Technical field
[0001]
　The present invention relates to a Zn-Mg alloy plated steel sheet.
　The present application, on April 7, 2015, claiming priority based on Japanese Patent Application No. 2015-78585 filed in Japan, the contents of which are incorporated here.
Background technique
[0002]
　Automobiles, home appliances, the steel used in building materials, sometimes are plated in order to improve the corrosion resistance. The plating layer formed on the steel surface by plating, a barrier anticorrosive plating layer type shielding base steel (the steel) from the external environment, sacrificial protection plating layer type of corrosion to the base steel by preferentially corroded than the iron metal It is roughly classified into two types of. Although Zn is used for plating steel conventionally plated layer formed by Zn plating is classified into sacrificial plating layer type.
[0003]
　Steel sheet plated layer is formed on a surface (hereinafter, plated steel sheet and referred) when using a long period of time, coating treatment on the surface of the plated steel sheet (i.e., the surface of the plating layer), chemical treatment, or lamination etc. by surface treatment of, improving the rust resistance. Chemical treatment, mainly, an object of surface improvement of the primary rust-preventive to rust the coated steel sheet until the plated steel sheet is processed and assembled to the final product. The chemical conversion treatment, a layer having a surface with a suitable adhesion of the plating layer (hereinafter, referred to as chemical conversion treatment layer) is formed on the surface of the plating layer.
[0004]
　As shown in Patent Documents 1-4, in recent years, in order to improve the corrosion resistance, instead of Zn-plated steel sheet, Zn-Mg alloy plated layer containing Zn-Mg alloy is formed on the surface of the steel sheet plated steel sheet has been proposed. Zn-Mg alloy plated steel sheet, by stabilizing the corrosion product formed in a corrosive environment by Mg, it has excellent corrosion resistance than Zn-plated steel sheet.
CITATION
Patent Literature
[0005]
Patent Document 1: Japanese Laid-Open Patent Publication No. 2005-146340
Patent Document 2: Japanese Laid-Open Patent Publication No. 2007-23309
Patent Document 3: Japanese Laid-Open Patent Publication No. 2010-248541
Patent Document 4: Japanese Patent Laid-Open 2011-219823 Bulletin No.
Summary of the Invention
Problems that the Invention is to Solve
[0006]
　As described above, Zn-Mg alloy plated steel sheet has excellent corrosion resistance as compared with the Zn-plated steel sheet. However, with respect to Zn-Mg alloy plated steel sheet, when subjected to chemical conversion treatment to be used in Zn plated steel sheet, if the Zn-Mg alloy plated steel sheet is discolored black (hereinafter, referred to as blackening phenomenon) and, chemical conversion treatment If blistering layer is formed (hereinafter, referred to as blister formation phenomenon) has, may not be obtained a suitable primary rust resistance.
　Incidentally, blackening phenomenon, Mg ions eluted from the plating layer is caused to form a stoichiometric oxide, blister formation phenomenon generates unstable corrosion Mg ions eluted from the plating layer is continuously It believed to be due to the formation of things.
[0007]
　The present invention has been made in view of the above circumstances and has an excellent primary rust resistance, and to provide a Zn-Mg alloy plated steel sheet having a chemical conversion layer.
Means for Solving the Problems
[0008]
　The present inventors have found that by forming a stable corrosion products by Mg ions eluted from Zn-Mg alloy was investigated a method for improving the primary rust resistance. As a result, the present inventors have found that small solubility of Mg salts, by incorporating the chemical conversion treatment layer a solubility greater substance of an alkali metal salt, and Mg eluted from the plating layer in a corrosive environment, the chemical conversion treatment layer and eluted material is bonded, corrosion portion of the plating layer is covered by the formed stable corrosion products were found that could suppress the blackening phenomenon and blisters formation phenomena.
[0009]
　Further, the present inventors have further advanced the study, containing an alkali metal salt of an alkane sulfonic acid alkali metal salt or the carbon number of the carboxylic acid carbon number of 4-20 is 4-20 chemical conversion treatment layer by, it found that primary corrosion resistance of Zn-Mg alloy plated steel sheet is remarkably improved, and have completed the present invention.
　The present invention is to solve the above problems, adopts the following means in order to achieve the object
[0010]
(1) Zn-Mg alloy plated steel sheet according to one embodiment of the present invention includes a steel plate, is formed on the surface of the steel sheet, containing Mg 1.0 to 70.0%, the balance being Zn and impurities and Zn-Mg alloy plating layer containing, formed on the surface of the Zn-Mg alloy plating layer, Mg salts of alkanesulfonic acid Mg salt and the carbon number of the carboxylic acid carbon number of 4-20 is 4-20 a corrosion product layer containing either one of the, formed on the surface of the corrosion product layer, an alkali metal salt of the carboxylic acid in the case of the corrosion product layer comprises a Mg salt of the carboxylic acid containing, said corrosion product layer and a chemical conversion layer containing an alkali metal salt of the alkanoic acid in the case of containing Mg salt of the alkane sulfonic acids, contained in the chemical conversion treatment layer of the carboxylic acid Al Alkali metal Li metal salts or alkali metal salts of the alkanesulfonic acid is at least one of Li, Na, K, selected from the group consisting of Rb and Cs.
[0011]
(2) In Zn-Mg alloy plated steel sheet according to (1), the Zn-Mg alloy plating layer, may be adopted containing 5.0 to 70.0% by weight of Mg.
[0012]
(3) In Zn-Mg alloy plated steel sheet according to (2), the Zn-Mg alloy plating layer, may be adopted containing 10.0 to 70.0% by weight of Mg.
[0013]
(4) In Zn-Mg alloy plated steel sheet according to (3), the Zn-Mg alloy plating layer, may be adopted including a Mg of 15.0 to 70.0 wt%.
[0014]
In Zn-Mg alloy plated steel sheet according to any one aspect of (5) above (1) to (4), the Zn-Mg alloy plating layer, and 0.3 to 25.0 wt% Al, 0 .01 and to 5.00 mass% of Si, and 1.0 to 5.0 mass% Ca, and Ni of 0.1 to 1.5 mass%, at least one selected from the group consisting of further the may be adopted configured to include.
[0015]
(6) In Zn-Mg alloy plated steel sheet according to any one aspect of the above (1) to (5), wherein the alkali metal is, may be adopted is Na.
[0016]
(7) In Zn-Mg alloy plated steel sheet according to (6), the content of the alkali metal salt of an alkali metal salt or the alkanesulfonic acid of the carboxylic acid contained in the chemical conversion treatment layer, in terms of Na Te 10 ~ 1500 mg / m 2 is a configuration may be employed.
[0017]
(8) In Zn-Mg alloy plated steel sheet according to any one aspect of the above (1) to (7), the carbon number of the carboxylic acid or the alkanesulfonic acid, employs a configuration which is 5-20 it may be.
[0018]
(9) In Zn-Mg alloy plated steel sheet according to (8), the carbon number of the carboxylic acid or the alkanesulfonic acids, may be adopted which is 8-12.
[0019]
(10) In Zn-Mg alloy plated steel sheet according to any one aspect of the above (1) to (9), the carboxylic acid may be employed a configuration which is a saturated fatty acid.
[0020]
(11) In Zn-Mg alloy plated steel sheet according to any one aspect of the above (1) to (10), wherein the chemical conversion treatment layer, a fluoride, be adopted a structure which does not contain trivalent chromium and vanadium good.
Effect of the invention
[0021]
　According to the above embodiment, it is possible to provide a Zn-Mg alloy plated steel sheet having a superior with primary rust resistance, chemical conversion treatment layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022]
FIG. 1 is a schematic diagram showing a layer structure of Zn-Mg alloy plated steel sheet according to the present embodiment.
DESCRIPTION OF THE INVENTION
[0023]
　Hereinafter, a Zn-Mg alloy plated steel sheet and a manufacturing method according to the embodiment will be described with reference to the drawings.
(Zn-Mg alloy plated steel sheet 1)
　FIG. 1 is a schematic view showing the layer structure of a Zn-Mg alloy plated steel sheet 1. Zn-Mg alloy plated steel sheet 1, a steel plate 2, are formed on the surface of the steel plate 2, containing 10 to 70 wt% of Mg, and Zn-Mg alloy plating layer 3 balance containing Zn and impurities, Zn- formed on the surface of the Mg alloy plating layer 3, the corrosion product containing one of the Mg salt of alkanesulfonic acid Mg salt and the carbon number of the carboxylic acid carbon number of 4-20 is 4-20 a layer 4 formed on the surface of the corrosion product layer 4, if the corrosion product layer 4 contains Mg salt of a carboxylic acid containing an alkali metal salt of a carboxylic acid, the corrosion product layer 4 alkanesulphonic comprises, a chemical conversion treatment layer 5 containing the alkali metal salt of an alkane sulfonic acid in the case of containing Mg salt of the acid.
　Conventional Zn-Mg alloy plated steel sheet 1, blackening phenomenon and swelling formation phenomenon is remarkable when forming a chemical conversion layer 5 on the Zn-Mg alloy plating layer 3. However, Zn-Mg alloy plated steel sheet 1 according to this embodiment, even if to form a chemical conversion layer 5, by inhibiting the formation of stoichiometric oxide or unstable corrosion products Mg, the primary corrosion resistance is significantly improved.
[0024]
　Although details will be described later, by containing the alkali metal salt of a carboxylic acid or an alkane sulfonic acid having a carbon number of 4 to 20 chemical conversion layer 5, a primary rust-preventive effect of improving the above can be obtained. And Mg ions eluted from Zn-Mg alloy plating layer 3 under the chemical conversion treatment step and corrosive environment, combines the eluted carboxylate ion or an alkane sulfonate ion from the chemical conversion treatment layer 5, a stable corrosion product carboxylic Mg salts or Mg salts of alkanesulfonic acids of acid is produced. Mg salt of Mg salt or alkanesulfonic acids of the generated carboxylic acid, precipitated in layers on Zn-Mg alloy plating layer 3 to form a corrosion product layer 4. Carboxylic acid or an alkane sulfonic acid having a carbon number of 4 to 20 the Mg salt is formed by binding to Mg, in particular covering the corrosion portion. As a result, elution of Mg ions from the Zn-Mg alloy plating layer 3 is suppressed.
[0025]
Zn-Mg alloy plating layer 3 contains a Zn-Mg alloy, optionally, Al, Si, contains at least one element selected from the group consisting of Ca and Ni it may be. Furthermore, Y, La, Ce, Ti , Cr, Fe, Co, V, Nb, Cu, Sn, Mn, Sr, Sb, an element such as Pb may contain about 0 to 5 mass%.
　In the following, Mg, Al, Si, Ca , the content of Ni is explained. Incidentally, the remainder other than these alloy elements, including Zn and impurities. Here, the impurity is a component to be mixed by various factors of the raw material and manufacturing process, a so-called unavoidable impurities. Balance other than the above alloy elements is preferably made of Zn and unavoidable impurities.
[0026]
Mg (magnesium) is a major element constituting a Zn-Mg alloy plating layer 3 with Zn. The content of Mg in Zn-Mg alloy plating layer 3, in order to improve the sacrificial corrosion resistance, and 1.0 mass% or more. Preferably the content of Mg 5 mass% or more, more preferably 10 mass% or more, further preferably 15 mass% or more. On the other hand, when the content of Mg exceeds 70.0 wt%, out Mg phase crystallizes in Zn-Mg alloy plating layer 3, since the corrosion resistance drastically deteriorates.
　As described below, Mg of Zn-Mg alloy plating layer 3 generates a Mg salt reacts with a carboxylic acid or an alkane sulfonic acid is applied to the surface. The Mg salt has a corrosion resistance of the Zn-Mg alloy layer 3 than when Mg salt is not, thereby further improving action. For corrosion resistance further improves the above preferred Mg concentration is for this reason, simply the effect of the above corrosion resistance obtained by increasing the Mg concentration (Tanaka postscript).
　When the Zn-Mg alloy plating layer 3 does not contain Mg, since the Mg salts described carboxylic acid or an alkane sulfonic acid is not formed, the corrosion product layer 4 is not formed. Therefore, since the preferred corrosion resistance can not be obtained, which is not preferable.
[0027]
Al is an element that improves the corrosion resistance of the flat portion of the Zn-Mg alloy plating layer 3. In order to obtain this effect, it is preferable to contain a Zn-Mg alloy plating layer 3 0.30 mass% or more Al. On the other hand, when the content of Al is more than 25.0 wt%, since it is possible to decrease the corrosion resistance tends red rust occurs, it is preferable to 25.0% by mass or less the upper limit. Considering the adhesion of the chemical conversion layer 5 with respect to Zn-Mg alloy plating layer 3, the content of Al is more preferably 20.0 mass% or less.
[0028]
Si serves to inhibit the growth of the alloy phase formed at the interface between the steel plate 2 and the Zn-Mg alloy plating layer 3, to prevent deterioration of workability element , and the it is preferably contained in the Zn-Mg alloy plating layer 3 or 0.010 wt%. When the content of Si exceeds 5.0 mass%, the bottom dross in the plating bath becomes tends to be formed, because the workability is lowered, less preferably 5.0 wt%.
[0029]
Ca, in order to improve the workability of hot-dipping, is added to the Zn-Mg alloy plating layer 3 as required. When manufacturing a Zn-Mg alloy plated steel sheet 1 according to this embodiment uses a Mg-containing alloy as the plating bath. For Mg-containing alloy in a molten state to form a suitable oxide film on the surface, it is preferable to add a Ca is an element effective in preventing oxidation of Mg 1.0% by mass or more. Ca, since it may deteriorate the corrosion resistance in many cases the content, it is preferable that the upper limit of the content of Ca in the Zn-Mg alloy plating layer 3 and 5.0 wt%.
[0030]
Ni is an element for improving the wettability of the plating. Interface the pre-formed steel plate 2 plated with Zn-Mg alloy plating layer 3 of Ni, than the case of forming a Zn-Mg alloy plating layer 3 on the steel plate 2, the steel plate 2 and the Zn-Mg alloy plating layer 3 formation of Al-Fe intermetallic compound in the vicinity is suppressed, thereby improving the workability. On the other hand, when the high content of Ni, since there are cases where the corrosion resistance is deteriorated, the upper limit of the content of Zn-Mg alloy plating layer 3 of Ni, it is preferable to 1.50%. The content of Ni in the Zn-Mg alloy plating layer 3 is preferably more than 0.10 mass%.
Incidentally, Ni is may be in the manner contained in the plating alloy as a pre-Ni plating as described above, may be previously included as a component in advance plating alloy.
[0031]
　The Zn-Mg alloy plating layer 3, there is a case where the elements constituting the steel sheet 2 as the base material is mixed. In particular, the elements at the interface and the case of forming a Zn-Mg alloy plating layer 3 in hot dipping, when subjected to heat treatment after Zn-Mg alloy plating layer 3 formed, a steel plate 2 and the Zn-Mg alloy plating layer 3 There mutual diffusion. In such a case, Fe, Al, by Zn or the like to form an alloy phase, to improve adhesion to the steel plate 2 and the Zn-Mg alloy plating layer 3. Incidentally, the alloy phase containing Fe, Al, and Zn is formed at the interface between the steel plate 2 and the Zn-Mg alloy plating layer 3 is less likely affect the corrosion resistance of Zn-Mg alloy plating layer 3.
　For the reasons mentioned above, even if the plating bath does not contain Fe, there is a case where the content of Fe in the Zn-Mg alloy plating layer 3 is about 2.0 wt%, Zn-Mg alloy plating little influence on the corrosion resistance of the layer 3. Thus, Zn-Mg alloy plating layer 3 may contain a 2.0 wt% or less of Fe.
[0032]
Zn-Mg alloy plated steel sheet 1, on the surface of the Zn-Mg alloy plating layer 3, Mg salts or the carbon number of the carboxylic acid carbon number of 4-20 is 4-20 alkanes having a corrosion product layer 4 containing Mg salt of a sulfonic acid.
　Mg salt of a carboxylic acid or an alkane sulfonic acid carbon number of 4-20 is a stable corrosion products, enhancing the corrosion resistance of the Zn-Mg alloy plated steel sheet 1.
[0033]
　Alkali metal salts of an alkali metal salt or an alkanesulfonic acid of the carboxylic acid contained in the chemical conversion treatment layer 5 is ionized and eluted into the aqueous solution under the chemical conversion treatment step and corrosive environments. And ions generated in this manner, by the Mg ions eluted from Zn-Mg alloy plating layer 3 are reacted, Mg salts or Mg salts of alkanesulfonic acid of the carboxylic acid contained in the corrosion product layer 4 is produced It is. To Mg salts or Mg salts of alkanesulfonic acid of the carboxylic acid is generated, an alkali metal salt or alkali metal salt of alkanoic acid carboxylic acid contained in the chemical conversion treatment layer 5 is, Zn-Mg alloy plating layer 3 It must be present in the contact position.
　Alkali metal salts or alkali metal salts of alkanesulfonic acids of the carboxylic acid is dissolved in the aqueous solution, and, in order to Mg salt of Mg salt or alkanesulfonic acid of the carboxylic acid is prevented from eluting into the aqueous solution, the carboxylic acid or it is necessary that the difference in solubility of an alkali metal salt and Mg salt of alkanesulfonic acid is large.
[0034]
　To precipitate between the Mg salt of a carboxylic acid or an alkane sulfonic acid and chemical conversion layer 5 Zn-Mg alloy plating layer 3 needs low solubility to water of Mg salt of a carboxylic acid or an alkane sulfonic acid . Therefore, the carbon number of a carboxylic acid or an alkane sulfonic acid 4 or more.
　A carboxylic acid or an alkane sulfonic acid in an aqueous solution in a corrosive environment is eluted as ions, it is necessary solubility in water of the alkali metal salt of a carboxylic acid or an alkane sulfonic acid is large. Therefore, the carbon number of a carboxylic acid or an alkane sulfonic acid and 20 or less.
　A preferable carbon number of the carboxylic acid or an alkane sulfonic acid is 5 to 20, more preferably from 8-12.
[0035]
　Carboxylic acids can be carbon atoms is not particularly limited as long as 4 to 20, saturated fatty acids, hydroxy carboxylic acids, benzene carboxylic acid, dicarboxylic acid, the like unsaturated fatty acids. From an economic standpoint, it is preferable to use a saturated fatty acid as the carboxylic acid.
　Examples of saturated fatty acids, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, pentadecyl acid, palmitic acid, stearic acid, and the like arachidic acid be able to.
　Examples of particularly preferred compounds among the saturated fatty acids, caprylic acid carbon number of 8-12, pelargonic acid, capric acid and lauric acid.
[0036]
　Examples of hydroxy carboxylic acids, malic acid, citric acid, and tartaric acid. Benzene carboxylic acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, and the like cinnamic acid.
　Examples of the dicarboxylic acid include fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.
　Examples of unsaturated fatty acids, crotonic acid, sorbic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linolenic acid, arachidonic acid, eicosadienoic acid, eicosapentaenoic acid it can be mentioned.
[0037]
　Is not particularly limited as long as it is 4 to 20 carbon also alkanesulfonic acid, butanoic acid, 2-butanoic acid, pentanoic acid, hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecane sulfonic acid, hexadecane sulfonic acid, octadecanoic acid, can be used equalize San sulfonic acid.
　Examples of particularly preferred compounds among the alkanesulfonic acid, octanoic acid carbon number of 8-12, decane sulfonic acid and dodecane sulfonic acid.
[0038]

　Zn-Mg alloy plated steel sheet 1, on the surface of the corrosion product layer 4, having a chemical conversion layer 5 made of an alkali metal salt and a film forming component of a carboxylic acid or an alkane sulfonic acid. The chemical conversion layer 5, if necessary, the inhibitor component, and the polyethylene wax may contain. Chemical conversion layer 5 is preferably a so-called chromate-free.
[0039]

　alkali metal of the alkali metal salt of a carboxylic acid or an alkane sulfonic acid contained in the chemical conversion treatment layer 5 is at least one of Li, Na, K, selected from the group consisting of Rb and Cs. From an economic standpoint, the alkali metal is only Na (alkali metal salt of a carboxylic acid or an alkane sulfonic acid is only Na salt of a carboxylic acid or an alkane sulfonic acid, does not include the alkali metal salts other than Na salt) is preferable.
[0040]
　The content of the alkali metal salt of a carboxylic acid or an alkane sulfonic acid contained in the chemical conversion treatment layer 5 is, 10 ~ 1500mg / m in Na amount 2 is preferably. The content of the alkali metal salt of a carboxylic acid or an alkane sulfonic acid is 10 mg / m in weight Na 2 for is less than the amount of Mg salt of a carboxylic acid or an alkane sulfonic acid contained in the corrosion product layer 4 is small, suitably there is a case in which such can not be obtained corrosion resistance. On the other hand, the content of the alkali metal salt of a carboxylic acid or an alkane sulfonic acid is 1500 mg / m in weight Na 2 exceeds, in some cases the uniformity of the chemical conversion layer 5 may be deteriorated.
[0041]
　The chemical conversion layer 5 and drying a solution obtained by immersing in pure water, using the obtained residue, by performing qualitative and quantitative analysis by infrared spectroscopy or pyrolysis gas chromatography, the carboxylic acid or identification of materials of an alkali metal carboxylic acid component or an alkane sulfonic acid salts of alkanesulfonic acids are possible. Using the residue obtained in the same manner as described above, it is possible to measure the identification and the content of the alkali metal component by performing qualitative and quantitative analysis by atomic absorption spectrophotometry. Among the alkali metal components, Na is capable of qualitative analysis and quantitative analysis by uranyl acetate salt method.
[0042]
　Chemical conversion layer 5 may contain Mg salt of a carboxylic acid or alkanesulfonic acid but, Mg salts of carboxylic acids or alkane sulfonic acids contained in the chemical conversion treatment layer 5 is hardly contribute to the improvement of corrosion resistance.
　Further, the carboxylic acid or an alkanesulfonic acid in the chemical conversion layer 5 is present only as an aspect of an alkali metal salt or Mg salt, a carboxylic acid or an alkane sulfonic acid is not present alone in the chemical conversion treatment layer 5. Similarly, in the chemical conversion treatment layer 5, the alkali metal is not present alone.
[0043]

　film-forming component, if so-called chromate-free, in particular any type, it is possible to use those containing one or both of resin and metal compound,
　as examples of the resin include a polyurethane resin , epoxy resins, acrylic resins and polyamide resins. Metal compounds may include such basic zirconium compound or a silicon compound. Examples of silicon compounds are organic silicon compounds, inorganic silicon compounds.
[0044]
　In the following, examples of preferred film forming ingredient, basic zirconium compound, a film forming component (film-forming component A) containing at least one organic acid of the phosphate compound and cobalt compound, the organosilicon compound and water-borne urethane film-forming component containing a resin (film-forming component B), a silanol group, an ethylene having one or both of an alkoxysilyl group - unsaturated carboxylic acid copolymer resin, film forming component containing a silicon oxide particles and the organic titanium compound ( film-forming component C) will be described.
[0045]

　film-forming component A, basic zirconium compound, and at least one organic acid of phosphoric acid compounds and cobalt compounds.
　Examples of basic zirconium compound, [Zr (CO as the cation 3 ) 2 (OH) 2 ] 2- or [Zr (CO 3 ) 2 (OH) 2 ] 2- and zirconium carbonate compound having, these cations ammonium salts containing, potassium salt, sodium salt. 　Examples of phosphoric acid compounds, phosphoric acid and its ammonium salt, for example, orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, phytic acid, phosphonic acid, ammonium phosphate, ammonium dihydrogen phosphate, phosphorous diammonium hydrogen, sodium phosphate, and potassium phosphate. 　Examples of cobalt compounds, cobalt carbonate, cobalt nitrate, etc. cobalt acetate and the like.

[0046]
　Examples of organic acids, glycolic acid, malic acid, tartaric acid, oxalic acid, citric acid, ascorbic acid, lactic acid, dehydroacetic acid, dehydroascorbic acid, gallic acid, tannic acid, etc. phytic acid. These organic acids it may be ammonium salts.
[0047]

　film-forming component B, containing an organic silicon compound and water-borne urethane resin.
　Examples of the organic silicon compound, a silane coupling agent containing one amino group in the molecule, the resulting compound of the glycidyl groups are blended and one containing silane coupling agents in the molecule.
　The silane coupling agent containing one amino group in the molecule, is not particularly limited, it can be exemplified 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane. The silane coupling agent containing one glycidyl group in the molecule, can be exemplified 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyl triethoxysilane.
[0048]
　The number of functional groups in the organosilicon compound is preferably 2 or more. If the number of functional groups is one, adhesion between the Zn-Mg alloy plating layer 3, binding to the self-crosslinking and polyether polyurethane resin of the organic silicon compound is decreased, the chemical conversion layer 5 it may not be suitably formed.
　The number of functional groups of the organic silicon compound can be analyzed by gas chromatography.
[0049]
　Aqueous urethane resin is preferably a polyether. Polyester polyurethane resins may arise hydrolyzed by acid or alkali, polycarbonate polyurethane, it tends to form a hard and brittle coating may be poor in corrosion resistance of the adhesion and processing unit during processing.
[0050]
　Structure of the water-based urethane resin, 3330Cm in infrared spectroscopy -1 (N-H stretching), 1730 cm -1 (C = O stretching), 1530 cm -1 (C-N), 1250 cm -1 of the (C-O) it can be analyzed by characteristic absorption.
[0051]

　film-forming component C is an ethylene has either or both of the silanol group and an alkoxysilyl group - containing unsaturated carboxylic acid copolymer resin, silicon oxide particles, and organic titanium compounds.
　Ethylene with one or both of the silanol group and an alkoxysilyl group - unsaturated carboxylic acid copolymer resin, for example, ethylene and an aqueous solution prepared by dispersing a copolymer resin of an unsaturated carboxylic acid, and silane compounds obtained by reacting. Examples of unsaturated carboxylic acids, for example, acrylic acid, methacrylic acid, maleic anhydride and the like.
　The silicon oxide particles, it is preferred to use colloidal silica or fumed silica.
[0052]
　Organotitanium compounds, for example, dipropoxybis (triethanolaminato) titanium, dipropoxybis (diethanol Minato) titanium, dibutoxybis (triethanolaminato) titanium, dibutoxybis (diethanol Minato) titanium, dipropoxybis (acetylacetonato ) titanium, dibutoxybis (acetylacetonato) titanium, dihydroxy bis (lactato) titanium monoammonium salt, dihydroxy bis (lactato) titanium di-ammonium salt, propane dioxy titanium bis (ethylacetoacetate), oxo titanium bis (monoammonium oxalate), etc. it can be mentioned.
[0053]
　Film-forming component C, in addition to the aforementioned components may include a polyurethane resin having either one or both of the silanol group and an alkoxysilyl group. Polyurethane resins having one or both of the silanol group and an alkoxysilyl group can be obtained by reacting a polyurethane prepolymer with alkoxysilanes and polyamine having an active hydrogen group.
[0054]
　Even when the film-forming component C contains an unsaturated carboxylic acid, as described above, and drying a solution obtained by immersing the chemical conversion layer 5 of pure water, by analyzing the obtained residue if, discrimination between the alkali metal salt of a carboxylic acid or an alkane sulfonic acid is possible.
[0055]
　Chemical conversion layer 5 is fluoride and containing at least one selected from the group consisting of trivalent chromium and vanadium, since Mg salts of carboxylic acid or alkanesulfonic acid is not properly precipitation, corrosion product layer 4 is preferably not formed. Therefore, the chemical conversion layer 5, the fluoride, it is preferred not to contain trivalent chromium and vanadium.
　Moreover, the chemical conversion treatment layer 5 fluoride, in order not contain trivalent chromium and vanadium, fluoride also film-forming component, it is preferred not to contain trivalent chromium and vanadium.
[0056]
　The interface between the Zn-Mg alloy plating layer 3 and the interface and corrosion product layer 4 of the corrosion product layer 4 and the chemical conversion treatment layer 5 is taken of a cross-section of the Zn-Mg alloy plated steel sheet 1 SEM-by reflected electron image it can be identified by the brightness of the reflected electron image.
[0057]
(Method of manufacturing a Zn-Mg alloy plated steel sheet
　1) Zn-Mg alloy plated steel sheet 1, the Zn-Mg alloy plating layer 3 is formed on the surface of the steel plate 2 by a plating process, Zn-Mg alloy plating layer by chemical conversion treatment step 3 to form a corrosion product layer 4 on the surface of the are made by forming a chemical conversion layer 5 on the surface of the corrosion product layer 4.
[0058]

　The plating process to form a Zn-Mg alloy plating layer 3 on the surface of the steel plate 2.
　The method of plating step is not particularly limited, and may be a known melt plating. For even the addition of Mg or the like to Zn plating bath may be a known method.
[0059]

　The chemical conversion treatment step, to form a Zn-Mg alloy plating layer surface corrosion product layer 4 of 3 to form a chemical conversion treatment layer 5 on the surface of the corrosion product layer 4.
　In the chemical conversion treatment step, regardless of the type of film-forming component of the chemical conversion layer 5, a solution where the alkali metal salt of a carboxylic acid or an alkane sulfonic acid and a film-forming components are dissolved in water or an organic solvent (hereinafter, the chemical conversion treatment solution designations to) and applied to the surface of the Zn-Mg alloy plating layer 3 and dried.
　The concentration of the alkali metal salt of a carboxylic acid or an alkane sulfonic acid in the chemical conversion treatment solution is not particularly limited, alkali metal salts or alkali metal salts of alkanesulfonic acids of the carboxylic acid is dissolved in the aqueous solution, and, Mg salts of carboxylic acids or Mg salts of alkanesulfonic acid from the viewpoint to avoid dissolution in the aqueous solution, preferably 0.1 to 10 mass%.
[0060]
　The method of coating chemical conversion treatment solution is not particularly limited, for example, spraying, dipping, roll coating, shower Ringer method may be employed such as an air knife method.
　Chemical conversion treatment liquid, surfactants, defoamers, may contain lubricants or fillers.
　After applying the chemical conversion treatment liquid, for drying, a Zn-Mg alloy plated steel sheet 1 chemical conversion treatment liquid has been applied may be heated to 50 ℃ ~ 200 ℃.
Example
[0061]
　The present invention will be specifically described by Examples and Comparative Examples of the present invention are shown below, but the present invention is not limited to these.
[0062]
　The steel plate thickness is 0.8 mm, using a known melt plating, coating weight of 180 g / m per sided 2 (attached amount is respectively 90 g / m per surface 2 ) a is Zn-Mg alloy plating to form a layer. Furthermore, Zn-Mg total thickness of the alloy plating layer was formed corrosion product layer and the chemical conversion layer is 1.2 [mu] m.
　Method of forming a corrosion product layer and the chemical conversion treatment layer, 1 wt% of an alkali metal salt of a carboxylic acid or an alkane sulfonic acid, Zn-Mg the chemical conversion treatment solution containing 20 wt% and water film-forming components in the bar coating It was coated on the alloy plating layer.
　The composition of the Zn-Mg alloy plating layer, an alkali metal salt of a carboxylic acid or an alkane sulfonic acid contained in the chemical conversion treatment layer, the film-forming components shown in Tables 1-5. Using these Zn-Mg alloy plated steel sheet as a test piece was evaluated blackening and the corrosion resistance as an indicator of the primary rust resistance. The evaluation results are shown in Table 6 to 10.
[0063]
　Incidentally, the invention examples described in Table 1 and 2 includes an alkali metal salt of a carboxylic acid chemical conversion treatment layer, the invention examples described in Table 3 and 4 include alkali metal salts of alkanesulfonic acid chemical conversion layer They are out. In the comparative example in Table 5, when the chemical conversion treatment layer containing an alkali metal salt of a carboxylic acid, and a case which contains neither the case and both comprise alkali metal salts of alkanesulfonic acids.
[0064]
[Blackening]
　using constant temperature and humidity tester, a 80 ° C. and a relative humidity (RH) 85% specimen under an atmosphere of allowed to stand for 144 hours. The color tone of the test piece after 144 hours electrostatic置前measured by spectrophotometer was evaluated blackening resistance. Specifically, CIE colorimetric system with spectrophotometer (L * a * b * L represents the lightness of color system) * values were measured, the 144-hour static置前L * values and 144 hours static After incubation of the L * value and the difference (i.e., (L in 144 hours electrostatic置前* value of) - (L * value of)) △ L a * was determined.
　[Delta] L * based on the value of, and rated the blackening resistance as follows. "Very Good", "Good", was passed the "Fair".
　Very Good: △ L * 5 or less
　Good: △ L * 5 Ultra 10 or less
　Fair: △ L * is 10 super 15 or less
　Bad: △ L * is greater than 15
[0065]
　Above L * represents the bright colors larger value represents the darker color (black) value is smaller. 144 h L of the static置前after specimen * is a difference value [Delta] L * has been evaluated blackening based on, [Delta] L * keep the higher standing even static置前and close the lightness value of less indicating that you are. Further, [Delta] L * after standing as the value is large indicates that the lowered lightness than static置前(be dark).
[0066]
Corrosion Resistance
　to specimens, by carrying out the salt spray test conforming to JIS Z 2371 240 hours to evaluate the corrosion resistance. Specifically, the corrosion resistance was determined by the following criteria at the corrosion area ratio after the salt spray test (ratio of the corroded area to the surface area of the test piece). "Very Good", "Good", was passed the "Fair".
　Very Good: corroded area ratio of
　0% Good: corroded area ratio of 0% and 5%
　Fair: corrosion area ratio is more than 5% to 30%
　Bad: corroded area ratio of 30 percent
[0067]
　In Tables 6-10, were comprehensive two evaluation described above, also shown together Overall evaluation. In the overall evaluation, "Very Good", "Good", was passed the "Fair".
[0068]
[Table 1]

[0069]
[Table 2]

[0070]
[table 3]

[0071]
[Table 4]

[0072]
[table 5]

[0073]
[Table 6]

[0074]
[Table 7]

[0075]
[Table 8]

[0076]
[Table 9]

[0077]
[Table 10]

[0078]
　As shown in Table 6-9, the inventive examples are excellent in both blackening resistance and corrosion resistance, the overall evaluation was passed.
[0079]
　On the other hand, Comparative Examples 1, 2, 5 and 6 shown in Table 10 are outside the scope of the present invention the Mg content of the alloy plating layer, blackening resistance, corrosion resistance and overall evaluation is insufficient. In Comparative Examples 1 and 5 are comparative examples containing a large amount of Mg alloy plating layer. In Comparative Examples 1 and 5, although the corrosion product layer was formed, blackening, corrosion resistance and overall evaluation is insufficient. This may be due, formation itself of the Comparative Examples 1 and 5, the corrosion product layer takes place, the corrosion of the Mg phase present in the plating fast, it believed it was not possible to inhibit corrosion.
　Comparative Examples 3, 4, 7 and 8 are outside the scope of the carbon atoms of the carboxylic acid or an alkane sulfonic acid present invention, blackening, corrosion resistance and overall evaluation is insufficient.
　Comparative Examples 9-12, contains no alkali metal salt of a carboxylic acid or an alkane sulfonic acid, blackening, corrosion resistance and overall evaluation is insufficient.
[0080]
　Comparative Example 13, because they did not subjected to plating on the steel sheet, blackening, corrosion resistance and overall evaluation is insufficient. In Comparative Example 13, because no plated steel plate, a source of Mg ions is absent. Therefore, not formed Mg salts of carboxylic acids, for corrosion product layer is not formed, blackening is believed that corrosion resistance and overall evaluation is insufficient.
　Comparative Examples 14 and 15, but includes a carboxylic acid or an alkane sulfonic acid, because it does not contain an alkali metal salt of a carboxylic acid or an alkane sulfonic acid, blackening, corrosion resistance and overall evaluation is insufficient.
[0081]
　Comparative Example 16 is a comparative example in which film-forming component contains a trivalent chromium, blackening, corrosion resistance and overall evaluation is insufficient.
　Comparative Example 17 is a comparative example in which film-forming component contains vanadium, blackening resistance, corrosion resistance and overall evaluation is insufficient.
　Comparative Example 18 is a comparative example in which film-forming component contains fluorine, blackening resistance, corrosion resistance and overall evaluation is insufficient.
　Film-forming component is trivalent chromium, as the undesirable reasons when vanadium or fluorine, when the film-forming component contains a trivalent chromium, vanadium or fluorine, is Mg salts of carboxylic acid or alkanesulfonic acid without properly precipitation, corrosion product layer is believed to be due to not suitably formed.
Industrial Applicability
[0082]
　According to the above embodiment, it is possible to provide a Zn-Mg alloy plated steel sheet having a superior with primary rust resistance, chemical conversion treatment layer
DESCRIPTION OF SYMBOLS
[0083]
　1 Zn-Mg alloy plated steel sheet
　2 steel
　3 Zn-Mg alloy plating layer
　4 corrosion product layer
　5 chemical conversion treatment layer

The scope of the claims
[Claim 1]
　Steel plate and;
　formed on the surface of the steel sheet, 1.0 contains ~ 70.0% by weight of Mg, Zn-Mg alloy plating layer balance containing Zn and impurities and,
　the surface of the Zn-Mg alloy plating layer it is formed on the corrosion product layer and containing either one of the Mg salt of alkanesulfonic acid Mg salt and the carbon number of the carboxylic acid carbon number of 4-20 is 4-20;
　the corrosion products formed on the surface of the layer, if the corrosion product layer comprises a Mg salt of the carboxylic acid is an alkali metal salt of the carboxylic acid, the corrosion product layer of Mg salt of the alkane sulfonic acid when it contains is a chemical conversion layer containing an alkali metal salt of the alkanoic acid;
provided with,
　the alkali metal salts or alkali metal salts of the alkanesulfonic acid of the carboxylic acid contained in the chemical conversion treatment layer Alkali metal is at least one of Li, Na, K, selected from the group consisting of Rb and Cs,
characterized in that, Zn-Mg alloy plated steel sheet.
[Claim 2]
　The Zn-Mg alloy plated layer contains 5.0 to 70.0% by weight of Mg
, characterized in that, Zn-Mg alloy plated steel sheet according to claim 1.
[Claim 3]
　The Zn-Mg alloy plated layer contains 10.0 to 70.0% by weight of Mg
, characterized in that, Zn-Mg alloy plated steel sheet according to claim 2.
[Claim 4]
　The Zn-Mg alloy plated layer contains Mg of 15.0 to 70.0 wt%
characterized in that, Zn-Mg alloy plated steel sheet according to claim 3.
[Claim 5]
　The Zn-Mg alloy plating
　layer, and 0.3 to 25.0 wt%
　Al; and 0.01 to 5.00 wt%
　Si; 1.0 ~ 5.0 mass% of
　Ca; 0. 1 to 1.5 mass% of Ni;
further comprising at least one selected from the group consisting of
and wherein the, Zn-Mg alloy plated steel sheet according to any one of claims 1-4.
[Claim 6]
　Wherein the alkali metal is Na
and wherein the, Zn-Mg alloy plated steel sheet according to any one of claims 1 to 5.
[Claim 7]
　The content of the alkali metal salt of an alkali metal salt or the alkanesulfonic acid of the carboxylic acid contained in the chemical conversion treatment layer, in terms of Na 10 ~ 1500 mg / m 2 is
characterized in that, according to claim 6 Zn-Mg alloy plated steel sheet according to.
[8.]
　The carboxylic acid or carbon atoms of the alkane sulfonic acid is 5 to 20
, characterized in that, Zn-Mg alloy plated steel sheet according to any one of claims 1 to 7.
[Claim 9]
　The carbon number of the carboxylic acid or the alkanesulfonic acid is 8-12
, characterized in that, Zn-Mg alloy plated steel sheet according to claim 8.
[Claim 10]
　The carboxylic acid is a saturated fatty acid
, characterized in that, Zn-Mg alloy plated steel sheet according to any one of claims 1-9.
[Claim 11]
　The chemical conversion treatment layer, a fluoride, trivalent not containing chromium and vanadium
, characterized in that, Zn-Mg alloy plated steel sheet according to any one of claims 1 to 10.