JP4276689B2 - Cationic electrodeposition coating method and metal substrate coated with cationic electrodeposition - Google Patents

Description

  The present invention relates to a metal surface treatment liquid, particularly a metal surface treatment liquid suitable for cationic electrodeposition coating, and a metal surface treatment method.

  Conventionally, surface treatment has been performed to impart corrosion resistance to various metal substrates. In particular, zinc phosphate treatment has been generally used for metal substrates constituting automobiles. However, this zinc phosphate treatment has a problem that sludge is generated as a by-product. For this reason, the next generation surface treatment which does not use zinc phosphate is calculated | required, and the surface treatment by a zirconium ion is one of them (for example, refer patent document 1).

  On the other hand, a cationic base electrodeposition coating is applied after the surface treatment to a metal base material constituting an automobile, which requires high anticorrosion properties. The reason why the cationic electrodeposition coating is applied is that the coating film obtained by the cationic electrodeposition coating is excellent in anticorrosion, and can be applied to every corner of an automobile body having a complicated shape. That is, it has a so-called “throwing power”.

However, recently, when cationic electrodeposition coating is performed on a metal base material that has been surface-treated with zirconium ions, it may be difficult to obtain a sufficient effect on the throwing power. It has been found that the throwing power may not be sufficient. Thus, when cationic electrodeposition coating is performed, sufficient corrosion resistance cannot be obtained unless the throwing power is sufficient.
Japanese Patent Application Laid-Open No. 2004-218070

  The present invention provides a surface treatment with zirconium ions that can exhibit sufficient throwing power and is excellent in anticorrosion properties when cationic electrodeposition is applied to a surface-treated metal substrate. With the goal.

The present invention is as follows.
(1) A metal surface treatment liquid for cationic electrodeposition coating containing zirconium ions and tin ions and having a pH of 1.5 to 6.5, wherein the concentration of the zirconium ions is 10 to 10,000 ppm, and the zirconium A metal surface treatment solution for cationic electrodeposition coating, wherein the concentration ratio of tin ions to ions is 0.005 to 1 in terms of mass.

  (2) A metal surface treatment liquid for cationic electrodeposition coating further comprising a polyamine compound as the metal surface treatment liquid for cationic electrodeposition coating (1).

  (3) A metal surface treatment liquid for cationic electrodeposition coating further containing copper ions as the metal surface treatment liquid for cationic electrodeposition coating of (1) to (2) above.

  (4) The metal surface treatment liquid for cationic electrodeposition coating of (1) to (3) above further contains fluorine ions, and the free fluorine ion amount is 0.1 to 50 ppm when the pH is 3.0. A metal surface treatment solution for cationic electrodeposition coating.

  (5) A metal surface treatment solution for cationic electrodeposition coating further containing a chelate compound as the metal surface treatment solution for cationic electrodeposition coating of (1) to (4) above.

  (6) The metal surface treatment liquid for cationic electrodeposition coating in which the chelate compound is sulfonic acid as the metal surface treatment liquid for cationic electrodeposition coating of (5) above.

  (7) A metal surface treatment solution for cationic electrodeposition coating further comprising an oxidizing agent as the metal surface treatment solution for cationic electrodeposition coating of (1) to (6) above.

  (8) The metal surface treatment solution for cationic electrodeposition coating according to any one of (1) to (7), further comprising aluminum ions and / or indium ions.

  (9) A metal surface treatment method including a step of performing a surface treatment on a metal substrate using the metal surface treatment liquid for cationic electrodeposition coating according to (1) to (8) above.

  (10) A metal substrate on which a film is formed by surface treatment, obtained by the metal surface treatment method of (9) above.

  (11) A metal substrate in which the element ratio of zirconium / tin in the film formed on the metal substrate of (10) is 1/10 to 10/1 in terms of mass.

  (12) Using the metal surface treatment liquid for cationic electrodeposition coating described in (1) to (8) above, a step of performing a surface treatment on a metal substrate, and a step of performing the surface treatment on the metal substrate A method of cationic electrodeposition coating, comprising a step of performing cationic electrodeposition coating.

  (13) A cationic electrodeposition-coated metal substrate obtained by the cationic electrodeposition coating method of (12) above.

  That is, the metal surface treatment solution for cationic electrodeposition coating of the present invention is a chemical conversion treatment solution containing zirconium ions and tin ions and having a pH of 1.5 to 6.5, and the concentration of the zirconium ions is 10 to 10,000 ppm. And content of the tin ion with respect to the said zirconium ion is 0.005-1 in mass conversion. Furthermore, a polyamine compound, copper ions, fluorine ions, chelate compounds, oxidizing agents, and rust inhibitors may be included. When fluorine ions are included, the amount of free fluorine ions when the pH is 3.0 may be 0.1 to 50 ppm.

  The metal surface treatment method of the present invention includes a step of performing a surface treatment on a metal substrate using the previous metal surface treatment liquid.

  A film obtained by the previous surface treatment is formed on the surface-treated metal substrate of the present invention. The element ratio of zirconium / tin in the film may be 1/10 to 10/1 in terms of mass.

  The cationic electrodeposition coating method of the present invention includes a step of performing a surface treatment on a metal substrate using the previous metal surface treatment solution, and a cationic electrodeposition coating on the metal substrate subjected to the surface treatment. The process of performing.

  The metal substrate coated with cationic electrodeposition according to the present invention is obtained by the previous coating method.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention contains tin ions in addition to zirconium ions, so that the throwing power is improved when cationic electrodeposition coating is performed after forming a chemical conversion film with this treatment liquid. It is thought to do. Although the reason is not clear, it can be considered as follows.

  That is, when zirconium ions are used alone, the formation of the oxide film is considered to be performed simultaneously with the etching of the metal substrate in an acidic atmosphere. However, on the cold-rolled steel sheet, there are segregated materials of compounds containing silicon and carbon in addition to silica, and such portions are difficult to be etched. For this reason, the film formation by a zirconium oxide is not performed uniformly, but the part in which the film was not formed exists. Since the current flow is different between the portion where the film is formed and the portion where the film is not formed, electrodeposition is not performed uniformly, and as a result, it is considered that sufficient throwing power cannot be obtained.

  Here, when tin ions are present, it is considered as follows. Since tin ions are less susceptible to influence on the steel plate than zirconium ions, it is easy to form an oxide film on the substrate. Although tin ions do not specifically form a film on the portion where zirconium ions are difficult to precipitate, tin ions do not form or do not form an oxide film on a specific portion. As a result, the tin ions compensate for the portion where the zirconium ions could not form a film, thereby forming the film.

  By including a polyamine compound, the metal surface treatment liquid for cationic electrodeposition coating of the present invention can improve adhesion to the cationic electrodeposition coating film, and as a result, clears the SDT test which is a more severe condition. It becomes possible. Moreover, the metal surface treatment liquid for cationic electrodeposition coating of the present invention can improve corrosion resistance by containing copper ions. The reason is not clear, but it is thought that some interaction is acting between copper and zirconium during film formation. Furthermore, when the metal surface treatment liquid for cationic electrodeposition coating of the present invention contains a large amount of metal other than zirconium, it can stably form a zirconium oxide film by containing a chelate compound. This is presumably because the chelate compound captures metal ions that precipitate more easily than zirconium.

  The metal surface treatment solution for cationic electrodeposition coating of the present invention is a chemical conversion treatment solution containing zirconium ions and tin ions and having a pH of 1.5 to 6.5.

  The concentration of the zirconium ions is 10 to 10000 ppm. If it is less than 10 ppm, sufficient corrosion resistance cannot be obtained because the deposition of the zirconium film is not sufficient, and even if it exceeds 10000 ppm, the deposited amount of the zirconium film does not increase, and the adhesion of the coating film decreases to prevent corrosion performance such as SDT. May be inferior, and the effect corresponding to it may not be obtained. The preferable lower limit value and upper limit value are 100 ppm and 500 ppm, respectively.

In addition, the description about the density | concentration of the metal ion in this specification shall represent with the metal element conversion density | concentration which paid its attention only to the metal atom in the complex or oxide, when the complex or oxide is formed. . For example, the metal element equivalent concentration of zirconium of complex ion ZrF ₆ ²⁻ (molecular weight 205) 100 ppm is calculated to be 44 ppm by calculation of 100 × (91/205). In the metal surface treatment solution for cationic electrodeposition coating of the present invention, even if a part of the metal compound (zirconium compound, tin compound, copper compound or other metal compound) exists in a nonionic state such as an oxide. The ratio is negligible and is considered to exist almost as a metal ion. Therefore, the metal ion concentration in the present specification refers to the metal ion concentration when 100% dissociates and exists as a metal ion regardless of whether or not a part of the metal ion exists as a non-ion.

  The tin ions contained in the metal surface treatment solution for cationic electrodeposition coating of the present invention are preferably divalent cations. At other valences, the intended effect may not be obtained. However, the tin ion is not limited to a divalent cation, and any tin ion that can be deposited on a metal substrate can be used in the present invention. For example, when a tin ion forms a complex, it may be a tetravalent cation, which can also be used in the present invention. The density | concentration of the said tin ion is 0.005-1 in mass conversion with respect to the density | concentration of the said zirconium ion. If it is less than 0.005, the effect of addition cannot be obtained, and if it exceeds 1, zirconium may be difficult to precipitate. Preferred lower and upper limits are 0.02 and 0.2, respectively. However, since the effect of the present invention may not be obtained if the total amount of zirconium ions and tin ions is too small, the total of the concentration of zirconium ions and the concentration of tin ions in the metal surface treatment liquid of the present invention. However, it is preferable that it is 15 ppm or more.

  As content of the tin ion in the metal surface treatment liquid of this invention, it is preferable that it is 1-100 ppm. When it is less than 1 ppm, the precipitation of tin on the portion where zirconium cannot form a film becomes insufficient, and the anticorrosion properties such as SDT tend to be poor. When it exceeds 100 ppm, the zirconium film is difficult to deposit, and the corrosion resistance and the coating appearance are likely to be inferior. The content is more preferably 5 to 100 ppm, and further preferably 5 to 50 ppm.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention has a pH of 1.5 to 6.5. If it is less than 1.5, the metal substrate is not sufficiently etched, so that the amount of the film is reduced and sufficient anticorrosion properties cannot be obtained. In addition, the stability of the treatment liquid may not be sufficient. On the other hand, if it exceeds 6.5, etching may be excessive and sufficient film formation may not be possible, or the amount and thickness of the film may be uneven, which may adversely affect the appearance of the coating. The lower limit value and the upper limit value are preferably 2.0 and 5.5, respectively, and more preferably 2.5 and 5.0.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention may further contain a polyamine compound in order to enhance the adhesion with the cationic electrodeposition coating film formed after the surface treatment. The polyamine compound used in the present invention is considered to have an essential meaning in that it is an organic molecule having an amino group. That is, although the following is speculated, it is considered that the amino group is incorporated into the film by a chemical action with zirconium oxide deposited as a film on the metal substrate or the metal substrate. Moreover, it is thought that the polyamine compound which is an organic molecule contributes to adhesiveness with the coating film provided on the metal substrate in which the said film | membrane was formed. Therefore, when a polyamine compound which is an organic molecule having an amino group is used, the adhesion between the metal substrate and the coating film is remarkably improved, and excellent corrosion resistance can be obtained. Examples of the polyamine compound include aminosilane hydrolyzed condensates, polyvinylamine, polyallylamine, and water-soluble phenol resins having an amino group. An aminosilane hydrolyzed condensate is preferred because the amount of amine can be adjusted freely. Accordingly, the metal surface treatment liquid for cationic electrodeposition coating of the present invention includes, for example, a metal surface treatment liquid for cationic electrodeposition coating containing a hydrolysis condensate of zirconium ion, tin ion, and aminosilane, zirconium ion, tin ion, And a metal surface treatment solution for cationic electrodeposition coating containing polyallylamine and a metal surface treatment solution for cationic electrodeposition coating containing a water-soluble phenol resin having zirconium ions, tin ions and amino groups. Moreover, you may contain the fluorine mentioned later in these metal surface treatment liquids for cationic electrodeposition coating.

  The aminosilane hydrolyzed condensate is obtained by hydrolytic condensation of an aminosilane compound. Examples of the aminosilane compound include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycol. Sidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldi Ethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (amino Ethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl- N- (1,3-dimethyl-butylidene) -propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyltriethoxysilane It can be mentioned silane coupling agent having an amino group of emissions, and the like. Moreover, as what is marketed, "KBM-403", "KBM-602", "KBM-603", "KBE-603", "KBM-903", "KBE-903", "KBE-9103" , “KBM-573”, “KBP-90” (both trade names, manufactured by Shin-Etsu Chemical Co., Ltd.), “XS1003” (trade names, manufactured by Chisso Corporation), and the like can be used.

  Hydrolysis condensation of the aminosilane can be performed by methods well known to those skilled in the art. Specifically, it can be carried out by adding water necessary for hydrolyzing an alkoxysilyl group to at least one aminosilane compound, and heating and stirring as necessary. The degree of condensation can be controlled by the amount of water used.

The higher the degree of condensation of the aminosilane hydrolyzed condensate, the more preferable it is because zirconium tends to be taken into it when it precipitates as an oxide. For example, in the total amount of aminosilane, the proportion of aminosilane of dimer or higher is preferably 40% or more in terms of mass, more preferably 50% or more, further preferably 70% or more, 80% More preferably, it is more than the above. For this reason, when aminosilane is reacted in a hydrolysis-condensation reaction, the reaction may be performed under conditions where aminosilane is more easily hydrolyzed and condensed, such as using an aqueous solvent containing a catalyst such as alcohol and acetic acid. preferable. Moreover, the hydrolysis condensate with a high condensation degree is obtained by making it react on conditions with a comparatively high aminosilane density | concentration. Specifically, it is preferable to hydrolyze and condense the aminosilane concentration in the range of 5% by mass or more and 50% by mass or less. Incidentally, the degree of condensation ^can be determined by 29 Si-NMR measurement.

  As said polyvinylamine and polyallylamine, what is marketed can be used. Examples of polyvinylamine include “PVAM-0595B” (trade name, manufactured by Mitsubishi Chemical Corporation), and examples of polyallylamine include “PAA-01”, “PAA-10C”, “PAA-H-10C”, “ PAA-D-41HCl "(both trade names, manufactured by Nitto Boseki Co., Ltd.) and the like.

  The molecular weight of the polyamine compound is preferably 150 to 500,000. If it is less than 150, a chemical conversion film having sufficient adhesion may not be obtained. If the molecular weight exceeds 500,000, film formation may be hindered. Further preferred lower and upper limits are 5000 and 70000, respectively. If the amount of amino groups is too large, the polyamine compound may adversely affect the film. If the amount is too small, the effect of improving adhesion to the film due to amino groups is difficult to obtain. It preferably has 1 to 17 mmol of primary and / or secondary amino groups, and preferably has 3 to 15 mmol of primary and / or secondary amino groups per gram of solid content.

  In addition, the number of moles of primary and / or secondary amino groups per 1 g of the solid content of the polyamine compound can be obtained by the following mathematical formula (1).

  (In the formula, when the mass ratio of the solid content of the polyamine compound and the compound having the functional group A and / or the functional group B is m: n, the functionality per 1 g of the compound having the functional group A and / or the functional group B 1 is included per gram of polyamine compound when the number of millimoles of the group A and / or the functional group B is Y and the compound having the functional group A and / or the functional group B is not contained in the metal surface treatment composition. X is the number of millimoles of primary and / or secondary amino groups).

  Content of the said polyamine compound in the metal surface treatment liquid for cationic electrodeposition coating of this invention can be 1 to 200% with respect to the metal conversion mass of the zirconium contained in a surface treatment liquid. If it is less than 1%, the intended effect cannot be obtained, and if it exceeds 200%, a film may not be sufficiently formed. As an upper limit of the content, 120% is more preferable, 100% is more preferable, 80% is further preferable, and 60% is still more preferable.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention may further contain copper ions in order to further improve the corrosion resistance. The amount of the copper ions is preferably a concentration that is 10 to 100% with respect to the concentration of the tin ions. If it is less than 10%, the intended effect may not be obtained, and if the concentration of tin ions is exceeded, zirconium may be difficult to precipitate as in the case of tin ions. Examples of the metal surface treatment liquid for cationic electrodeposition coating of the present invention include a metal surface treatment liquid for cationic electrodeposition coating containing zirconium ions, tin ions and copper ions. In this case, the fluorine ion mentioned later can be contained further and the said polyamine compound can be contained.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention preferably contains fluorine ions. Since the fluorine ion concentration varies depending on the pH, the amount of free fluorine ions at a specific pH is defined. In the present invention, the amount of free fluorine ions when the pH is 3.0 is 0.1 to 50 ppm. If it is less than 0.1 ppm, the metal substrate is not sufficiently etched, so that the amount of coating is reduced and sufficient corrosion resistance cannot be obtained. In addition, the stability of the treatment liquid may not be sufficient. If it exceeds 50 ppm, etching may be excessive and sufficient film formation may not be possible, or the coating amount and film thickness may be uneven, which may adversely affect the appearance of the coating. Preferred lower and upper limits are 0.5 ppm and 10 ppm, respectively. Examples of the metal surface treatment solution for cationic electrodeposition coating of the present invention include a metal surface treatment solution for cationic electrodeposition coating containing zirconium ions, tin ions, and fluorine ions.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention may contain a chelate compound. By including a chelate compound, precipitation of metals other than zirconium in the treatment liquid can be suppressed, and a zirconium oxide film can be stably formed. Examples of the chelate compound include amino acids, aminocarboxylic acids, phenol compounds, aromatic carboxylic acids, sulfonic acids, and ascorbic acids. In addition, the carboxylic acid having a hydroxyl group such as citric acid and gluconic acid, which has been conventionally known as a chelating agent, cannot sufficiently exhibit its function in the present invention.

  As the amino acid, in addition to various natural amino acids and synthetic amino acids, amino acids having at least one amino group and at least one acid group (such as a carboxyl group or a sulfonic acid group) in one molecule can be widely used. Among them, selected from the group consisting of alanine, glycine, glutamic acid, aspartic acid, histidine, phenylalanine, asparagine, arginine, glutamine, cysteine, leucine, lysine, proline, serine, tryptophan, valine, tyrosine, and salts thereof. At least one of the above can be preferably used. In addition, when an amino acid has an optical isomer, any of L-form, D-form, and racemate can be suitably used.

  Moreover, as said aminocarboxylic acid, the compound which has the functional group of both an amino group and a carboxyl group in 1 molecule other than the said amino acid is widely available. Among these, diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetraaminehexaacetic acid (TTHA), 1,3-propanediaminetetraacetic acid (PDTA), 1,3-diamino-6-hydroxy Propane 4 acetic acid (DPTA-OH), hydroxyethyliminodiacetic acid (HIDA), dihydroxyethyl glycine (DHEG), glycol ether diamine tetraacetic acid (GEDTA), dicarboxymethyl glutamic acid (CMGA), (S, S) -ethylenediamine di At least one selected from the group consisting of succinic acid (EDDS), ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and salts thereof can be preferably used.

  Furthermore, examples of the phenol compound include compounds having two or more phenolic hydroxyl groups and phenolic compounds having these as a basic skeleton. Examples of the former include catechol, gallic acid, pyrogallol, tannic acid and the like. On the other hand, examples of the latter include flavonoids such as flavone, isoflavone, flavonol, flavanone, flavanol, anthocyanidin, aurone, chalcone, epigallocatechin gallate, gallocatechin, theaflavin, soybean in, genistin, rutin, myricitrin, tannin, catechin, etc. Examples thereof include polyphenol compounds, polyvinylphenol, water-soluble resols, novolac resins, and lignin. Of these, tannin, gallic acid, catechin and pyrogallol are particularly preferred.

  The sulfonic acid is selected from the group consisting of metasulfonic acid, isethionic acid, taurine, naphthalene disulfonic acid, amino naphthalene disulfonic acid, sulfosalicylic acid, naphthalene sulfonic acid formaldehyde condensate, alkyl naphthalene sulfonic acid, and the like, and salts thereof. At least one of the above can be preferably used.

  When sulfonic acid is used, the paintability and corrosion resistance of the object to be treated after the chemical conversion treatment can be improved. The mechanism is not clear, but there are two possible reasons.

  First of all, the surface of an object to be treated such as a steel plate has a segregated silica, etc., and the surface composition is non-uniform, so there is a portion that is difficult to be etched in chemical conversion treatment. It is presumed that a portion that is difficult to be etched can be particularly etched, and as a result, a uniform metal oxide film is easily formed on the surface of the object to be processed. That is, sulfonic acid is presumed to act as an etching accelerator.

  The other is that during the chemical conversion treatment, hydrogen gas that may be generated by the chemical conversion reaction may interfere with the reaction at the interface, and sulfonic acid removes the hydrogen gas as a depolarizing action and promotes the reaction. Presumed to be.

  Of these, taurine is preferred because it has both an amino group and a sulfone group. As content of a sulfonic acid, 0.1-10000 ppm is preferable and 1-1000 ppm is more preferable. If the content is less than 0.1 ppm, it is difficult to obtain the effect, and if it exceeds 10000 ppm, precipitation of zirconium may be inhibited.

  When ascorbic acid is used, a metal oxide film such as zirconium oxide or tin oxide is uniformly formed on the surface of the object to be processed by chemical conversion treatment, and paintability and corrosion resistance can be improved. Although the mechanism is not clear, the etching action in the chemical conversion treatment is uniformly performed on the workpiece such as a steel plate, and as a result, zirconium oxide and / or tin oxide is precipitated in the etched portion. It is estimated that a uniform metal oxide film is formed as a whole. In addition, as a result of tin being easily precipitated as tin metal at the metal interface due to some influence, it is estimated that zirconium oxide is precipitated at the deposition site of the tin metal, and the surface coverage on the object to be processed is improved as a whole. . As content of ascorbic acid, 5-5000 ppm is preferable and 20-200 ppm is more preferable. If the content is less than 5 ppm, it is difficult to obtain the effect, and if it exceeds 5000 ppm, precipitation of zirconium may be inhibited.

  When the chelating agent is included, the content thereof is preferably 0.5 to 10 times the total concentration of other cations such as tin ions and copper ions other than zirconium. If it is less than 0.5 times, the intended effect cannot be obtained, and if it exceeds 10 times, film formation may be adversely affected.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention can further contain nitrogen, sulfur and / or a phenolic rust inhibitor. The said rust preventive agent can form a corrosion prevention film on the metal surface and can suppress corrosion. As the nitrogen, sulfur, and phenolic rust preventive agent, at least one selected from the group consisting of hydroquinone, ethylene urea, quinolinol, thiourea, benzotriazole, and salts thereof can be used. When nitrogen, sulfur, or phenolic rust inhibitor is used in the metal surface treatment solution for cationic electrodeposition coating of the present invention, the metal oxide film such as zirconium oxide and tin oxide is uniformly formed on the surface of the object to be treated by chemical conversion treatment. The paintability and corrosion resistance can be improved. The mechanism is not clear, but the following is presumed.

  In other words, because the surface of the steel sheet has silica segregation and the surface composition is non-uniform, the chemical film is not formed and the iron oxide is not formed because the etching behavior is different from the part where the chemical film is etched in the chemical conversion treatment. There is a part that becomes a thing. Nitrogen, sulfur, and phenolic rust preventives improve primary rust prevention by adsorbing to the part where the chemical conversion film was not formed during the chemical conversion treatment and covering the metal interface. It is presumed that the paintability and corrosion resistance of the treated product can be improved.

  In addition, when copper is excessively deposited in the chemical conversion film, this copper may become a cathode base point and become an electrically non-uniform chemical conversion film, but a rust inhibitor is added to the excessive copper precipitation site. By making it adsorb | suck, it is estimated that uniform electrodeposition coating property is obtained in the to-be-processed object after chemical conversion treatment, and corrosion resistance can be improved.

  As content of nitrogen, sulfur, and / or a phenol type rust preventive agent, 0.1-10000 ppm is preferable and 1-1000 ppm is more preferable. If the content is less than 0.1 ppm, it is difficult to obtain the effect, and if it exceeds 10000 ppm, precipitation of zirconium may be inhibited.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention may further contain aluminum ions and / or indium ions. Since these cations have the same function as tin ions, they can be used in combination when only the tin ions are not effective. Among these, aluminum is more preferable. The content of aluminum ions and / or indium ions is preferably 10 to 1000 ppm, more preferably 50 to 500 ppm, and still more preferably 100 to 300 ppm. The amount of aluminum ions and indium ions can be set to a concentration corresponding to, for example, 2 to 1000% with respect to the concentration of zirconium ions. Examples of the metal surface treatment liquid for cationic electrodeposition coating of the present invention include a metal surface treatment liquid for cationic electrodeposition coating containing zirconium ions, tin ions, and aluminum ions, and can further contain fluorine described later. Moreover, the polyamine compound mentioned later can be contained.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention may contain various cations in addition to the above components. Examples of the cation include magnesium, zinc, calcium, gallium, iron, manganese, nickel, cobalt, silver and the like. In addition to these, there are cations and anions that are added for the purpose of pH adjustment and are derived from bases and acids, or are included as counter ions of the above components.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention can be produced by introducing the above components themselves and / or a compound containing the same into water and mixing them.

  Examples of the compound supplying the zirconium ion include, for example, fluorinated zirconic acid salts such as fluorinated zirconic acid, potassium fluorinated zirconate and ammonium fluorinated zirconate, zirconium fluoride, zirconium oxide, zirconium oxide colloid, zirconyl nitrate, And zirconium carbonate.

  Examples of the compound that supplies tin ions include tin sulfate, tin acetate, tin fluoride, tin chloride, and tin nitrate. On the other hand, examples of the compound that supplies fluorine ions include fluorides such as hydrofluoric acid, ammonium fluoride, fluorinated boronic acid, ammonium hydrogen fluoride, sodium fluoride, and sodium hydrogen fluoride. It is also possible to use a complex fluoride as a supply source, for example, hexafluorosilicate, specifically, silicofluoric acid, zinc silicofluoride, manganese silicofluoride, silicohydrofluoric acid. Examples thereof include magnesium, nickel silicohydrofluoride, iron silicohydrofluorate, calcium silicohydrofluoride, and the like. Further, it may be a compound that supplies zirconium ions and is a complex fluoride. Furthermore, copper acetate, copper nitrate, copper sulfate, copper chloride, etc. are used as the compounds that supply copper ions, aluminum nitrate, aluminum fluoride, etc. are used as the compounds that supply aluminum ions, and nitric acid is used as the compound that supplies indium ions. Examples thereof include indium and indium chloride.

  The metal surface treatment liquid for cationic electrodeposition coating according to the present invention is prepared by mixing these, and then using an acidic compound such as nitric acid and sulfuric acid, and a basic compound such as sodium hydroxide, potassium hydroxide and ammonia. It can adjust so that it may become pH value of.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention may contain an oxidizing agent. The oxidizing agent is preferably at least one selected from the group consisting of nitric acid, nitrous acid, hydrogen peroxide, bromic acid and the like and salts thereof. The oxidizing agent can uniformly form a metal oxide film on the surface of the object to be processed, and can improve the paintability and corrosion resistance of the object to be processed.

  Although the mechanism is not clear, by using a predetermined amount of the oxidizing agent, the etching action in the chemical conversion treatment is uniformly performed on the workpiece such as a steel plate, and zirconium oxide and / or in the etched portion. It is presumed that tin oxide precipitates to form a uniform metal oxide film as a whole. In addition, the predetermined amount of the oxidizing agent facilitates precipitation of tin as tin metal at the metal interface, and zirconium oxide is deposited at the deposition site of the tin metal, thereby improving the surface coverage of the object as a whole. It is guessed.

  In order to exert such an action, the content of each oxidizing agent is as follows. That is, the nitric acid content is preferably 100 to 100,000 ppm, more preferably 1000 to 20000 ppm, and still more preferably 2000 to 10,000 ppm. As content of nitrous acid and bromic acid, 5-5000 ppm is preferable and 20-200 ppm is more preferable. As content of nitrous acid and bromic acid, 5-5000 ppm is preferable and 20-200 ppm is more preferable. As content of hydrogen peroxide, 1-1000 ppm is preferable and 5-100 ppm is more preferable. When each content is less than the lower limit, the above effect is hardly obtained, and when the content exceeds the upper limit, precipitation of zirconium may be hindered.

  The metal surface treatment method of the present invention includes a step of performing a surface treatment on a metal substrate using the previous metal surface treatment liquid.

  The metal substrate is not particularly limited as long as it can be cationically electrodeposited. Examples thereof include iron-based metal substrates, aluminum-based metal substrates, and zinc-based metal substrates. it can.

  Examples of the iron-based metal base material include a cold-rolled steel plate, a hot-rolled steel plate, a mild steel plate, and a high-tensile steel plate. Examples of the aluminum-based metal base material include a 5000-series aluminum alloy, a 6000-series aluminum alloy, aluminum-plated steel sheets such as aluminum-based electroplating, hot dipping, and vapor deposition plating. In addition, as the zinc-based metal substrate, for example, zinc-based electroplating such as galvanized steel sheet, zinc-nickel plated steel sheet, zinc-titanium plated steel sheet, zinc-magnesium plated steel sheet, zinc-manganese plated steel sheet, hot dipping, Examples include zinc or zinc-based alloy-plated steel sheets such as vapor-deposited steel sheets. The high-strength steel sheet has various grades depending on strength and manufacturing method, and examples thereof include JSC400J, JSC440P, JSC440W, JSC590R, JSC590T, JSC590Y, JSC780T, JSC780Y, JSC980Y, and JSC1180Y.

  Moreover, it applies simultaneously also to the metal base material which consists of a combination (including the junction part and contact part of dissimilar metals) of multiple types, such as iron type, aluminum type, and zinc type, as said metal base material. be able to.

  The surface treatment step is performed by bringing the metal surface treatment liquid into contact with the metal substrate. Specific examples of the method include a dipping method, a spray method, a roll coating method, and a pouring treatment method.

  The treatment temperature in the surface treatment step is preferably in the range of 20 to 70 ° C. If it is less than 20 degreeC, sufficient film formation may not be performed, and even if it exceeds 70 degreeC, the effect corresponding to it cannot be expected. Furthermore, a preferable lower limit and upper limit are 30 degreeC and 50 degreeC, respectively.

  The treatment time in the surface treatment step is preferably 2 to 1100 seconds. If it is less than 2 seconds, there is a possibility that a sufficient amount of film cannot be obtained, and even if it exceeds 1100 seconds, an effect commensurate with it cannot be expected. Further preferred lower and upper limit values are 30 seconds and 120 seconds, respectively. In this way, a film is formed on the metal substrate.

  The surface-treated metal substrate of the present invention is obtained by the previous surface treatment method. A film containing zirconium and copper is formed on the surface of the metal substrate. The zirconium / tin element ratio in the coating is preferably 1/10 to 10/1 in terms of mass. Outside this range, the target performance may not be obtained.

In the case of an iron-based metal base material, the zirconium content in the coating is preferably 10 mg / m ² or more. If it is less than 10 mg / m ² , sufficient anticorrosive properties cannot be obtained. More preferably, it is 20 mg / m ² or more, and further preferably 30 mg / m ² or more. The upper limit is not particularly defined, but if the amount of the film is too large, cracks are likely to occur in the rust-proof film, making it difficult to obtain a uniform film. In this respect, the zirconium content in the film is preferably 1 g / m ² or less, and more preferably 800 mg / m ² or less.

When the film is formed using a metal surface treatment liquid containing copper ions, the copper content in the film is preferably 0.5 mg / m ² or more in order to obtain the intended effect. .

  The cationic electrodeposition coating method of the present invention includes a step of performing a surface treatment on a metal substrate using the previous metal surface treatment solution, and a cationic electrodeposition coating on the metal substrate subjected to the surface treatment. The process of performing.

  The surface treatment step in the cationic electrodeposition coating method is the same as the surface treatment step in the previous surface treatment method. The surface-treated metal substrate obtained in the surface treatment step enters the cationic electrodeposition coating step as it is or after washing.

  In the cationic electrodeposition coating step, cationic electrodeposition coating is performed on the metal base material that has been surface-treated. In the cationic electrodeposition coating, a metal substrate subjected to the above surface treatment is immersed in a cationic electrodeposition coating, and a voltage of 50 to 450 V is applied for a predetermined time using this as a cathode. The voltage application time varies depending on the electrodeposition conditions, but is generally 2 to 4 minutes.

  As the cationic electrodeposition coating, generally well-known ones can be used. Specifically, binders cationized by adding amines or sulfides to epoxy groups of epoxy resins and acrylic resins, and adding neutralizing acids such as acetic acid, blocked isocyanates as curing agents, and rust prevention In general, a pigment dispersion paste obtained by dispersing a pigment having a pigment with a resin is added to form a paint.

After completion of the cationic electrodeposition coating process, a cured coating film is obtained by baking at a predetermined temperature as it is or after washing with water. Although baking conditions change with kinds of used cationic electrodeposition coating material, they are 120-260 degreeC normally, and it is preferable that it is 140-220 degreeC. The baking time can be 10 to 30 minutes.
The metal substrate coated with cationic electrodeposition obtained in this way is also one aspect of the present invention.

Production Example 1 Production of Hydrolyzed Condensate of Aminosilane Part 1
As aminosilane, KBE603 (3-aminopropyl-triethoxysilane, effective concentration 100%, manufactured by Shin-Etsu Chemical Co., Ltd.), 5 parts by mass of 47.5 parts by mass of deionized water and 47.5 parts by mass of isopropyl alcohol from the dropping funnel After dropping uniformly into the mixed solvent (solvent temperature: 25 ° C.) over 60 minutes, the reaction was performed at 25 ° C. for 24 hours in a nitrogen atmosphere. Thereafter, the reaction solution was depressurized to evaporate isopropyl alcohol, and deionized water was further added to obtain a hydrolysis-condensation product of aminosilane having an active ingredient of 5%.

Production Example 2 Production of Aminosilane Hydrolysis Condensate Part 2
In Production Example 1, except that the amount of KBE603 is changed to 20 parts by mass, the amount of deionized water is changed to 40 parts by mass, and the amount of isopropyl alcohol is changed to 40 parts by mass, A hydrolysis condensate was obtained.

Example 1
After mixing 40% zirconic acid aqueous solution as a zirconium ion supply source, tin sulfate as a tin ion supply source, and hydrofluoric acid, this was diluted to a zirconium ion concentration of 500 ppm and a tin ion concentration of 30 ppm. In addition, the pH was adjusted to 3.5 using nitric acid and sodium hydroxide to obtain a metal surface treatment solution for cationic electrodeposition coating. In addition, after adjusting this process liquid to pH3.0, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was 5 ppm.

Example 2
In Example 1, the aminosilane hydrolysis condensate obtained in Production Example 1 was further added to 200 ppm, and tin sulfate was changed to tin acetate to change the tin ion concentration to 10 ppm. A metal surface treatment solution for cationic electrodeposition coating was obtained in the same manner except that the pH was 2.75. In addition, after adjusting this process liquid to pH3.0, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was 5 ppm.

Example 3
In Example 1, polyallylamine “PAA-H-10C” (trade name, manufactured by Nitto Boseki Co., Ltd.) was added to 25 ppm, the zirconium ion concentration was changed to 250 ppm, and the pH was further adjusted to 3 A metal surface treatment solution for cationic electrodeposition coating was obtained in the same manner except that it was set to 0.0. In addition, about this process liquid, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was 5 ppm.

Example 4
In Example 1, copper nitrate was further added so that the copper ion concentration was 10 ppm, and the tin ion concentration was changed to 10 ppm. A metal surface treatment solution for electrodeposition coating was obtained. In addition, about this process liquid, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was 5 ppm.

Example 5
Cationic electrodeposition coating was performed in the same manner as in Example 4, except that the aminosilane hydrolysis condensate obtained in Production Example 2 was added to 200 ppm, and the tin ion concentration was changed to 30 ppm. A metal surface treatment solution was obtained. In addition, about this process liquid, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was 5 ppm.

Example 6
In the same manner as in Example 2, except that aluminum nitrate was further added to have an aluminum ion concentration of 200 ppm, and tin sulfate was changed to tin acetate to change the tin ion concentration to 30 ppm. A metal surface treatment solution for electrodeposition coating was obtained. In addition, after adjusting this process liquid to pH3.0, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was 5 ppm.

Examples 7 and 8
A metal surface treatment solution for cationic electrodeposition coating was obtained in the same manner as in Example 6 except that the pH was 3.5 and 4.0. In addition, after adjusting this process liquid to pH3.0, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was shown in Table 1.

Examples 9-16
In Example 7, the same procedure was performed except that the addition amounts of 40% aqueous zirconate solution, tin sulfate, and aluminum nitrate were changed so that the zirconium ion concentration, tin ion concentration, and aluminum ion concentration became the concentrations shown in Table 1. Thus, a metal surface treatment solution for cationic electrodeposition coating was obtained. In addition, after adjusting this process liquid to pH3.0, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was shown in Table 1.

Example 17
In Example 2, indium nitrate was further added to have an indium ion concentration of 200 ppm, and tin sulfate was changed to tin fluoride so that the tin ion concentration was 30 ppm. Further, the pH was set to 3.5. A metal surface treatment solution for cationic electrodeposition coating was obtained in the same manner except that. In addition, after adjusting this process liquid to pH3.0, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was 5 ppm.

Example 18
In Example 2, diethylenetriaminepentaacetic acid (DTPA) was further added as a chelating agent so as to have a concentration of 100 ppm, and tin acetate was changed to tin sulfate so that the tin ion concentration became 30 ppm. A metal surface treatment solution for cationic electrodeposition coating was obtained in the same manner except that the concentration was changed to 1000 ppm. In addition, after adjusting this process liquid to pH3.0, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was 10 ppm.

Example 19
In Example 2, sodium nitrate was further added so that the sodium ion concentration became 5000 ppm, and the metal surface treatment solution for cationic electrodeposition coating was obtained in the same manner except that the tin ion concentration was changed to 30 ppm. It was. In addition, after adjusting this process liquid to pH3.0, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was 5 ppm.

Example 20
In Example 5, glycine and copper nitrate as chelating agents were further added to a concentration of 50 ppm and a copper ion concentration of 10 ppm, respectively, and the polyamine concentration was changed to 100 ppm. A metal surface treatment solution for electrodeposition coating was obtained. In addition, about this process liquid, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was 5 ppm.

Examples 21-31
In Example 1, a metal surface treatment solution for cationic electrodeposition coating was prepared in the same manner except that a predetermined amount of the polyamine described in Table 1 was added and the concentrations of other components were changed as described in Table 1. I got each. In addition, about these process liquids, the free fluorine ion density | concentration at the time of measuring using a fluorine ion meter on the conditions of pH3.0 is collectively shown in Table 1.

Examples 32-50
A metal surface treatment solution for cationic electrodeposition coating was obtained in the same manner as in Example 1 except that a predetermined amount of the sulfonic acid described in Table 2 was added and the polyamine and other components were changed as shown in Table 2. In addition, about these process liquids, the free fluorine ion density | concentration at the time of measuring using a fluorine ion meter on the conditions of pH3.0 is collectively shown in Table 2.
In Table 2, the Naphthalenesulfonic acid-formaldehyde condensate used was Kao-made Demol NL, Sodium Alkylnaphthalenesulfonate was used as Kao-Perex NBL, and Sodium Polystyrenesulfonate was used as Tosoh P-NASS-1.

Example 51
A metal surface treatment solution for cationic electrodeposition coating was obtained in the same manner as in Example 1 except that a predetermined amount of ascorbic acid described in Table 3 was added and polyamine and other components were changed as shown in Table 3. In addition, about these process liquids, the free fluorine ion density | concentration at the time of measuring using a fluorine ion meter on the conditions of pH3.0 is collectively shown in Table 3.

Examples 52-59
A metal surface treatment solution for cationic electrodeposition coating was obtained in the same manner as in Example 1 except that a predetermined amount of the oxidizing agent described in Table 3 was added and that the polyamine and other components were as shown in Table 3. In addition, about these process liquids, the free fluorine ion density | concentration at the time of measuring using a fluorine ion meter on the conditions of pH3.0 is collectively shown in Table 3.

Examples 60-74
In Example 1, the nitrogen-based rust inhibitor, sulfur-based rust preventive agent, and phenol-based rust preventive agent described in Table 3 were added in predetermined amounts, and the polyamine and other components were as shown in Table 3 except that they were as shown in Table 3. In the same manner as in No. 1, metal surface treatment solutions for cationic electrodeposition coating were obtained. In addition, about these process liquids, the free fluorine ion density | concentration at the time of measuring using a fluorine ion meter on the conditions of pH3.0 is collectively shown in Table 3.

Examples 75-77
The substrate to be treated was a high-tensile steel plate instead of a cold-rolled steel plate (SPC), and the same procedure as in Example 1 was repeated except that the polyamine and other components listed in Table 3 were as shown in Table 2. Each metal surface treatment solution for electrodeposition coating was obtained. In addition, about these process liquids, the free fluorine ion density | concentration at the time of measuring using a fluorine ion meter on the conditions of pH3.0 is collectively shown in Table 3.

Examples 78-106
About Example 2, 3, and 5-31, except having added no polyamine, it carried out similarly to each Example, and obtained the metal surface treatment liquid for cationic electrodeposition coating. In addition, after adjusting this process liquid to pH3.0, the free fluorine ion concentration at the time of measuring using a fluorine ion meter was shown in Table 4.

Comparative Examples 1-6 Preparation of Comparative Metal Surface Treatment Liquid Based on the descriptions in Tables 1 and 3, comparative metal surface treatment liquids were obtained based on the above examples. The obtained metal surface treatment liquids are summarized in Tables 1 and 3.

<Surface treatment>
In Examples 1 to 74, Examples 78 to 106, and Comparative Examples 1 to 5, a commercially available cold-rolled steel sheet (SPC, 70 mm × 150 mm × 0.8 mm, manufactured by Nippon Test Panel Co., Ltd.) was prepared and implemented as a metal substrate. In Examples 75 to 77 and Comparative Example 6, a high-tensile steel plate (70 mm × 150 mm × 1.0 mm) is prepared, and “Surf Cleaner EC92” (trade name, manufactured by Nippon Paint Co., Ltd.) is used as an alkaline degreasing agent. The degreasing treatment was performed at 40 ° C. for 2 minutes. This was immersed and washed in a water washing tank, and then spray washed with tap water for about 30 seconds.

  The surface treatment was performed by immersing the metal substrate after degreasing treatment in the metal surface treatment solution prepared in Examples and Comparative Examples at 40 ° C. for 90 seconds. However, for Examples 21 and 22, the processing time was 240 seconds and 15 seconds, respectively. After completion of the surface treatment, drying was performed at 40 ° C. for 5 minutes or more to obtain a surface-treated metal substrate. Unless otherwise specified, in the following evaluation, this surface-treated metal substrate was used as a test plate.

<Measurement of element content in film>
The content of each element contained in the film was measured using a fluorescent X-ray analyzer “XRF1700” manufactured by Shimadzu Corporation.

  <Primary rust prevention>

The state of rust generation after immersing the test plate in pure water at 25 ° C. for 5 hours was observed by visual observation.
○: Rust is not observed at all △: Slight rust is generated ×: Rust is clearly confirmed

<Observation of sludge>
With respect to the surface treatment liquid 10L of the examples and comparative examples, 200 test panels were surface-treated, and when 30 days passed at room temperature, whether or not turbidity due to the generation of sludge occurred in the surface treatment liquid was visually determined as follows. Evaluation based on the criteria.
◎: Transparent liquid ○: Slightly turbid △: Turbid ×: Precipitate (sludge) generated

<Evaluation of throwing power>
The throwing power was evaluated by the “four-sheet box method” described in Japanese Patent Application Laid-Open No. 2000-038525. That is, as shown in FIG. 1, a box 10 was prepared in which test plates 1 to 4 were erected and arranged in parallel at an interval of 20 mm, and the lower and bottom surfaces of both sides were sealed with an insulator such as cloth adhesive tape. The metal materials 1, 2, and 3 excluding the metal material 4 were provided with through holes 5 having a diameter of 8 mm in the lower part.

  This box 10 was immersed in an electrodeposition coating container 20 filled with a cationic electrodeposition paint “Powernics 110” (trade name, manufactured by Nippon Paint Co., Ltd.). In this case, the cationic electrodeposition paint penetrates into the inside of the box 10 only from each through hole 5.

  While stirring the cationic electrodeposition paint with a magnetic stirrer, the test plates 1 to 4 were electrically connected, and the counter electrode 21 was arranged so that the distance from the test plate 1 was 150 mm. A voltage was applied using each test plate 1 to 4 as a cathode and the counter electrode 21 as an anode, and cation electrodeposition coating was performed. The coating was performed by increasing the voltage to the target voltage (210 V and 160 V) over 30 seconds from the start of application, and then maintaining that voltage for 150 seconds. The bath temperature at this time was adjusted to 30 ° C.

  Each of the test plates 1 to 4 after painting was washed with water, baked at 170 ° C. for 25 minutes, then air-cooled, and the film thickness of the coating film formed on the A surface of the test plate 1 closest to the counter electrode 21; The film thickness of the coating film formed on the G surface of the test plate 4 farthest from the counter electrode 21 is measured, and the throwing power is evaluated by determining the ratio of film thickness (G surface) / film thickness (A surface). did. It can be evaluated that the larger the value, the better the throwing power. The passing level is 40% or more.

<Paint voltage>
Using the surface treatment liquids of Examples and Comparative Examples, surface treatment was performed on cold-rolled steel sheets and galvanized steel sheets to obtain test plates. With respect to these test plates, using the cationic electrodeposition paint “Powernics 110”, a voltage necessary for obtaining a 20 μm electrodeposition coating film was obtained. The difference of the coating voltage required in order to obtain the said electrodeposition coating film of 20 micrometers in the case where a metal base material is a galvanized steel plate and the case of a cold-rolled steel plate was calculated | required. The smaller the difference, the better the surface treatment film. 40V or less is acceptable.

  In addition, the voltage required in order to obtain a 20 micrometer electrodeposition coating film was calculated | required as follows. That is, as the electrodeposition conditions, the voltage is increased to a predetermined voltage in 30 seconds, and then held for 150 seconds, and the obtained film thickness is measured. This is performed for 150V, 200V, and 250V, and a voltage at which a film thickness of 20 μm is obtained is obtained from the relational expression between the obtained voltage and the film thickness.

<Paint appearance>
Cationic electrodeposition coating was performed on the test plate, and the appearance of the obtained electrodeposition coating film was evaluated according to the following criteria. The results are shown in Tables 5-8.
◎: Uniform coating film is obtained ○: Almost uniform coating film is obtained △: The coating film is slightly uneven ×: Unevenness is observed in the coating film

<Secondary adhesion test (SDT)>
After forming a 20 μm electrodeposition coating film on the test plate, two longitudinally parallel cuts reaching the metal substrate were put and immersed in a 5% aqueous sodium chloride solution at 55 ° C. for 240 hours. Next, after washing with water and air drying, the adhesive tape “ELPACK LP-24” (trade name, manufactured by Nichiban Co., Ltd.) was adhered to the cut part, and then the adhesive tape was peeled off rapidly. The size of the maximum width (one side) of the paint adhering to the peeled adhesive tape was measured.
A: 0 mm
○: Less than 2 mm Δ: 2 mm or more and less than 5 mm ×: 5 mm or more

<Cycle corrosion test (CCT)>
After forming an electrodeposition coating film having a thickness of 20 μm on the test plate, the edges and the back surface were tape-sealed, and a cross-cut flaw reaching the metal substrate was put. This was continuously sprayed for 2 hours with a 5% sodium chloride aqueous solution kept at 35 ° C. in a salt spray tester maintained at 35 ° C. and humidity 95%. Subsequently, it dried for 4 hours on the conditions of 60 degreeC and humidity 20-30%. This was repeated three times over 24 hours to make one cycle, and the swelling width (both sides) of the coating film was measured after 200 cycles.
◎: Less than 6 mm ○: 6 mm or more and less than 8 mm △: 8 mm or more and less than 10 mm ×: 10 mm or more

<Salt spray test (SST)>
After forming an electrodeposition coating film having a thickness of 20 μm on the test plate, the edges and the back surface were tape-sealed, and a cross-cut flaw reaching the metal substrate was put. This was continuously sprayed with a 5% sodium chloride aqueous solution kept at 35 ° C. for 840 hours in a salt spray tester kept at 35 ° C. and 95% humidity. Next, after washing with water and air drying, the adhesive tape “ELPACK LP-24” (trade name, manufactured by Nichiban Co., Ltd.) was adhered to the cut part, and then the adhesive tape was peeled off rapidly. The size of the maximum width (one side) of the paint adhering to the peeled adhesive tape was measured.
○: Less than 2 mm Δ: 2 mm or more and less than 5 mm ×: 5 mm or more

  The evaluation results are summarized in Tables 5-8.

  The metal surface treatment liquid for cationic electrodeposition coating of the present invention can be applied to a metal substrate to which cationic electrodeposition is applied, for example, an automobile body or a part.

It is a perspective view which shows an example of the box used when evaluating throwing power. It is drawing which shows typically evaluation of throwing power.

Explanation of symbols

  1, 2, 3, 4 ... test plate, 5 ... through hole, 10 ... box, 20 ... electrodeposition coating container, 21 ... counter electrode

Claims (10)

A step of performing a surface treatment on the iron-based metal substrate using a metal surface treatment liquid, a step of washing the metal substrate on which the surface treatment has been performed, and a cationic electrode on the washed metal substrate. A method of cationic electrodeposition coating, including a step of performing coating.
The metal surface treatment liquid is
Zirconium ions, and a tin ion, Ri metal surface treatment liquid der the pH is 1.5 to 6.5,
The concentration of the zirconium ions is 10 to 10000 ppm, and
The concentration ratio of tin ions to zirconium ions is 0.005 to 1 in terms of mass.
Cationic electrodeposition coating method . The cationic electrodeposition coating method according to claim 1, wherein the metal surface treatment liquid further contains a polyamine compound. The cationic electrodeposition coating method according to claim 1, wherein the metal surface treatment liquid further contains copper ions. The cationic electrodeposition coating according to any one of claims 1 to 3, wherein the metal surface treatment liquid further contains fluorine ions and has a free fluorine ion amount of 0.1 to 50 ppm when the pH is 3.0. Way . The cationic electrodeposition coating method according to claim 1, wherein the metal surface treatment liquid further contains a chelate compound. 6. The cationic electrodeposition coating method according to claim 5, wherein the chelate compound is sulfonic acid. The cationic electrodeposition coating method according to claim 1, wherein the metal surface treatment liquid further contains an oxidizing agent. The metal surface treatment solution, further to containing aluminum ions and / or indium ions, cationic electrodeposition coating process according to any one of claims 1 to 7. A metal substrate coated with cationic electrodeposition, obtained by the method according to claim 1. The metal substrate coated with cationic electrodeposition according to claim 9, wherein the element ratio of zirconium / tin in the film formed by the surface treatment is 1/10 to 10/1 in terms of mass.

Images