JPH0718026B2 - Surface treatment method for stainless steel - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for surface treatment of stainless steel. More specifically, it relates to a treatment method for the purpose of preventing oxidation and rust prevention of the surface of stainless steel by applying a specific substance to the surface of stainless steel and heat-treating it.

According to the present invention, since a transparent coating having high rust resistance, heat resistance, water resistance and high hardness is applied to the surface of stainless steel, the stainless steel material is used for building materials such as bathtubs and sinks, and electric stoves. It is extremely useful as a material for electrical equipment such as reflectors, chemical industrial machinery such as cleaning equipment, medical equipment and the like.

[0003]

2. Description of the Related Art Conventionally, stainless steel has been widely used in various fields as an iron which does not rust as its name suggests. In fact, iron is easily oxidized in the presence of water and oxygen to form various types of iron oxide, and the volume thereof is apt to increase, so-called rust is easily generated, whereas stainless steel is hard to be oxidized and rust in a normal environment.

Usually, a special steel mainly composed of chromium steel containing about 12% or more of Cr and added with Ni, Mo, Ti, Nb, etc. is generically called stainless steel. In this stainless steel, 13% of Cr is contained. Standard composition martensite type, Cr 18% standard composition ferrite type, Cr1
8% -Ni8% is austenite type with standard composition,
Corrosion resistance is best in the austenite type, followed by ferrite type and martensite type.

[0005]

However, depending on the type of stainless steel, the color of the surface may change due to strong heat such as welding, or rust may occur due to long-term use. It is thought to be caused by surface oxidation.

[0006] As a method for preventing the oxidation of the surface of the stainless steel, a method of applying a suitable rust preventive oil is generally used, but since it is only temporary rust preventive, it is a permanent rust preventive method. Is currently required.

An object of the present invention is to provide a surface treatment method for semi-permanently preventing the surface of stainless steel from being oxidized or rusted.

[0008]

The method of surface treatment of stainless steel according to the present invention comprises applying a silane compound hydrolyzed and polycondensed with phosphoric acid as a catalyst to the surface of stainless steel, and then subjecting it to heat treatment. .

Here, by using phosphoric acid for the hydrolysis / polycondensation of the silane compound, the hydrolysis / polycondensation reaction of the silane compound proceeds at room temperature as a catalyst to form a reaction product having high transparency. At the same time as it is obtained, phosphoric acid itself is incorporated into the hydrolysis / polycondensation reaction product of silane, which also has the effect of binding to iron on the surface of stainless steel, as shown in the chemical formula below, and thus adheres to the coating film. Play a role in improving sex. Therefore, the use of phosphoric acid as a constituent of the present invention is essential.

[0010]

As the phosphoric acid, pure 85% phosphoric acid for chemicals is preferable, but 75%, 89%, 100% phosphoric acid or 105%, 115-116% polyphosphoric acid can also be used. The ratio of phosphoric acid to silane compound is 1 to 20 parts of phosphoric acid, preferably 5 parts to 100 parts of silane compound.
~ 15 parts.

The silane compound is preferably methyltrimethoxysilane. The hydrolysis / polycondensation reaction product of methyltrimethoxysilane forms a hard and heat-resistant film.

In the present invention, a colorant such as a pigment, an inorganic filler, a defoaming agent, a thixotropy-imparting agent, etc. may be added to the silane hydrolysis / polycondensation reaction product, if necessary.

The surface treatment method of stainless steel of the present invention comprises dipping the silane hydrolysis / polycondensation reaction product into
It is carried out by applying to the surface of stainless steel by an appropriate means such as spraying or brushing, drying (touch drying), and heat-treating at least at 300 ° C. or higher.

The temperature of 300 ° C. or higher is necessary for the phosphoric acid component incorporated in the silane hydrolysis / polycondensation reaction product to react with the base material to form an insoluble film which is not dissolved and removed even by boiling water. It is the value confirmed by experiments that it is the lower limit temperature.

The heat treatment at 300 ° C. or higher may be carried out after the silane hydrolysis / polycondensation reaction product is applied to the surface of stainless steel and dried, or as a material such as heating by welding or a stove reflector. When used, a method of actually igniting and heating the stove may be used.

The thickness of the coating after heat treatment depends on the use of the surface-treated stainless steel, but is usually 1 μm.
It is preferably about 2 to 2 μm, and may be peeled off if it is too thick.

[0018]

According to the present invention, a rustproof, heat resistant, water resistant, high hardness transparent coating is applied to the surface of stainless steel.
The stainless steel material is extremely useful as a material for building materials such as bathtubs and sinks, electric equipment such as reflectors of electric stoves, chemical industrial machines such as cleaning devices, medical equipment, and the like.

[0019]

【Example】

Example 1 34 g of 85% phosphoric acid diluted with 46 g of pure water was added dropwise to a mixed solution of 460 g of methyltrimethoxysilane and 460 g of isopropyl alcohol (IPA) while stirring. A silane hydrolysis / polycondensation reaction product was obtained by the exothermic reaction. This is dip-coated on mirror-polished SUS430 to form a coating film, which is dried at room temperature for 24 hours,
It was attached to the stove as a stove reflector. By igniting the stove, a cured film having a film thickness of 1 μm was formed. The SUS430 thus treated has 6
The base does not oxidize even when heated at 00 ° C, and the surface gloss,
Reflexivity was maintained for a long time.

Example 2 130 g of methyltrimethoxysilane was dissolved in 790 g of IPA, and a mixture of 34 g of 85% phosphoric acid and 46 g of water was added dropwise with stirring to obtain a silane hydrolysis / polycondensation reaction product. Spray this on SUS304,
Heat treatment was performed at 80 ° C./30 minutes, 180 ° C./60 minutes, and 300 ° C./10 minutes. SUS30 that has been treated in this way
No. 4 had excellent properties such that the base was not oxidized even after 2 hours in boiling water and a temper color was not generated due to heat during welding.

[0021]

According to the surface treatment method of stainless steel of the present invention, a transparent coating having rust resistance, heat resistance, water resistance and high hardness can be easily applied to the surface of stainless steel. INDUSTRIAL APPLICABILITY The stainless steel material according to the present invention is extremely useful as a material for building materials such as bathtubs and sinks, electric equipment such as reflectors of electric stoves, chemical industrial machines such as cleaning devices, medical equipment and the like.

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Claims (2)

[Claims] 1. A silane compound hydrolyzed and polycondensed with phosphoric acid as a catalyst is applied to the surface of stainless steel,
A method for surface treatment of stainless steel, characterized by the subsequent heat treatment. 2. The method for surface treatment of stainless steel according to claim 1, wherein the silane compound is methyltrimethoxysilane.