JP2005054074A - Anticorrosive zinc-containing coating composition for stainless steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zinc-containing coating material for automobile parts made of stainless steel, high in corrosion preventing performance. <P>SOLUTION: The anticorrosive zinc-containing coating material for stainless steel is a one-component hardenable coating composition which contains an epoxy resin and a zinc powder, with the amount of the zinc powder smaller than those ordinarily contained in zinc-rich paints. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a zinc-containing one-component curable coating composition with improved corrosion protection for members using stainless steel.

  Conventionally, lead / tin-plated steel sheets have been used as materials for automobile parts, such as fuel tanks. However, with the emergence of environmental regulations such as lead, alternatives have been developed. Currently, stainless steel is a material that is attracting attention as an alternative. Stainless steel is originally a material with low corrosion and is used in various applications. However, since it is actually quite expensive, it has not been used much in such automotive parts. However, in order to cope with the above environmental problems, it has become necessary to use inexpensive or economical stainless steel.

  The same is true when steel steel is used, but even when stainless steel is used for the above automotive parts, there is a gap in the welded part and the fastening part that occurs during installation, and there is water and air there. Intrusions and these are retained, creating a severe corrosive environment. That is, even stainless steel having high anticorrosion properties may cause corrosion from the welded part or the gap part. Therefore, a method of preventing corrosion by sacrificial anticorrosion with zinc by applying a so-called zinc rich paint, which is generally used for anticorrosion of the above-mentioned welded portion and exhibits high anticorrosion performance, can be considered.

  However, unlike steel steel, stainless steel requires an anticorrosive paint unique to stainless steel, and it has been found that when a so-called conventional zinc rich paint is applied, the part peels off due to an action such as chipping.

  Generally, in the pre-coat world, aluminum, stainless steel, etc. are used as bases as sashes or inset walls. Since a suitable epoxy pliers are applied on these materials, and a fluorine-based paint is applied thereon as a top coat, the paint itself becomes very expensive. In addition, the baking conditions of 200 ° C. to 250 ° C. × 60 to 90 seconds are necessary, and the manufacturing cost increases. Therefore, conventionally, it has not been considered to apply both zinc rich paint and general epoxy paint to stainless steel.

  An object of the present invention is to provide a zinc-containing coating composition suitable for corrosion protection of stainless steel, not steel steel.

  The present invention provides a zinc-containing one-part curable coating composition for anticorrosion of stainless steel, comprising an epoxy resin and zinc powder, the zinc powder being contained in an amount less than that normally contained in zinc rich paint. The amount of zinc powder can be 35-50% by weight of the solids content of the paint, preferably 40-47% by weight.

  The stainless steel member to which the paint of the present invention is applied may be an automobile fuel tank, fuel pipe, or muffler.

  When the zinc-containing coating composition for anticorrosion of stainless steel of the present invention is used, a sufficient anticorrosion effect can be exhibited even if there are welded parts or gap parts in parts using stainless steel. In addition, defects such as peeling of a coating film that occurs when a conventional zinc rich paint is applied to stainless steel do not occur.

  The epoxy resin used in the present invention is suitably an epoxy resin having two or more epoxy groups in one molecule, a weight average molecular weight of about 15,000 to 50,000, and a hydroxyl value of about 100 to 500. The glass transition temperature (Tg) of the epoxy resin is 60 to 120 ° C.

  As an example of this epoxy resin, the epoxy resin obtained by making it react with excess epichlorohydrin or alkylene oxides, such as a polyhydric alcohol and a polyhydric phenol, can be mentioned. Examples of the polyhydric alcohol include ethylene glycol, polyethylene glycol, propylene glycol, neopentyl glycol, butylene glycol, hexanediol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, diglycerol, sorbitol, and the like. For example, 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], halogenated bisphenol A, 4,4-dihydroxyphenylmethane [bisphenol F], tris (4-hydroxyphenyl) propane, resorcin, tetra Examples thereof include hydroxyphenyl ethane, novolac type polyhydric phenol, cresol type polyhydric phenol and the like. Examples of other epoxy resins include 1,2,3-tris (2,3-epoxypropoxy) propane, phthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, dimer acid Examples include diglycidyl ester, tetraglycidylaminodiphenylmethane, 3,4-epoxy-6-methylcyclohexylmethyl carboxylate, triglycidyl isocyanurate, 3,4-epoxycyclohexylmethyl carboxylate, and polypropylene glycol glycidyl ether.

  Conventional epoxy resin coatings generally form a coating film by crosslinking reaction using a curing agent. On the other hand, the modified epoxy resin of this time can be used as a lacquer because it has been made high molecular weight in advance. That is, it can be used as a one-component curable coating. Therefore, the adhesiveness, anticorrosiveness, and workability which were excellent without the complexity of the operation | work which mixes a hardening | curing agent immediately before high temperature baking or a two-component mixing type are obtained. However, the drying conditions vary, and good performance is obtained from room temperature to about 180 ° C. × 20 minutes.

  The zinc powder used in the present invention has an average particle diameter of 2 to 20 μm, preferably 5 to 10 μm, and is a metal zinc powder or a metal zinc alloy powder used in ordinary zinc rich paint, particularly metal zinc powder. Is preferred. Furthermore, it is desired to use zinc powder that has been treated to prevent sedimentation or the like. If the average particle size is less than 2 μm, sufficient adhesion after corrosion resistance cannot be obtained. On the other hand, if it exceeds 20 μm, the anticorrosion property is lowered, which is not preferable.

  The content ratio of the zinc powder is 35 to 50% by weight, preferably 40 to 47% by weight, based on the solid content of the paint, and if the content ratio is less than 35% by weight, sufficient sacrificial corrosion resistance cannot be obtained. If it exceeds wt%, the adhesion is poor, chipping resistance is poor, and peeling occurs. Moreover, you may use together other metal powders, such as aluminum powder and copper powder, for example with the said zinc powder.

  In the present invention, normal extender pigments, rust preventive pigments and colored pigments can be blended as necessary in addition to the above as necessary, such as talc, mica, barium sulfate, titanium oxide, silica, alumina, iron phosphide, MIO, lead cyanamide, zinc chromate, zinc phosphate, calcium phosphate, barium metaborate, zinc molybdate, aluminum molybdate, bengara, cyanine color pigment, carbon black and the like.

  If necessary, the composition of the present invention may further contain paint additives such as organic solvents, modified resins, sagging inhibitors, dispersants, and plasticizers.

  The base material on which the paint of the present invention is applied is preferably a part assembled by processing a plurality of parts using stainless steel, but can also be applied to other parts. In particular, a fuel pipe, a fuel tank, a muffler and the like made of stainless steel are more preferable.

  The paint is applied to the stainless steel substrate after mixing the above components. The application method is not particularly limited, and examples thereof include dip coating, flow coating, and air spray coating. The film thickness is 20-60 microns, preferably 20-40 microns. The substrate is subjected to a surface treatment if necessary. Surface treatment is basically performed in an acidic bath.

  The invention is explained in more detail by means of examples. Examples Central and% are based on weight.

Examples 1 and 2 and Comparative Examples 1 to 3
By adding zinc powder to the coating composition below, zinc-containing coatings with various amounts of zinc powder were prepared.
Ingredient Weight part (a) Epoxy resin 16
(Bisphenol A type epoxy resin, manufactured by Arakawa Chemical Industries, Ltd., hydroxyl value 225, Mw = 20,000)
(B) extender pigment 30.2
(Precipitated barium sulfate (manufactured by Sakai Chemical Co., Ltd.) and talc (manufactured by Takehara Chemical Co., Ltd.))
(C) Rust prevention pigment 5
(LF Bowseed (manufactured by Kikuchi Color Co., Ltd.)
(D) Color pigment 1.5
(Mitsubishi Carbon Black MA-100) (Mitsubishi Chemical Corporation)
(E) Additive 2.2
(Disparon 4200-20) (Enomoto Kasei Co., Ltd.)
(F) Solvent 45.1
(Xylene / cyclohexanone = 1/1)
Total 100

  The zinc powder in the obtained paint was 28 wt%, 44 wt%, 54 wt% and 60 wt% of the solid content of the paint. These paints were applied to R-410DH stainless steel plate and R-436LT stainless steel plate commercially available from Kawasaki Steel Co., Ltd. at a thickness of 20 μm, and the performance (heat resistance adhesion and corrosion resistance) of the coating film was examined. The results are shown in Table 1.

Heat-resistant adhesion After coating the sample on the sample as described above, it was kept in an environment of a temperature of 20 ° C. and a relative humidity of 70% for one week. Subsequently, it hold | maintained at 400 degreeC for 1 hour, and another coating plate was hold | maintained for 10 hours, and adhesiveness was investigated about both coating plates. The results are shown in Table 1. The adhesiveness was cut in a gob-like shape with a width of 1 mm on the coating, peeled off after the adhesive tape was attached, and it was confirmed how many gob-eyes remained. The results were evaluated as follows.
○ 90/100 or more △ 89-50 / 100
× 50/100 or less

  Table 1 also lists the products of Nippon Paint Co., Ltd., which are commercially available for use as a comparative example. Nippinzinki has a zinc content of 72% by weight.

Corrosion resistance The sample is coated to a thickness of 20 μm and cured for one week (20 ° C. × 70% indoor standing), followed by a Grappero test. As for the contents, 100 g of 7-12 mm basalt is sprayed at an angle of 90 ° C. from a distance of 35 mm.

  The panel is tested in a combined cycle corrosion test. The conditions were 5% saline spraying at 35 ° C. for 30 minutes, and then drying at 60 ° C. and relative temperature (RH) ≦ 40% for 1 hour. Then, it was treated for 1 hour under wet conditions (40 ° C., RH ≧ 95%). This is a result of performing 90 cycles with the entire process (2.5 hours) as one cycle.

Evaluation was as follows.
○ ・ ・ ・ Blister is less △ ・ ・ ・ Blister is normal × ・ ・ ・ Blister is more

Claims (4)

A zinc-containing one-component curable coating composition for anticorrosion of stainless steel, comprising an epoxy resin and zinc powder, the zinc powder being contained in an amount less than that normally contained in zinc rich paint. The zinc-containing one-component curable coating composition for anticorrosion of stainless steel according to claim 1, wherein the zinc powder is present in an amount of 35 to 50% by weight of the solid content of the coating. The zinc-containing one-component curable coating composition for anticorrosion of stainless steel according to claim 1, wherein the zinc powder is present in an amount of 40 to 47% by weight of the solid content of the coating. The zinc-containing one-component curable coating composition for anticorrosion of stainless steel according to claim 1, wherein the epoxy resin has a weight average molecular weight of 15,000 to 50,000, a hydroxyl value of 100 to 500, and a glass transition temperature of 60 to 120 ° C.