JP2006187679A - Rustproof coated article and coating film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly impart a high rustproof effect to a metal base material over a long period of time even if a rustproof coating film is formed using a chromium-free rustproof agent. <P>SOLUTION: The rustproof coating film, which is constituted of an inorganic composition containing a metal powder and substantially containing no chromium, is formed on the rustproof substrate layer on the surface of the metal base material treated with a rustproof substrate agent to prepare a rustproof coated article. The rustproof substrate layer may be a metal phosphate coating film such as an iron phosphate coating film. The corrosion potential of the rustproof coating film may be -1,100 to -800 mV (especially about -1,100 to -900 mV) and the inorganic compound may contain at least a plate zinc powder (e.g., the plate zinc powder and a binder component, especially the plate zinc powder, a plate aluminum powder and the binder component). The rustproof coating film may be constituted of a plurality of films and may has a structure that a plate metal powder is laminated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rust-preventing coated article on which a chromium-free rust-preventive coating containing a metal powder such as zinc dust is formed, and a method for forming the coating.

  Conventionally, metal parts such as automotive parts (bolt nuts, pipes, intake manifold pipes, muffler and other automobile undercarriage parts) and washing machine parts are required to have high salt water resistance and corrosion resistance. Has been made. In such a coating treatment, a rust preventive agent such as zinc has been used in combination with a hexavalent chromium compound such as chromic acid in order to adhere firmly to metal parts (mainly iron base materials). . For example, in the dacrotized treatment, an aqueous inorganic paint mainly composed of a hexavalent chromium compound and zinc powder is applied to a metal part, and the coating film is baked at a temperature of about 300 ° C. or higher, whereby the zinc powder is applied to the metal part. Is firmly attached to give high rust prevention.

  However, it has been pointed out that hexavalent chromium compounds cause dermatitis and ulcers when in contact with the human body, and cause inflammation and carcinogenesis in the digestive organs and lungs. Accordingly, the use of hexavalent chromium compounds tends to be limited, particularly in Europe and the United States.

  Under such a flow, a new dacrozide treatment combining a zinc powder, an aluminum powder and a silicon-based binder component without using a hexavalent chromium compound has also been proposed in the dacrotized treatment (GEOMET (GEOMET)). ) Catalog (see Non-Patent Document 1)).

  As a chromium-free paint containing zinc, for example, JP-A-6-9897 (Patent Document 1) discloses a paint containing coated zinc-containing metal flakes having a colloidal silica coating on the surface. Furthermore, as a zinc-rich water-based paint, Japanese Patent Application Laid-Open Publication No. 2004-2638 (Patent Document 2) describes that an ion-exchanged water is added to an alkali silicate solution to cause hydrolysis to lower the polymerization degree. An aqueous coating material prepared by using a zinc powder-containing slurry prepared by mixing and stirring zinc powder is disclosed.

  Also, as a plating method using zinc, for example, JP-A-7-18461 (Patent Document 3) discloses an aqueous resin, a specific silicone compound, and 10 to 1500 ppm of chromium with respect to the aqueous resin. A surface treatment method for a zinc-aluminum alloy-plated steel sheet is disclosed in which a surface treatment agent containing a hexavalent chromium salt in a proportion is applied to the surface of a zinc-aluminum alloy-plated steel sheet. In this method, the content of hexavalent chromium is reduced as much as possible in zinc-aluminum alloy plating by combining an aqueous resin such as an acrylic paint and a silicone compound.

  Corrosion resistance can also be imparted to these chromium-free rust-proof coatings. However, unlike a rust-proof coating using a hexavalent chromium compound, when manufactured in large quantities industrially, there is a large variation, and high corrosion resistance cannot be reliably imparted. For example, when parts that are consumed in large quantities such as bolts and nuts are subjected to corrosion resistance, parts having poor corrosion resistance are generated in part due to non-uniformity of the processing. Moreover, it is difficult to eliminate in advance parts having poor corrosion resistance by inspection. Therefore, it is difficult to industrially reliably manufacture parts having high corrosion resistance. Moreover, compared with the rust preventive film using a hexavalent chromium compound, the corrosion resistance over a long period of time decreases.

On the other hand, conventionally, in an electrodeposition coating containing fine powder metal and a hexavalent chromium compound, it has been proposed to improve the rust prevention property by covering the obtained film with an appropriate coating agent ( JP-A-48-30739 (Patent Document 4)). However, when such an exterior coating (top coat film) is formed of a resin component or the like, the resin component causes a liquid pool in the recess or the like and is cured. For this reason, the thickness accuracy of the coating layer is lowered. For example, when the substrate is a screw, it is difficult to tighten the screw.
JP-A-6-9897 (Claims 1 and 4) JP 2004-2638 A (Claims 1 and 5) JP-A-7-18461 (Claim 1, paragraph numbers [0012] [0021]) JP-A-48-30739 (Claim 1, page 8, upper right column, line 10 to lower left column, line 14) “GEOMET catalog, March 31, 2004, ver. 3”, Nippon Dacro Shamrock Co., Ltd.

  Therefore, the object of the present invention is to provide a high corrosion resistance to a base material such as a metal part over a long period of time even when a rust-proof coating is formed with a chromium-free rust preventive agent that does not contain a harmful hexavalent chromium compound. An object of the present invention is to provide a rust-proof coated product that can be imparted with a coating film and a method for forming the coating film.

  Another object of the present invention is to provide a rust-preventive coated product that can impart high corrosion resistance to a substrate such as a metal part even under harsh conditions such as salt water, and a method for forming a film thereof. .

  Still another object of the present invention is to provide a rust-proof coating and a method for forming a coating thereof that can reliably impart high corrosion resistance to a base material such as a metal part even if industrially mass-produced. .

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that when a metal substrate is ground-treated with a specific rust-preventing base agent, a metal substrate is formed even if a rust-free coating is formed with a chromium-free rust-preventive agent. On the other hand, it was found that high corrosion resistance can be reliably imparted over a long period of time, and the present invention was completed.

  That is, the rust-preventing coated product of the present invention is composed of an inorganic composition containing a metal powder and substantially not containing chromium in the rust-preventing base layer on the surface of the metal substrate formed with the rust-preventing base agent. A rust-proof coating is formed. The rust preventive underlayer may be a metal phosphate coating such as an iron phosphate coating. The corrosion potential of the rust preventive coating may be, for example, -1100 to -800 mV (particularly about -1100 to -900 mV). The inorganic composition may contain at least a plate-like zinc powder (for example, a plate-like zinc powder and a binder component, in particular, a plate-like zinc powder, a plate-like aluminum powder and a silicon-containing binder). The rust preventive film may be composed of a plurality of layers. The antirust coating may have a structure in which plate-like metal powders are laminated.

  In the present invention, the metal substrate was treated with a rust preventive base agent, and the formed rust preventive base layer was formed after applying a rust preventive agent containing a metal powder and substantially free of chromium. A film forming method for baking the coating film is also included. In this method, a solution containing a metal hydrogen phosphate is used as a rust preventive base material, and a rust preventive agent containing at least plate-like zinc powder is used as a rust preventive agent, and applied at a temperature of about 200 to 410 ° C. The film may be fired.

  Further, in the present invention, an inorganic composition containing a metal powder and substantially free of chromium is applied to the formed rust-preventing base layer by treating the metal substrate with a rust-preventing base agent. The method of baking and improving the corrosion resistance of the metal substrate is also included. In this method, a metal substrate was treated with a solution containing a metal hydrogen phosphate, and an inorganic composition containing a metal powder and substantially free of chromium was applied to the formed antirust base layer. Then, you may bake at 200-410 degreeC. Furthermore, in the said method, the corrosion potential of a rust preventive film may be adjusted with a calcination temperature, and the corrosion resistance of a metal base material may be improved.

  In the present invention, even if a rust-preventive coating is formed with a chromium-free rust preventive agent by treating the metal substrate with a specific rust preventive primer, over a long period of time, High adhesion and corrosion resistance can be imparted. In particular, high corrosion resistance can be obtained even under severe conditions such as salt water. Furthermore, even when industrially mass-produced, high corrosion resistance can be reliably imparted to a base material such as a metal part. In particular, in the case of mass production industrially, high corrosion resistance can be obtained even if scratches are generated or different kinds of metal powder are mixed. In other words, since no harmful hexavalent chromium compound, which has been pointed out to be dangerous to the human body, is used, the same effect as when using a conventional hexavalent chromium compound can be obtained in an environmentally safe manner. .

  The anticorrosive paint of the present invention is composed of a metal substrate, an antirust base layer formed on the surface of the metal base, and an anticorrosive film formed on the antirust base layer. .

[Anti-rust base layer]
The rust preventive foundation layer of the present invention is formed by treating a metal substrate with a rust preventive primer. The rust-preventing underlayer is only required to be composed of a resin component or an inorganic compound having heat resistance with respect to the calcination temperature of the chromium-free rust preventive agent for forming the rust-preventive coating. Although it may be, it is usually formed as an inorganic coating (or a layer composed of inorganic components).

  The inorganic coating may form a coating of a single metal (such as aluminum) or a metal oxide (such as silicon oxide or aluminum oxide) by plating or the like, but by chemically treating the metal substrate itself, It is preferable to form an underlayer, and it is particularly preferable to form the underlayer with a compound generated by a chemical reaction. Such underlayers include phosphate coatings, iron oxide (eg, iron monoxide, iron trioxide, iron sesquioxide, etc.) coatings, iron sulfate coatings, iron chloride coatings, etc. An acid salt film is preferably used. In addition, in the case of triiron tetroxide coating called black dyeing treatment, the metal substrate (iron-based substrate) is treated with a base agent such as concentrated sodium hydroxide aqueous solution, and the iron contained in the metal substrate is removed. It can be formed by oxidation.

  The phosphate coating can be formed by a conventional method called bond treatment, that is, by treating a metal substrate with a phosphate treating agent (or a base agent). The phosphating agent only needs to contain at least a metal hydrogen phosphate, and is usually an aqueous solution containing a metal hydrogen phosphate, phosphoric acid, and optionally a mineral acid (such as nitric acid) or a salt thereof. is there. When the metal substrate is treated with such a phosphate treating agent, the surface of the iron-based substrate dissolved by phosphoric acid reacts with the hydrogen phosphate metal salt, and the phosphate metal salt is formed as a film. The Examples of the phosphate formed as the coating include iron phosphate, zinc phosphate, manganese phosphate, tin phosphate, sodium phosphate, and zinc calcium phosphate. Among these, in the case of an iron-based substrate, an iron phosphate coating is particularly preferable from the viewpoints of adhesion to the substrate and heat resistance.

  Such iron phosphate treatment agents are available from Nippon Parkerizing Co., Ltd. as “Palphos 525T”, “Palphos 901”, “Palphos 1077”, “Palphos 2557”, “Palphos 3454”, “Juridine 210B”, etc. it can.

The coating weight of the phosphate coating is, for example, 0.01 to 10 g / m ² , preferably 0.05 to 5 g / m ² , more preferably 0.1 to 3 g / m ² (particularly 0.3 to 1 g / m ²⁾ . m ² ).

  The thickness of the rust preventive underlayer is, for example, about 0.1 nm to 50 μm, preferably 1 nm to 10 μm, more preferably 10 nm to 5 μm (particularly 100 nm to 1 μm), depending on the application.

[Anti-rust coating]
The rust preventive coating is composed of an inorganic composition containing a metal powder and substantially free of chromium.

  That is, in the present invention, the rust-preventing coating does not substantially contain a chromium component except for a chromium component inevitably mixed. Examples of the chromium component include hexavalent chromium compounds such as chromic acid (trichromic acid, tetrachromic acid, etc.) and chromic anhydride (chromium trioxide). Specifically, the chromium content is, for example, about 10 ppm or less (for example, 0 to 10 ppm) in the film, preferably about 5 ppm or less (for example, 0 to 5 ppm), and more preferably about 1 ppm or less (for example, 0 to 1 ppm). It is.

  Examples of the metal powder include Group 2A metals (such as magnesium), Group 4A metals (such as titanium), Group 7A metals (such as manganese), Group 8 metals (such as iron, cobalt, nickel), and Group 1B metals (such as magnesium). And a metal powder composed of a single metal or an alloy such as a group 2B metal (such as zinc), a group 3B metal (such as aluminum), and a group 4B metal (such as tin). These metal powders can be used alone or in combination of two or more. Among these metal powders, zinc powder and aluminum powder are preferable, and at least one metal powder selected from zinc powder and aluminum powder (particularly, metal powder containing at least zinc powder) is preferable from the viewpoint of rust prevention. .

  The shape of the metal powder is not particularly limited, and may be spherical, rod-like, or indefinite, but plate-like shapes such as scales, flakes, and flakes are preferred. In this invention, it is preferable to have the structure where the said plate-shaped metal powder was laminated | stacked in the antirust coating. Such a laminated anticorrosive film can suppress the intrusion of rust-forming factors from the outside by forming a structure in which several tens of layers of flaky metal are laminated in the film.

  The average particle diameter of the metal powder is, for example, about 0.01 to 30 μm, preferably about 0.1 to 20 μm, more preferably about 0.1 to 15 μm (particularly about 1 to 10 μm). When the metal powder is plate-like, the average thickness of the plate-like metal powder is, for example, 0.05 to 10 μm, preferably 0.1 to 5 μm, more preferably about 0.1 to 3 μm, and the aspect ratio (average The particle size / average thickness is, for example, about 2 to 100, preferably about 3 to 50, and more preferably about 5 to 30 (particularly 5 to 20).

  The rust preventive film may further contain a binder component. The binder component may be a resin binder, but from the viewpoint of heat resistance, a silicon-containing binder, a titanium coupling agent (for example, a titanium alkoxide such as tetraisopropyl titanate or tetrabutyl titanate or a polymer thereof), zirconium, etc. Inorganic binders such as coupling agents (eg, zirconate alkoxides), particularly silicon-containing binders are preferred.

Examples of the silicon-containing binder include metal silicate salts (sodium silicate, lithium silicate, potassium silicate, calcium silicate, aluminum silicate, magnesium silicate, etc.), aluminosilicate (magnesium aluminosilicate, zeolite, kaolin). , Bentonite, etc.), silicon oxide (silicon monoxide, colloidal silica, etc.), silane coupling agents [chlorotri C _1-2 alkoxysilane, glycidyloxyalkyl-tri C _1-2 alkoxysilane, di (glycidyl) oxyalkyl) di C _1-2 alkoxysilane, aminoalkyl - tri C _1-2 alkoxysilane, di (aminoalkyl) di C _1-2 alkoxysilane, vinyl tri C _1-2 alkoxysilane, (meth) acryloyloxy alkyl - Tri C _1-2 alkoxysilane , Di ((meth) acryloyloxy alkyl) - di C _1-2 alkoxysilane, etc.], and silicone resins. These inorganic binders can be used alone or in combination of two or more. Of these inorganic binders, metal silicates, particularly alkali metal silicates (alkali silicates) such as sodium silicate, lithium silicate, and lithium silicate are preferable from the viewpoint of adhesion and heat resistance. Such an aqueous solution of an alkali metal silicate salt is called water glass and is excellent in adhesiveness, and is therefore suitable as a metal powder binder when used as a water-based paint.

  In particular, the silicon-containing binder fills the layers in a laminated structure composed of a sheet metal powder (particularly a sheet metal powder composed of zinc powder or aluminum powder) and joins adjacent layers, resulting in high rust prevention. An effect is obtained. Furthermore, by combining the rust preventive film having such a rust preventive laminate structure and the above-mentioned rust preventive base agent (particularly resin components and iron-containing compounds), the adhesion of the rust preventive film can be achieved without using a chromium compound. It significantly improves the durability and durability, and exhibits a rust prevention effect for long-term use under severe conditions.

  The proportion of the inorganic binder is, for example, 0.1 to 100 parts by weight, preferably 1 to 70 parts by weight, more preferably 3 to 50 parts by weight (particularly 5 to 30 parts by weight) with respect to 100 parts by weight of the metal powder. Degree.

  The antirust coating may be cured by coating a chromium-free antirust agent in the form of a paint. When used in the form of a paint, it usually contains a solvent and a surfactant. As a solvent, the solvent illustrated by the term of the said antirust base agent can be used. In the case of a water-based paint, it is preferable that a surfactant is further contained.

As the surfactant, for example, conventional anions, nonions, and cationic surfactants can be used. In particular, tetraalkylammonium salts (for example, mono- or di-C ₈ such as lauryltrimethylammonium chloride, dioctadecyldimethylammonium chloride). _-24 alkyl-tri or dimethylammonium salts), trialkylbenzylammonium salts [for example, C _8-24 alkylbenzyldimethylammonium salts (eg benzalkonium chloride salts) such as cetylbenzyldimethylammonium chloride], benzethonium chloride, alkylpyridinium salts (e.g., C _8-24 alkyl pyridinium salts such as cetylpyridinium bromide), cationic surfactants such as alkylamine acetates (e.g., such as octadecylamine acetate) Sexual agents, polyoxyethylene alkyl ethers (e.g., polyoxyethylene octyl ether, polyoxyethylene C _6-24 alkyl ether such as polyoxyethylene lauryl ether), polyoxyethylene alkyl phenyl ethers (e.g., polyoxyethylene octylphenyl Ether, polyoxyethylene C _6-18 alkylphenyl ether such as polyoxyethylene nonylphenyl ether), polyoxyethylene fatty acid amide (for example, polyoxyethylene C _8-24 fatty acid amide such as polyoxyethylene stearic acid amide) , Polyoxyethylene polyhydric alcohol fatty acid esters (for example, polyoxyethylene glyceryl stearate, polyoxyethylene glycerin oleate, etc. Ji like Ren glycerin C _8-24 fatty acid esters), such as nonionic surfactants such as polyoxyethylene castor oil and polyoxyethylene hardened castor oil can be preferably used. These surfactants can be used alone or in combination of two or more.

  The ratio of the surfactant is, for example, 0.01 to 30 parts by weight, preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight (particularly 1 to 100 parts by weight) with respect to 100 parts by weight of the metal powder. 5 parts by weight).

  Furthermore, the density | concentration of the metal powder in a coating material is 30-400 g / liter, for example, Preferably it is about 50-350 g / liter.

  In the present invention, the corrosion potential of the rust preventive coating is, for example, -1100 to -800 mV (for example, -1100 to -900 mV), preferably -1100 to -950 mV (for example, -1100 to -1000 mV), and more preferably-. It is about 1,080 to -980 mV (particularly -1070 to -1000 mV). When the corrosion potential of the rust preventive coating is in this range, the stability and corrosion resistance of the coating are improved. Such a corrosion potential can be controlled by the kind and thickness of the rust preventive underlayer and the firing temperature of the rust preventive coating. For example, when the above-mentioned iron phosphate coating is formed as a rust-preventing underlayer, by setting the firing temperature of the rust-preventing coating to a higher temperature (for example, about 380 ° C.), the corrosion potential within such a range. A rust-proof coating having

  The anticorrosive film may be composed of a plurality of layers (for example, two layers) from the viewpoint of improving the corrosion resistance. In the rust preventive coating composed of a plurality of layers, from the viewpoint of adhesion, each layer is preferably composed of at least a layer composed of components of the same system (particularly a layer composed of the same components). Furthermore, among the plurality of layers, each layer may be composed of layers having the same or different corrosion potentials, and at least one layer (particularly the outermost layer) is preferably composed of layers having a corrosion potential in the above range. . For example, when the anticorrosive film is composed of two layers, the same component having different corrosion potentials can be obtained by changing the firing temperature using an anticorrosive agent containing plate-like zinc dust, plate-like aluminum dust and a silicon-containing binder. You may form the two layer comprised by these. In the present invention, in particular, when the rust-proof coating is composed of a plurality of layers and the corrosion potential of the surface layer is adjusted to the above range, the generation of scratches and the dissimilar metal powders are not limited to the chromium-free rust-proof coating. It is possible to form a coating film having high corrosion resistance with little influence on mixing.

  The thickness of the anticorrosive film (the total thickness in the case of having a plurality of layers) is, for example, 1 to 100 μm, preferably 2 to 50 μm, and more preferably about 3 to 20 μm. In addition, when a rust preventive film is formed with a several layer, the thickness of each layer is the thickness of the same grade normally.

  The rust preventive film may further contain a conventional additive similar to the rust preventive base agent.

  Such chrome-free rust preventives are available as water-based rust preventives from Nippon Dacro Shamrock Co., Ltd. as “Giomet” (Chrome-Free Dacrotized) and Enomoto Chain Co., Ltd. as “Prograte”. As a solvent-type rust inhibitor, it can be obtained as “Dolflake” from Aisin Chemical Co., Ltd.

[Metal base material]
The type of the metal substrate is not particularly limited, and may be aluminum, zinc, copper, titanium, nickel, tin, magnesium, iron, or an alloy containing these metal components (for example, stainless steel). Corrosive metal substrates, particularly iron-based substrates are used. As a preferable iron-based substrate, a steel material having corrosivity is used, and the components and composition ratio of the steel material are not particularly limited.

  Examples of iron-based substrates include linear or rod-like shapes (steel bars, steel wires, etc.), plate-like substrates (eg, steel plates, steel strips, etc.), cylindrical shapes (pipes, rods, etc.), and solid shapes (castings, etc.) ) Can be used. Specifically, small iron-based substrates (bolts, nuts, cylinder tubes, brick nails, expansion joints, specially-equipped metal fittings, turnbuckle pipes, anti-frost fans, power transmission fittings, etc.) and relatively large iron-based materials Base materials (for example, railings, main pillars, guard fences for bridges, road signs, road guard fences, river fences, rockfall prevention nets, etc.) can be used. Of these, steel products that require salt resistance, non-hydrogen brittleness, and the like are particularly suitable.

  In addition, the metal base material is subjected to a conventional pretreatment, for example, a surface treatment such as a degreasing treatment or an acid cleaning treatment, or a surface processing treatment such as shot blasting, before the surface treatment with a rust preventive base agent as necessary. May be.

[Film formation method]
The rust-prevention coated product of the present invention is a rust-preventive agent (chromium-free anti-corrosion agent) which is obtained by treating a metal substrate with a rust-preventive base agent, and containing the metal powder in the formed rust-preventive base layer and containing substantially no chromium. After the rusting agent is applied, the formed coating film is baked to obtain a coating film.

  As a method for treating a metal substrate with a rust preventive base agent, when the rust preventive base agent is a baking type primer, the rust preventive base agent can be applied to the metal substrate by a conventional coating or coating method. The anticorrosive base agent applied to the metal substrate may be cured or crosslinked by heating at a temperature of 200 ° C. or higher (eg, 200 to 400 ° C.), preferably about 220 to 380 ° C. to form a film. Good.

  On the other hand, when the rust-preventing underlayer is a layer composed of an inorganic coating, the rust-preventing undercoat can be applied to the metal substrate by, for example, spraying or dipping.

  In the bondage treatment for forming the phosphate coating, the surface of the metal substrate is usually washed (degreasing treatment, etc.), and then the metal substrate (iron-based substrate) is treated with a phosphate treatment agent. Can be formed. After the treatment with the base agent, it is washed with water and may be heated at about 30 to 80 ° C. (preferably 40 to 60 ° C.) as necessary.

  In the black dyeing treatment for forming the iron tetroxide film, for example, a rust preventive base material (100 to 180 ° C., preferably 110 to 170 ° C., more preferably 120 to 160 ° C.) is used. The metal substrate may be immersed in a concentrated aqueous sodium hydroxide solution.

  As a method of applying the chromium-free rust preventive agent to the rust preventive underlayer, the chromium-free rust preventive agent is applied on the rust preventive underlayer by a conventional method (for example, dipping, roll coating, curtain coating, spray coating, etc.). It can be obtained by firing after application. As a method of applying chromium-free rust preventive agent, generally, the base metal treated substrate is dipped into chrome-free rust preventive agent in the form of water-based paint, and excess chromium-free rust preventive agent is centrifuged In many cases, a chrome-free rust inhibitor is applied by draining the solution.

  The firing temperature after applying the chromium-free rust inhibitor may be 200 ° C. or higher (for example, about 200 to 410 ° C.), for example, 280 to 420 ° C. (for example, 300 to 420 ° C.), preferably 320 It is about -410 degreeC, More preferably, it is about 350-400 degreeC (especially 360-400 degreeC) grade. In particular, when a plurality of layers are formed, it is preferable to set the firing temperature of at least one layer (particularly the outermost layer) to a high temperature range (for example, about 350 to 420 ° C., particularly about 360 to 400 ° C.). By baking the chromium-free rust preventive at such a temperature, a coated product having excellent coating film adhesion and corrosion resistance can be obtained. The baking time is usually 5 minutes to 1 hour, preferably 10 to 50 minutes, particularly about 15 to 45 minutes. By this baking, a film (rust preventive film) excellent in hydrogen embrittlement resistance, corrosion resistance (particularly salt water resistance), and heat and rust resistance can be formed.

  In the present invention, by forming a rust-preventing underlayer (particularly a metal phosphate film such as an iron phosphate coating) on a metal substrate, the range of firing temperatures at which an excellent rust-proof coating can be formed is expanded. can do. In particular, even when a chromium-free rust inhibitor is baked at the above-described high-temperature firing temperature, a rust-proof coating having high corrosion resistance can be formed.

  If necessary, a top coat layer may be formed with the above-mentioned rust preventive agent (for example, coating agent) if necessary, and it is provided with functions such as an electrical insulating or conductive film and antibacterial property. However, depending on the type of paint, care must be taken so that no liquid pool is formed.

  These steps can usually be carried out continuously, and the baking treatment can be carried out while the coated metal substrate is running in a heating furnace or a baking furnace.

  The anticorrosive coating product of the present invention has various applications that require corrosion resistance, such as automobile parts [springs such as bolts, nuts, washers, winding springs, pipes (intake manifold pipes, etc.), mufflers, brackets, connectors. , Electrical parts, etc.], household electrical appliance parts (parts such as washing machines and coolers), civil engineering and construction parts (high tension bolts, auto nails, fasteners, electrical parts, etc.), outboard motor engine parts, transport related It is useful as a base material, equipment and parts that require rust prevention against salt damage. In particular, it is useful as a coating for salt damage countermeasures (for example, undercarriage parts of automobiles) by an antifreezing agent (calcium chloride, etc.) sprayed in winter.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, about the coated goods obtained by the Example and the comparative example, the adhesiveness of the coating film and it evaluated as follows.

[Coating adhesion]
A cellophane tape (manufactured by Nichiban Co., Ltd., cellotape (registered trademark) No. 405) is applied to the coating film, and the edges of the cellophane tape are fixed instantly after eliminating bubbles by rubbing with a finger. Torn off. When peeling off, the angle between the end of the cellophane tape and the coating surface was set to 45 °. And the adhesiveness was evaluated according to the following criteria.

○: There is no peeling of the coating film. Δ: About half of the coating film area peels. ×: The coating film peels over the entire surface.

[Rust prevention]
About the bolt (number of specimens n = 5) by which the antirust coating process was carried out, the salt spray test (JIS Z2371) was done on condition of the following. And the following reference | standard evaluated by visual observation about generation | occurrence | production of red rust in the head part and leg part of a bolt. In addition, the evaluation result showed the number of samples of the applicable volt | bolt (the number of samples in 5 samples) about each evaluation of AE. Further, Comparative Examples 3 to 4 and Examples 3 to 19 were evaluated by forming an X “X” -shaped scratch (cross cut) on the head side wall of the bolt in order to clarify the difference in effect. .

(Salt spray test conditions)
Sodium chloride concentration: 50 g / L
Spray chamber temperature: 35 ± 2 ° C
Spray amount: 1 ml / 80 cm ² / hour (Evaluation criteria)
A: No red rust is generated. B: Small dot-like red rust is generated in one or several places. C: Red rust is generated. D: Remarkable red rust is generated. E: Red rust is generated over the entire surface.

[Corrosion potential]
With respect to the obtained final coated product, the corrosion potential after being immersed in a 5 wt% aqueous sodium chloride solution for 24 hours was measured using a 3.3 mol / liter silver-silver chloride electrode as a reference electrode.

Example 1
Dipping a flange bolt for automobiles (30mm under the neck, 10mm thread diameter, 1mm pitch) shot blasted after alkaline degreasing treatment and phosphating solution (trade name "Palphos 2577" manufactured by Nihon Parkerizing Co., Ltd.) It processed and formed the antirust base layer (coat weight 0.5g / m < ² >) comprised with the iron phosphate. Furthermore, this bolt was dipped in a water-based inorganic paint (trade name “Geomet 720”, manufactured by Nippon Dacro Shamrock Co., Ltd.) at room temperature (temperature 19 ° C.), and then drained using a centrifuge. After preheating at 150 ° C. for 15 minutes, baking was performed at 350 ° C. for 45 minutes to form a 4 μm-thick rust preventive coating (first coating). Further, the same treatment was repeated using a water-based inorganic paint on the bolt to form a rust preventive coating (second coating) having a thickness of 4 μm. The coating weight of the obtained antirust coating was 270 mg / dm ² . Table 1 shows the evaluation results of the obtained coated products.

Example 2
A rust preventive film was formed in the same manner as in Example 1 except that the weight of the rust preventive film was changed to 300 mg / dm ² . The evaluation results are shown in Table 1.

Comparative Example 1
A rust preventive film was formed in the same manner as in Example 1 except that the rust preventive underlayer was not formed. The evaluation results are shown in Table 1.

Comparative Example 2
A rust preventive film was formed in the same manner as in Example 2 except that the rust preventive underlayer was not formed. The evaluation results are shown in Table 1.

  In addition, about Examples 1-2 and Comparative Examples 1-2, the processing time of the salt spray test in rust prevention evaluation is 2400 hours.

  As is apparent from the results in Table 1, red rust is not generated even after the treatment for 2400 hours in the painted product of the example, but red rust is observed in some bolts in the coated product of the comparative example.

Comparative Example 3
Automotive flange bolt (30mm under neck, 6mm thread diameter, 1mm pitch) shot blasted after alkali degreasing treatment, water-based inorganic paint (made by Nippon Dacro Shamrock Co., Ltd., trade name " After immersing in Geomet 720 ") and pulling it up, it is drained using a centrifuge, preheated at 150 ° C. for 15 minutes, and baked at 350 ° C. for 45 minutes to give a rust-proof coating having a thickness of 3 μm (first coating) ) Was formed. Further, the same treatment was repeated using a water-based inorganic paint on the bolt to form a rust preventive coating (second coating) having a thickness of 3 μm. The coating weight of the obtained antirust coating was 240 mg / dm ² . Table 2 shows the evaluation results of the obtained coated products.

Comparative Example 4
A rust-preventing film was formed in the same manner as in Comparative Example 1 except that the baking temperature was 380 ° C. The evaluation results are shown in Table 2.

  In addition, about Comparative Examples 3-4, the processing time of the salt spray test in evaluation of rust prevention property is 720 hours.

  As is clear from the results in Table 2, in the coated products of Comparative Examples 3 to 4, when the baking temperature increases, the occurrence of red rust tends to increase.

Example 3
Dipping a flange bolt for automobiles (30mm under the neck, 6mm thread diameter, 1mm pitch) shot blasted after alkali degreasing, and phosphate treatment solution (trade name "Palphos 2557" manufactured by Nihon Parkerizing Co., Ltd.) It processed and formed the antirust base layer (coat weight 0.5g / m < ² >) comprised with the iron phosphate. Furthermore, after this bolt was immersed in a water-based inorganic paint (trade name “Giomet 720”, manufactured by Nippon Dacro Shamrock Co., Ltd.) at room temperature (temperature 19 ° C.), the bolt was drained using a centrifuge, After preheating at 150 ° C. for 15 minutes, baking was performed at 380 ° C. for 45 minutes to form a rust preventive coating (first coating) having a thickness of 3 μm. Further, the same treatment was repeated using a water-based inorganic paint on the bolt to form a rust preventive coating (second coating) having a thickness of 3 μm. The coating weight of the obtained antirust coating was 230 mg / dm ² . Table 3 shows the evaluation results of the obtained coated products.

Examples 4-18
A rust preventive film was formed in the same manner as in Example 3 except that the baking temperature (firing temperature) was changed to the temperature shown in Table 3. The evaluation results are shown in Table 3.

  In addition, about Examples 4-18, the processing time of the salt spray test in evaluation of rust prevention property is 720 hours.

  As is apparent from the results in Table 3, all of the coated products of Examples 3 to 18 exhibit excellent characteristics. In particular, the coated materials of Examples 3, 4, 7, 11 and 15 having a specific corrosion potential by baking the second coating film at a higher temperature have extremely high rust prevention properties.

Claims (14)

  A rust-preventing coating composed of an inorganic composition containing a metal powder and substantially free of chromium is formed on a rust-preventing base layer on the surface of a metal substrate formed with a rust-preventing base agent. Painted material.   The coated article according to claim 1, wherein the rust preventive underlayer is a metal phosphate film.   The coated article according to claim 1, wherein the corrosion potential of the anticorrosive coating is -1100 to -800 mV.   The coated product according to claim 1, wherein the inorganic composition contains at least a plate-like zinc powder.   The coated product according to claim 1, wherein the inorganic composition contains a plate-like zinc powder and a binder component.   The coated product according to claim 1, wherein the inorganic composition contains plate-like zinc powder, plate-like aluminum powder, and a silicon-containing binder.   The coated product according to claim 1, wherein the antirust coating has a structure in which plate-like metal powders are laminated.   The coated article according to claim 1, wherein the rust preventive film is composed of a plurality of layers.   The rust preventive underlayer is an iron phosphate coating, and the rust preventive coating is composed of an inorganic composition containing a plate-like zinc powder, a plate-like aluminum powder, and a silicon-containing binder, and the corrosion potential of the rust-preventive coating is − The coated article according to claim 1, which is 1100 to −900 mV.   After the metal substrate is treated with a rust preventive base agent and a rust preventive agent containing a metal powder and substantially free of chromium is applied on the formed rust preventive base layer, the formed coating film is applied. A film forming method for firing.   Use of a solution containing a metal hydrogen phosphate as a rust preventive base material, and a rust preventive agent containing at least a plate-like zinc powder as a rust preventive agent, and firing the coating film at a temperature of 200 to 410 ° C. Item 11. The method according to Item 10.   The metal substrate is treated with a rust preventive base agent, and the formed rust preventive base layer is baked by applying an inorganic composition containing a metal powder and substantially free of chromium. A method to improve corrosion resistance.   After treating the metal substrate with a solution containing a metal hydrogen phosphate and applying an inorganic composition containing a metal powder and substantially free of chromium to the formed antirust base layer, 200 to The method according to claim 12, wherein the baking is performed at 410 ° C.   The method according to claim 12, wherein the corrosion potential of the metal substrate is improved by adjusting the corrosion potential of the rust preventive coating according to the firing temperature.