyanuric acid, cysteine, cuprizone, diethanolamine, diethylenetriamine, diethylenetriamine- pentamethylene phosphonic acid, dihydroxybenzoic acid, dimethylenediamine,
• These chelating agents may be utilized according to the following methods: they may be incorporated into a pre-rinse applied prior to contacting the metal substrate with a zirconium-based pretreatment coating composition; the chelating agents may be
• the chelating agents may also be applied as a post-rinse applied after the metal substrate has been contacted with a zirconium-based pretreatment coating composition.
• the chelating agents are used a level sufficient to ensure that in the deposited pretreatment coating the average total ratio of the atomic % of Cu to the atomic % of Zr in the pretreatment coating on the metal substrate is equal to or less than 1.1, preferably from 0.9 to 0.02, and most preferably from 0.30 to 0.10.
• the amount of chelating agent in the coating composition may range from 1 Oppm to 2000ppm.
• the amount required is affected by, for example, the amount of copper present in the coating composition, the temperature of the coating bath, the substrate being coated, whether the composition is a concentrate or the working bath and the particular chelating agent being used.
• Chelating agents with multiple coordination sites may be used at lower levels.
• the chelating agent is present in an amount ranging from 25-100 ppm in the coating bath. More chelating agent may be added provided the concentration does not adversely affect bath performance.
• the amount of chelating agent in the pretreatment coating composition is an amount sufficient to achieve a desired Cu:Zr ratio in the deposited coating and preferably the chelating agent amount is at least, in increasing order of preference 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70 or 75 ppm and is at most, in increasing order of preference, 2000, 1500, 1000, 900, 800, 700, 600, 500, 400, 300, 200, 100 ppm.
• the average total ratio of atomic % of Cu to atomic % of Zr may range downward from, in order of increasing preference 1.10, 1.05, 1.0, 0.95, 0.90, 0.85, 0.80, 0.75, 0.70, 0.65, 0.60, 0.55, 0.50.
• copper is a desirable part of the composition and the coating.
• the ratio of copper to zirconium is desirably not less than, in increasing order of preference 0.0001, 0.0005, 0.0010, 0.0050, 0.010, 0.050.
• Zirconium-based pretreatment coatings of the invention may have a variety of components in the coating provided that the amount of copper in the coating is not such that undesirable coating morphology and performance failures result. Examples
• the immersion bath time for a pretreatment coating step is about 120 seconds, but during an assembly line stoppage this time can be 10 minutes or longer.
• an alternative protocol was developed by the present inventors. The process used in the experiments described in the present specification is as shown in TABLE 1 below.
• the standard pretreatment process for all of the data is as described below in TABLE 1.
• the Parco ® Cleaner 1533R is an alkaline cleaner available from Henkel Adhesive Technologies.
• the Ridosol 1270 is a basic nonionic surfactant and is available from Henkel Adhesive Technologies.
• the weight ratio of Parco to Ridosol used was 8.33 to 1.
• Aging of the cleaner was simulated by adding the oil Tirroil 906 available from Tirreno Industries, to age the cleaner at 4 grams/liter.
• the base pretreatment composition was a zirconium-based pretreatment.
• the electrodeposited paint coating used in all of the paint adhesion tests was BASF Cathoguard 31 OX available from BASF. This is a standard coating used in the automotive industry.
• the zirconium-based pretreatment bath used for Example 1 included 180 parts per million (ppm) of zirconium, 30 ppm of copper, 35 ppm of free and 400 ppm of total fluoride, 42 ppm of Si0 2 ; the zirconium-based pretreatment bath pH was set at 4.2 Two different batches of commercially available, cold rolled steel (CRS 1 and CRS 2), as is typically used in automobile manufacture, were processed according to Table 1. The zirconium coating weight in milligrams Zr per square meter was determined for each sample.
• X was determined using the following protocol. A sample area was cross hatched down to the level of the substrate with a razor using a line spacing of 1 millimeter and 6 lines for each direction. Then a 75 millimeter long strip of adhesive tape 20 millimeters wide was applied to the cross hatched area. The tape adhesively bonds to steel according to ASTM 3330M (Revised Oct. 1, 2004) with a 180 degree peel strength value of 430 N/m. After 5 to 10 seconds of adhesion, the tail end of the tape was grasped and pulled upward with a rapid jerking motion perpendicular to the paint. The percent paint remaining attached to the substrate (indicative of paint adhesion) was determined as a percentage of the area covered by the tape. The results of Example 1 are reported below in TABLE 2.
• Figures 1A and 1C are scanning electron microscope (SEM) photographs of
• Figures IB and ID are SEM photographs of CRS 2 coated with a pretreatment coating according to Example 1, using fresh 1533/1270, a Zr coating weight of 165 mg/m and a bake temperature of 375° F as described above (Sample 7).
• Sample 7 the CRS 2 sample exhibited poor paint adhesion.
• the photographs show that the deposited pretreatment coating of Sample 3 in Figures 1A and 1C was composed of much smaller substructures than that found in the pretreatment coating surface of Sample 7 in Figures IB and ID.
• the surface in Figures IB and ID had larger and more clumped looking substructures.
• Figures 2A and 2B are a further analysis of the Sample 3 surface shown in Figures 1 A and 1C.
• Figure 2A shows an SEM photograph of the pretreatment coating at a magnification of 15,000x and also shows three circles labeled 1, 2, and 3. Each of these areas was subjected to Auger Emission Spectroscopy (AES) to identify the elements and their levels found in each area of analysis. The results were evaluated by looking at the deviation from the baseline for each area, to make comparison possible the baselines were offset as can be seen.
• the units on the y-axis in Figure 2B are (counts/second) X 10 5 , that is, the y-axis amounts were increased by a factor of 100,000. The results show differences in the levels of copper between the three areas.
• the iron, zirconium and carbon levels were all very similar in the three areas.
• the largest substructure, area 1 had the highest level of copper.
• area 2 a very small substructure, had very little copper in it.
• area 3 which was taken between two larger substructures, showed a copper level that was between areas 1 and 2.
• the actual levels of copper were as follows: area 1 had a copper level of 27 atomic percent; area 2 had a copper level of 5 atomic percent; and area 3 had a copper level of 6 atomic percent. This represents a pretreatment coating (Sample 3) that led to good paint adhesion as shown in TABTE 2.
• Figures 3 A and 3B show a further analysis of the surface shown in Figures IB and ID (Sample 7).
• Figure 3 A shows an SEM photograph of the pretreatment coating at a magnification of 15,000x and also shows two circles labeled 4 and 5. Each of these areas was subjected to AES to identify the elements and their levels found in each spot of analysis. The results were evaluated by looking at the deviation from the baseline for each area, to make comparison possible the baselines were offset as can be seen.
• the units on the y-axis of Figure 3B are (counts/second) X 10 4 , that is, the y-axis amounts were increased by a factor of 10,000, therefore 1 unit in Figure 3B is equal to 10 units in Figure 2B.
• Area 4 is of a large substructure and the AES analysis showed that it had a very high level of copper, much higher than that found in the large substructure shown in Figures 2A and 2B, area 1.
• area 5 a small substructure showed lower levels of copper than area 4, but much higher than even area 1 of Figures 2A and 2B considering the differences in the units.
• the actual values for Sample 7, Figure 3B, were as follows: area 4 had a copper level of 31 atomic percent and area 5 had a copper level of 25 atomic percent, much higher on average than those of Sample 3, which had good paint adhesion.
• Figures 4 and 5 are graphical representations of the results from X-ray photoelectron spectroscopy (XPS) depth analysis of the two sample pretreatment coatings described in Figures 2 and 3, respectively.
• XPS X-ray photoelectron spectroscopy
• Figure 5 showing a graph of Sample 7, the sample exhibiting poor paint adhesion, showed that the copper levels in the deposited pretreatnient coating were much higher than in Sample 3, the pretreatnient coating exhibiting good paint adhesion, whose graph is shown in Figure 4. Both the atomic percentage and the area under the curve for the copper were much greater in Figure 5 (Sample 7) compared to Figure 4 (Sample 3).
• the peak atomic % Cu in Figure 4 was 33 atomic %.
• the peak atomic % Cu in Figure 5 at any depth was 42.73 atomic %.
• the pretreatment coating composition has sufficient chelating agent to ensure that the deposited pretreatment coating on the metal substrate has a average total ratio of the atomic % of copper to the atomic % of zirconium equal to or less than 1.1 , more preferably the ratio is from 0.9 to 0.02, and most preferably from 0.3 to 0.1. This ratio is determined from the average overall atomic percentages of the Zr and Cu in the coating not from the ratio at a single depth.
• Example 2 the control pretreatment coating composition was a zirconium- based coating bath, wherein the Zr level was 180 ppm , Cu was 30 ppm, total Fluoride was 400 ppm and free Fluoride was 35 ppm, the level of Si0 2 was 42 ppm.
• the test pretreatment coating composition was the same as the control and further comprising a chelating agent, tartrate introduced as tartaric acid at 50 ppm.
• compositions was adjusted to 4.0.
• the substrate was CRS that had been pre-cleaned with fresh Parco ® 1533 and rinsed as described in TABLE 1 above.
• the immersion time in the control and the test zirconium-based coating baths was either 4 minutes or 10 minutes, simulating a shorter and a longer line stoppage.
• a portion of each set of samples were then further coated with BASF Cathoguard 31 OX as described above and baked at 375° F. The baked samples were then tested for paint adhesion as described above.
• the coating weights of Zr in mg/m were determined for the samples.
• the average atomic percentage of Zr and Cu in the pretreatment coatings was determined for each sample. The results are present below in TABLE 3.
• Samples were then scribed to the CRS substrate and subjected to one of two corrosion performance tests.
• the first test was according to ASTM Bl 17 (Revised Dec. 15, 2007) for 500 hours.
• a second test a 31 cycle test, the sample panels were subjected to 31 cycles of a 24 hour testing protocol using a salt misting spray.
• the salt misting spray comprised 0.9% by weight sodium chloride, 0.1% by weight calcium chloride, and 0.075% by weight sodium bicarbonate at pH 6 to 9.
• the first 8 hours the panels were kept at 25° C and 45% Relative Humidity (RH) and misted 4 times during the 8 hours at time 0, 1.5 hours, 3 hours and 4.5 hours.
• RH Relative Humidity
• TEA triethanolamine
• the substrate was CRS and the pretreatment coating and BASF Cathoguard were applied as described below in TABLE 7.
• the zirconium-based coating bath included 180 ppm of Zr, 30 ppm of Cu, 35 ppm of free and 400 ppm total Fluoride and 42 ppm of Si0 2 .
• Samples were then tested for Zr coating weight in mg/m 2 , paint adhesion, and corrosion protection under ASTM Bl 17 for 500 hours.
• As a control samples were also prepared with a pretreatment coating of Bonderite ® 958 and Parcolene ® 91 as described in Example 3. The results are presented below in TABLE 8. Only a single concentration of TEA was tested, the same level as used for tartrate of 50 ppm.

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