MXPA99006739A - Aqueous phosphating composition and process for metal surfaces - Google Patents

Abstract

An aqueous zinc phosphate conversion coating that contains 5 to 50 g/L of phosphate ions, 0.2 to 10 g/L of zinc ions, and 0.5 to 4.0 g/L as hydroxylamine of a hydroxylamine source, and also:(1) contains 0.01 to 5.0 g/L polycarboxylic acid or salt thereof and/or starch phosphate;or (2) has a zinc ions/phosphate ions weight ratio below 0.27 and a zinc ions concentration of at least 2.0 g/L forms high quality zinc phosphating coatings on metal surfaces even if the surfaces have not been previously conditioned by contact with a dispersion of colloidal titanium.

Description

COMPOSITION OF AQUEOUS PHOSPHATATION AND PROCESS FOR. METALLIC SURFACES Field of the Invention The present invention relates to a treatment composition, more particularly to a liquid solution in water, which forms a zinc phosphate conversion coating on metal surfaces and the present invention also relates to a method for the treatment of metallic surfaces with said treatment composition. The invention is especially effective when applied to iron and steel, but can also be applied to various surfaces made of zinc or an alloy thereof and / or aluminum or an alloy thereof, such as, for example, alloys containing at least 55% atomic zinc or aluminum. Description of the Related Art Zinc phosphate treatments are carried out in order to provide corrosion resistance to metals such as iron and steel, as a lower coating for painting operations, and to provide lubrication in forging and drawing operations. This treatment is carried out by placing the workpiece in contact with the treatment composition, which is often referred to as "bathing" below, even when the contact is not necessarily carried out by immersion of the metal substrates. in the bathroom, for a sufficient time at an appropriate temperature. Spray and / or dip are typically used to achieve this contact. The overall process is usually carried out by the following steps. (1) Cleaning (2) Surface conditioning (3) Phosphate conversion treatment (4) Subsequent treatment A water rinse is typically used between each of these steps and the next of these steps, except between steps (2) and (3), in order to avoid the dragging of material from an upstream passage to a downstream passage. The cleaning step (1) is carried out in order to remove grease and other contaminants adhered on the work piece and to thereby provide a smooth execution of the downstream steps. An alkaline cleaner is typically used for this cleaning step. In the surface conditioning step (2), the workpiece typically comes into contact with a treatment bath containing colloidal titanium. This treatment results in a substantial acceleration of the film-forming reactions during the phosphate conversion treatment and thus enables the formation of a uniform, fine, dense conversion coating in a short period of time. The use of phosphate coatings as paint base coatings on automotive components requires high quality phosphate coatings that must exhibit good paint adhesion and corrosion resistance and the surface conditioning step has been considered essential for the production of coatings of this type. Step (3) of phosphate conversion treatment is carried out using various treatment bath compositions and treatment conditions whose particular selection depends on the specific objective. By way of example, in the case of paint base coating treatments for automotive components, the ingredients present in a zinc phosphate-type treatment bath will be phosphate ions, zinc ions, and other metal ions (e.g., nickel , manganese), and each of these components will offer specific properties to the final film. Other components typically present in baths of this type are nitrate, nitrite, chlorate, fluoroborate and fluorosilicate. A decrease in treatment temperature has been attempted in recent years and currently these treatments are carried out at temperatures of 40 ° C to 50 ° C during treatment times of approximately 1.5 to 3 minutes. The treatment is carried out frequently by immersion. The post-treatment step (4) is carried out, for example, in order to improve the corrosion resistance and adhesion of the paint. A treatment bath, which contains either exavalent chromium or free chromium, is used as the after-treatment agent. This step can be omitted according to the particular purpose of the application. High quality zinc phosphate conversion films used as base paint coatings on iron and steel can be evaluated by (1) the appearance of the conversion coating, (2) the weight of the coating, and (3) the P / (P + H) ratio in accordance with what is defined below. The following characteristics are essential, or if preferred, preferred, to qualify as "good" the appearance of a conversion coating: the conversion coating must be free of defects such as oxidation, blue color, and thin or incomplete coating. , and furthermore a columnar and / or nodular crystalline coating is preferred whose crystals are preferably microcrystalline, with sizes of approximately 1 to 5 micrometers (hereinafter known by the abbreviation "μm." The mass of the formed coating divided by the area of the surface that is being coated, a value also known as "coating weight" below, as a general rule, is preferred within a range of about 1 to 3 grams per square meter (hereinafter usually abbreviated "g / m2"). The relation P / (P + H) is calculated from the following equation: Ratio P / (P + H) = lp / (lp + lh) where Ih represents the inte X-ray diffraction nsity of the surface (020) of hope (zinc phosphate) and lp represents the intensity of X-ray diffraction from the surface (100) of phosphophyllite (zinc iron phosphate) or one of its analogues where manganese cations, nickel, cobalt, calcium, magnesium, copper and / or the like dissolved in the phosphating solution can replace some or all of the iron cations in the phosphophyllite itself. The P / (P + H) ratio is widely recognized as a characteristic value for zinc phosphate type films used as base coatings for iron and steel paint. P / (P + H) values of 0.8 to 1 are generally considered adequate to provide good conversion coatings for paint base coatings. A coating solution presented in Japanese Laid-open Patent Application (Kokai or not examined) No. Hei 1-123080 (123,080 / 1989) employing hydroxylamine sulfate (HAS) as an accelerator. The intention in this case is, by using this accelerator, to change the morphology of the film from platelet structures to columnar and / or nodular structures in a wide range of zinc concentrations. While Ni and Mn are mentioned as general complementary ions, neither the Detailed Description nor the Examples provide an explanation of how their addition amount should be determined. This reference also discloses a relatively large number of other patents wherein hydroxylamine sulfate is added to zinc phosphate solutions and further discloses patents in which an oxidizing agent is present, including U.S. Patent Nos. 2,743,204 and 2,298,280. Japanese Laid-open Patent Application No. Hei 1-123080 also teaches the treatment of the metal surface with a surface conditioner containing colloidal titanium before conversion treatment. It is noted that the source of hydroxylamine is added to the conversion bath presented in Japanese Patent Application No. Hei 1-123080 for the purpose of broadening the permissible range of zinc concentrations in the bath in which coatings can be obtained. desired conversion. In this reference, the concentration range of zinc is expressed by the ratio zinc ions / phosphate ions. The weight ratio zinc ions / phosphate ions is not greater than 0.27 while the concentration of zinc itself is 0.02% by weight to 0.2% by weight, which is equivalent to approximately 0.2 to 2 grams per liter of the total composition (usually abbreviated below as "g / L"). A phosphate conversion treatment bath presented in Japanese Laid-open Patent Application (Kokai or unexamined) No. Hei 5-195245 (195,245 / 1993) contains hydroxylamine (HAS), nickel ions, and manganese ions. The reference also teaches surface conditioning with a bath containing colloidal titanium before the conversion treatment. Japanese Patent Laid-Open No. Hei 5-195245 presents nickel ions and manganese ions as essential components in its treatment bath and also stipulates that the range between 1/25 and 1/10 is a preferred range for the weight ratio ions zinc / phosphate ions for the treatment bath of Japanese Patent Application Open (Kokai or unexamined) No. Hei 1-123080. The content of nickel ions in this case is specified from 0.02 to 0.15% by weight and the content of manganese ions is specified from 0.02 to 0.15% by weight. A weight ratio zinc ions / (manganese ions + nickel ions) of about 1/1 to 1.5 is specified.

The phosphate conversion treatment bath presented in Japanese Patent Application Open (Kokai or unexamined) No. Hei 5-195246 (195,246 / 1993) employs a combination of simple and complex fluoride, a chelating agent for iron, ions phosphate, a source of hydroxylamine and an oxidizing agent selected from water-soluble aromatic nitro organic compounds, salts of olibdic acid, and tungstic acid. This bath can efficiently form a highly corrosion-resistant phosphate conversion coating on various metal surfaces without requiring the use of the higher valence or divalent metal ions employed in the prior art. This treatment bath may also contain a colloidal titanium compound, in which case the conversion treatment and the surface conditioning can be carried out in a single step. The open patent applications mentioned above do not establish anything regarding the omission of the surface conditioning step, and in fact establish that the inclusion of a surface conditioning step is desirable. Furthermore, as a result of our investigations, we have found that the conversion treatment baths of Japanese Patent Application Open (Kokai or unexamined) No. Hei 1-123080 and No. Hei 5-195246, although they produce conversion coatings. even in the absence of a surface conditioning step, they are inadequate in the case where the object is the production of high quality conversion coatings applicable as paint base coatings. Problems that the invention must solve The present invention offers a treatment bath that can form a high quality phosphate coating on metal surfaces with or without the realization of a surface conditioning step. The present invention also offers a method for the treatment of metal surfaces. Surface conditioning with a treatment bath containing colloidal titanium has been essential to date, for example, in the case of phosphate treatments with the formation of high quality conversion coatings as typified by the paint base coatings for steel sheets for automotive use. The introduction of a conversion treatment bath that can form high quality conversion coatings even in the absence of a surface conditioning step will allow for conversion treatment installations that require less space and offer the advantage of making the amount of waste unnecessary. work related to the handling of the surface conditioning bath.

In addition, the present invention specifically provides a method that, even in the absence of a surface conditioning step, can form high quality zinc phosphate coatings, especially in articles that must have a corrosion resistance and for which of generating an adhesion between a film of paint, rubber, or plastic, and a surface of iron or steel. The zinc phosphate coating provided by the present invention can be used not only as a paint base coating but can also be used as an adhesion base coating, for example, in the case of the adhesion of resin or rubber films on a surface of iron or steel. SUMMARY OF THE INVENTION It has been considered that high quality zinc phosphate conversion coatings can be produced on a stable basis, without resorting to the use of a surface conditioning step by the use of hydroxylamine in combination with acid (s). ) polycarboxylic acid (s) or salt (s) thereof and / or starch phosphate either maintaining a suitable concentration for zinc ions or an upper limit on the ratio zinc ions / phosphate ions present in the conversion treatment bath . DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS A preferable composition according to a first embodiment of the present invention is an aqueous zinc phosphate solution containing phosphate ions of 5 to 50 g / L, zinc ions of 0.2 to 10, or preferably 2.0 to 10 g / L, a source of hydroxylamine in an amount that provides 0.5 to 4.0 g / L of hydroxylamine, and 0.01 to 5.0 g / L of at least one selection within the group consisting of polycarboxylic acids, salts thereof, and starch phosphate. It is believed that the hydroxylamine source increases the reactivity of the conversion of the phosphate treatment solution. Thus, the source of hydroxylamine is a component that makes it possible to omit the step of surface conditioning. The chemical nature of the hydroxylamine source added to the coating treatment solution according to the present invention is not critical and may, for example, be a complex hydroxylamine salt or salt. Specific preferred examples are the salts of phosphate, nitrate, and hydroxylamine sulfate and mixtures thereof. In the present invention the amounts of hydroxylamine are reported in terms of the stoichiometric equivalent of hydroxylamine as calculated from the addition of the hydroxylamine source. For the example of hydroxylamine sulfate as a source of hydroxylamine, the addition of 10 g / L of hydroxylamine sulfate provides 4.0 g / L of hydroxylamine. The source of hydroxylamine is preferably added to provide 0.5 to 4.0 grams of hydroxylamine per liter. Concentrations below this range are without adequate effect and therefore result in a poor coating in the absence of a surface conditioning treatment. Values above 4.0 g / L have a remarkable tendency to produce defects such as blue color. The addition of polycarboxylic acid and / or salt thereof or starch phosphate to the zinc phosphate treatment solution supports and facilitates the production of high quality zinc phosphate conversion coatings by controlling the weight of the conversion coating. and inhibits the thickening of the crystals in the conversion coating. However, an addition greater than 5 g / L has the opposite effect of inhibiting the conversion reactivity. A carboxylic acid is a compound containing at least two carboxyl portions in each molecule and in the context of the present invention also encompasses hydroxycarboxylic acids containing one or more hydroxyl portions in addition to at least two carboxyl portions. Typical examples of the polycarboxylic acids of the present invention are citric acid, tartaric acid, succinic acid, ethylenediaminetetraacetic acid, and nitrilotriacetic acid, with the first three of these forming a preferred group and citric acid being especially preferred. Their salts are exemplified by the sodium, potassium, ammonium and iron ammonium salts. A composition according to a second preferred embodiment of the present invention is an aqueous zinc phosphate solution containing phosphate ions in a concentration of 7.5 to 50 g / L, zinc ions in a concentration of 2 to 10 g / L, and a source of hydroxylamine in an amount that provides hydroxylamine at a concentration of 0.5 to 4.0 g / L and wherein the weight ratio zinc ions / phosphate ions is not greater than 0.27. The use of this treatment solution at temperatures of 40 ° C to 50 ° C for treatment times of at least 1 minute produces high quality zinc phosphate coatings consisting mainly of nodular and / or columnar iron zinc phosphate crystals. . You can use either the dip or spray as a method of treatment. At least 7.5 g / L of phosphate ions are required to avoid a ratio of zinc ions / phosphate ions that is too high even with the minimum concentration of zinc suitable for this modality. While a conversion coating is produced at phosphate ion values in excess of 50 g / L, such levels are not economical due to the increased consumption of reagent, for example, by entrainment. Suitable concentrations of zinc ions for this second preferred embodiment are between 2 and 10 g / L. While a conversion coating can be obtained in zinc ion concentrations below 2 g / L even in the absence of a surface conditioning step, the coating by such coatings has a remarkable tendency to be thin or incomplete. Concentrations of zinc ions above 10 g / L make the weight of the resulting conversion film too large, making it unsatisfactory as a high quality paint base coating. The type of hydroxylamine source and its content range are the same as in the first preferred specific modality. The weight ratio zinc ions / phosphate ions should be at 0.27 or below. Precipitation in the conversion treatment bath is observed in values higher than 0.27; this not only affects the stability of the treatment bath but also prevents the production of normal conversion coatings. The aqueous zinc phosphate solutions of the first preferred embodiment and the second preferred embodiment may also contain ferrous ions. However, since ferrous ions are supplied by etching an iron or steel workpiece by the conversion treatment solution itself, ferrous ions are typically present to some degree even in the absence of the deliberate addition of said ions. ions to the treatment bath. At least a selection of the following may be added in order to obtain additional improvements in the conversion treatment activity and / or additional improvements in relation to the quality of the conversion coating: nickel ions, manganese ions, nitrate ions, fluorine (as a fluorine chemical compound), and complex fluoride ions. The concentrations of the ferrous ions, nickel ions, manganese ions, nitrate ions, fluorine and complex fluoride ions are preferably within the range of 0.01 to 5 g / L. In a preferred method for supplying the reagents, the treatment bath receives a supply composition comprising an aqueous solution containing zinc ions, phosphate ions, and a hydroxylamine source wherein the total concentration of these species is at least 15% in weigh. The invention can be further observed by taking into account the non-limiting working examples and comparison examples presented below. The following tests were performed in order to demonstrate the beneficial effects of the present invention in its first preferred embodiment in accordance with that described above. The test substrates were laminated steel panels with a thickness of 0.8 millimeters, a unit usually abbreviated below either singular or plural as "mm", and dimensions greater than 70 mm x 150 mm. The conversion treatment was carried out using the conversion treatment solutions reported in the Table 1 and the properties of the resulting coatings were tested. Test panels treated by conversion were also painted in accordance with what was described below in order to test the performance of the paint application.

Process steps (1) Fat removal. The removal of grease is carried out using an alkaline grease remover FINECLEANER® L4460 from Nihon Parkerizing Co., Ltd. The conditions were as follows: 43 ° C, 120 seconds, sprayed. Table 1 Composition Concentration in g / L in the composition of: for ions hydroxyl ions ions ions ions fluorine P04"3 amine Zn ++ Ni ++ Mn ++ Fe ++ Example 1 15 2 2 0 0 0 0 Example 2 15 2 2 1 0 0.01 0.2 Example 3 20 4 5 1 0. 5 0.01 0.2 Example 4 15 2 2 1 0 0.01 0.2 Example 5 15 2 2 1 0 0.01 0.2 Example 6 15 2 2 1 0 0.01 0.2 Example 7 15 2 2 1 0.5 0.01 0.2 Ex. Comp.l 16 0 2 1 0 0.01 0.2 Ex. Comp.2 15 0.4 2 1 0 0.01 0.2 Ex. Comp.3 15 5 2 1 0 0.01 0.2 Ex. Comp.4 15 2 2 0 0 0.01 0.2 Ex. Comp.5 15 2 2 1 0 0.01 0.2 Composition Another additional solute, optionally for example 1 Ferric ammonium citrate 2.0 Example 2 Ferric ammonium citrate 2.0 Example 3 Ferric ammonium citrate 2.0 Example 4 Sodium tartrate 2.0 Example 5 Sodium succinate 2.0 Example 6 starch phosphate 1.0 Example 7 citric acid 2.0 Ex. Comp. 1 Ex. Comp. 2 starch phosphate 1.0 Ex. Comp. 3 starch phosphate 1.0 Ex. Comp. 4 Ex. Comp. 5 Abbreviations and other notes on Table 1 and following «Ex. Comp. »Refers to« Comparison example ». The hydroxylamine was supplied to the bath by the addition of hydroxylamine sulfate, ie, (NH2OH) 2? 2 SO4. The fluorine was supplied to the bath by the addition of hydrofluoric acid, that is, HF. (2) Rinse with water (tap water). The conditions were as follows: room temperature (i.e., 18 to 25 ° C, 30 seconds, sprayed.) (3) Zinc phosphate conversion treatment The treatment compositions were as reported in Table 1. The conditions of The process was as follows: 43 ° C, 120 seconds, immersion. (4) Water rinse (tap water) The process conditions were as follows: room temperature, 30 seconds, spray. (5) Rinse with deionized water, with a specific electrical conductivity no greater than 0.2 microSiemens per centimeter The process conditions were as follows: room temperature, 20 seconds, spray. (6) Drainage and drying. The conditions of the process were the following: 110 ° C, air, 180 seconds. Painting (1) Electro-paint by the use of cationic electro-paint GT-10B® by Kansai Paint Kabushiki Kaisha. The conditions were the following: bath temperature: 28 ° C voltage: 200 volts current application time: 180 seconds coating thickness: 20 μm baking: 170 ° C, residence time 20 minutes (2) An intermediate coating was applied using a melamine-alkylated TP-65 8160® paint from Kansai Paint Kabushiki Kaisha. The conditions were the following: coating thickness: 40 μm baking: 140 ° C, residence time 20 minutes (3) A top coat was applied using a melamine-alkyd paint NEO6000 D40® from Kansai Paint Kabushiki Kaisha. The conditions were the following: coating thickness: 40 μm baking: 140 ° C, residence time 20 minutes Methods for evaluating conversion coatings (1) Appearance of the coating. The appearance was evaluated visually. (2) Coating weight. This was calculated from the weight difference before and after washing with an aqueous solution containing 50 g / L of Cr03. (3) Size of the coating crystals and coating morphology. The coating morphology was revised and the crystal size was measured (unit: μm) using a scanning electron microscope from Nippon Denshi Kabushiki Kaisha. (4) The ratio P / (P + H) The diffraction intensities of the surface (100) of phosphophyllite and the surface (020) of hopeite were measured using a X-ray diffraction instrument Geiger Flex 2028 from Rigaku Denki Kabushiki Kaisha . Evaluation methods of painted panels (1) Paint adhesion test (adhesion test, water resistance, secondary) The test panel after processing until electro painting including it was immersed in deionized water at a temperature of 40 ° C for 240 hours. The test panel was then removed from the water and a cross-linked pattern of 100 units was marked on the panel with a sharp marker to the steel-based metal: 11 parallel lines were first marked at 1 mm interval and another 11 parallel lines were also marked. at 1 mm intervals they were marked perpendicular to the first set of lines. The pattern was peeled with a cellophane tape and the number of pictures peeled at least 50% was counted. (2) Salt Water Spray Test Using a sharp cutter, a cross was marked to the steel base metal on the test panel after processing until the application of electro paint, including such application. The test panel was then subjected to a spray test with 5% salt water (according to Japanese industrial standard Z-2371) for 1,000 hours. The value reported is the width in pi of the ampoule in the paint film produced along the scratch, taking into account both sides. (3) Exposure to the outside with salt water addition Using a sharp cutter, a cross was marked to the steel base metal in the test panel after processing until the application of the top coat, including said application. The panel was then exposed abroad for 3 months in Hiratsuka, Kanagawa Prefecture, Japan. The panel was splashed with 5% salty water once a week during the exposure period. The reported value is the width in mm of the blister in the paint film produced along the scratch taking both sides into account. Results of the evaluations of the panels treated by conversion Table 2 indicates the results of the evaluations of the panels treated by conversion and of the painted panels. Table 2 Appearance Result of Reverse-Test Weight Morphology for: g / m2 coating conversion Example 1 Nodular excellent example 2.6 Example 2 Nodular excellent 2.4 Example 3 Nodular excellent 2.4 Example 4 Nodular excellent 2.5 Example 5 Nodular excellent 2.5 Example 6 Excellent nodular 2.5 Example 7 excellent nodular 2.5 Ex. Comp.l without coating without crystals Ex. Comp.2 without coating without crystals Ex. Comp.3 blue color without crystals Ex. Comp.4 excellent nodular 2.9 Ex. Comp.5 excellent nodular 2.9 Result of Reason Size Loss of Spray test for: crystals, P / (P + H) paint,% salt water, μm of squares mm Example 1 2-3 0.95 0 1.5 Example 2 2-3 0.94 0 1.4 Example 3 2-3 0.95 0 1.3 Example 4 2-3 0.95 0 1.3 Example 5 2-3 0.94 0 1.3 Example 6 2-3 0.96 0 1.4 Example 7 2-3 0.94 0 1.3 Ex. Comp .1 - - 75 2.9 Ex. Comp.2 - - 70 3.6 Ex. Comp .3 - - 30 3 Ex. Comp .4 3-4 0.95 0 2 Ex. Comp.5 3-4 0.95 0 1.8 Outdoor Exposure Test test for: with salt water, mm Example 1 0.4 Example 2 0.3 Example 3 0.3 Example 4 0.3 Example 5 0.4 Example 6 0.3 Example 7 0.3 Ex. Comp .1 2.5 Ex. Comp.2 2.3 Ex. Comp.3 2.4 Ex. Comp.4 0.6 Ex. Comp .5 0.5 The results in Table 2 show that the present invention offers good results for the conversion coating for all criteria: appearance of conversion, coating weight, size of coating crystals, morphology of the coating crystals , and ratio P / (P + H). The results in Table 2 also confirm that the present invention offers an excellent paint application capacity even in the absence of a surface conditioning step. The following remaining tests were performed in order to demonstrate the beneficial effects of the present invention in its second preferred embodiment in accordance with what is described above. Except in the case of the phosphate conversion coating compositions used, these tests were carried out in the same manner as described above and in the same type of substrates. The conversion coating treatment solutions are described in Table 3 and the results of the tests are described in Table 4. Table 3 Composition Concentration in g / L in the composition of: for ions hydroxyl ions ion ions fluorine ions P04 -3 amine Zn ++ Ni ++ Mn ++ Fe ++ Example 8 17 1.2 4 0 0 0 0 Example 9 17 1.2 4 0 0 0.01 0.2 Example 10 20 1.2 5 1 0 0.01 0.2 Example 11 25 2.8 5 1 0 0.01 0.2 Example 12 15 1.2 2 1 0 0.01 0.2 Example 13 30 1.2 7 1 0 0.01 0.2 Example 14 20 1.2 5 1 0.5 0.01 0.2 Ex. Comp .6 17 0.4 4 0 0 0.01 0.2 Ex. Comp .7 35 4.8 8 1 0 0.01 0.2 Ex. Comp .8 15 1.2 1 1 0 0.01 0.2 Ex. Comp .9 40 1.2 11 1 0 0.01 0.2 Ex. Comp .10 15 4.8 3 1 0 0.01 0.2 Composition for Reason (zinc ions): (phosphate ions) by weight Example 8 0.24 Example 9 0.24 Example 10 0.25 Example 11 0.2 Example 12 0.13 Example 13 0.23 Example 14 0.25 Ex. Comp.6 0.24 Ex. Comp .7 0.23 Ex. Comp.8 0.07 Ex. Comp.9 0.28 Ex. Comp.10 0.2 Table 4 Appearance Result of Reverse-test Weight Morphology for: Conversion coating, g / m2 / Example 8 nodular excellent 3 Example 9 excellent nodular 2.9 Example 10 excellent nodular 2.9 Example 11 excellent nodular 3 Example 12 excellent nodular 3 Example 13 excellent nodular 3 Example 14 excellent nodular 2.8 Ex. Comp.6 without coating without crystals Ex. Comp .7 excellent nodular up to 12 sheets Ex. Comp.8 Nodular coating 1.4 incomplete Ex. Comp .9 excellent nodular up to 10.7 leaves Ex. Comp.10 blue color without crystals Result of Reason Size Loss of Spray test for: crystals. P / (P + H) paint,% salt water, μm of frames mm Example 8 4-5 0.95 0 2 Example 9 3-4 0.94 0 1.8 Example 10 3-4 0.96 0 1.5 Example 11 4-5 0.94 0 2.1 Example 12 3-4 0.97 0 1.8 Example 13 3-4 0.94 0 1.9 Example 14 3-4 0.95 0 1.8 Ex. Comp .6 - - 70 4.5 Ex. Comp .7 10-11 0.94 10 2.5 Ex. Comp .8 5-6 0.95 5 3 Ex. Comp .9 9-10 0.93 40 3.8 Ex. Comp.10 - - 36 4.3 Exposition result to the extended test for: with salt water,] [tim Example 8 0. 5 Example 9 0.4 Example 10 0.4 Example 11 0.4 Example 12 0.5 Example 13 0.4 Example 14 0.3 Ex. Comp .6 2.5 Ex. Comp .7 0.7 Ex. Comp .8 0.6 Ex. Comp .9 0.8 Ex. Comp.10 2.2 Benefits of the invention The results reported in Tables 1 to 4 confirm that the present invention offers high quality conversion coatings even in the absence of a surface conditioning treatment.

Claims (1)

CLAIMS 1. A liquid composition suitable for forming a zinc phosphate conversion coating on a metal surface by contact and reaction between them, said liquid composition comprising water and the following dissolved components: (A) a concentration of 5 to 50 g / L of phosphate ions; (B) a concentration of 0.2 to 10 g / L of zinc ions; (C) the source of hydroxylamine in an amount that offers a concentration of 0.5 to 4.0 g / L of stoichiometric equivalent of hydroxylamine; and (D) at least one of the components (D1) and (D2) in accordance with the following: (D1) a concentration of 0.01 to 5.0 g / L in total of at least one substance selected from the group consisting of of polycarboxylic acids, salts thereof, and starch phosphate; (D.2) a concentration of zinc ions that is at least 2.0 g / L and has a relationship with the concentration of phosphate ions in the same liquid composition that is not greater than 0.27: 1.0. . A liquid composition according to claim 1, wherein the component (D1) is present and includes at least one substance selected from the group consisting of citric acid, succinic acid, tartaric acid, and salts of citric, succinic and tartaric acids . A liquid composition according to claim 1, wherein the component (D.2) is present. A liquid composition according to claim 3, further comprising at least one substance selected from the group consisting of ferrous ions, nickel ions, manganese ions, nitrate ions, fluorine in the form of a soluble fluorine compound, and fluoride ions complex. A liquid composition according to claim 2, further comprising at least one substance selected from the group consisting of ferrous ions, nickel ions, manganese ions, nitrate ions, fluorine in the form of a soluble compound of fluorine, and complex fluoride ions . A liquid composition according to claim 1, further comprising at least one substance selected from the group consisting of ferrous ions, nickel ions, manganese ions, nitrate ions, fluorine in the form of a soluble fluorine compound, and complex fluoride ions . A process for the formation of a zinc phosphate conversion coating layer on a surface of a metal substrate that has not undergone surface conditioning with a treatment bath containing colloidal titanium by contacting the surface of the substrate metal with an aqueous phosphating solution according to any one of claims 1 to 6. A process according to claim 7, wherein the aqueous phosphating solution is maintained at a temperature comprised within a range of 40 to 50 ° C for a time. of contact of at least

1.0 minute. A process according to claim 8, wherein the aqueous phosphating solution is recharged during use by the addition of a volume of supply composition which is an aqueous composition containing zinc ions, phosphate ions, and a source of hydroxylamine in a total concentration of these species which is at least 15% by weight. A process according to claim 7, wherein the aqueous phosphating solution is recharged during use by the addition of a volume of supply composition which is an aqueous composition containing zinc ions, phosphate ions, and a source of hydroxylamine in a total concentration of these species which is at least 15% by weight.