JP3129838B2 - Metal corrosion protection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for preventing corrosion of metals.

[0002]

2. Description of the Related Art As a method for preventing corrosion of a metal material, there are a method of coating the surface with an organic material or an inorganic material, a method of adding a corrosion inhibitor to a corrosive environment, and a method of electrolytic protection.

[0003] Among the methods of coating a surface, the application of an organic material involves coating a metal surface with a polymer compound and simply isolating the metal material from a corrosive environment, and corrosion occurs from a pinhole or the like in the coating film. There was a problem and I was not always satisfied. Further, the lining is thicker than the coating, and is superior in anticorrosion performance. However, since the lining is inferior in workability, the lining is limited in the application field, and has a problem that corrosion occurs from pinholes or the like.

[0004] Corrosion inhibitors for corrosive environments include:
Amines and the like. The corrosion inhibitor is effective when added in a small amount to a corrosive medium such as a circulating cooling system, a water system for a boiler, or various storage tank systems, and has a problem that its application field is naturally limited.

[0005] Further, it is known that a cathodic protection method for artificially controlling the potential of a metal material exhibits excellent effects in a strongly corrosive environment. However, it is a method of connecting an external power supply or connecting a sacrificial pole for anodic polarization or cathodic polarization, and technical and economic difficulties such as the need for a reliable device to control the potential. Is accompanied.

In order to improve these problems, there is a report on a simple anticorrosion method using an electrically active substance. For example, it has been reported that an anti-corrosion effect in a sulfuric acid solution or a sulfuric acid solution containing chloride ions by coating a stainless steel surface with an electrically active polyaniline film [David W DeBer.
ry), "Journal of Electrochemical Society" (J. Electrochem. So
c. ,) Vol. 132, (1985) p. 1022]. This method is simple and does not require a special device or the like, and has an excellent anticorrosion effect. However, to form a polyaniline film on the stainless steel surface by electrolytic polymerization,
There are problems such as the necessity of a large electrolytic polymerization facility when applied to a large area or a large structure. Also,
The polyaniline film formed by electrolytic polymerization contains, as a dopant, an anion from a supporting electrolyte or a protonic acid.

[0007] Also, JP-A-63-199884 describes that
An anticorrosion method is disclosed in which a paste-like mixture of powdered polyaniline and polyvinyl chloride dissolved in tetrahydrofuran is applied to the surface of an iron pipe and dried. However, the powdered polyaniline in the paste mixture is insoluble in the solvent and is merely dispersed.Even if this mixture is applied, the powdered polyaniline is only dispersed unevenly in the polyvinyl chloride film. Cannot be uniformly coated with powdered polyaniline, and the anticorrosion effect is insufficient.
In addition, the powdered polyaniline contains, as a dopant, a proton acid from an oxidizing agent during chemical polymerization.

When a polyaniline-based compound containing a dopant such as an anion or a protonic acid from a supporting electrolyte or an oxidizing agent is applied to a metal surface, the polyaniline-based compound exhibits an anticorrosive effect due to the oxidation-reduction action of the compound. Certain anions or protonic acids themselves tend to cause corrosion, and improvements have been desired.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, prevent corrosion caused by dopants, exhibit an excellent anticorrosion effect even in a strongly corrosive environment, and require a special device. Another object of the present invention is to provide a method for preventing corrosion of a metal which is simple and can be applied to a large area or a large structure.

[0010]

Means for Solving the Problems As a result of various studies, the present inventors have found a method for preventing metal corrosion that has solved the above-mentioned problems, and have completed the present invention.

That is, the present invention is characterized in that a metal surface is dipped or coated with a solution containing a soluble polyaniline-based compound containing no dopant and then dried to form a film of the polyaniline-based compound containing no dopant. Anticorrosion method, or dipping or coating the metal surface with a solution containing a soluble polyaniline-based compound and a general-purpose polymer compound containing no dopant and drying to form a composite film of a polyaniline-based compound and a general-purpose polymer compound containing no dopant It is a method of preventing corrosion of metal.

Hereinafter, the present invention will be described in detail.

The polyaniline-based compound containing no dopant used in the present invention is an oxidized polymer of aniline or a derivative thereof and is soluble in a solvent.

The aniline derivative used in the present invention is obtained by substituting the N-position, 2-position or 3-position of aniline with an alkyl group or an alkoxy group or the like, and includes N-methylaniline, N-ethylaniline, N-propylaniline. , N-
N-alkylanilines such as butylaniline, N-pentylaniline, N-hexylaniline, N-heptylaniline or N-octylaniline, o-toluidine,
2-alkylaniline such as 2-ethylaniline, 2-propylaniline, 2-butylaniline, 2-pentylaniline, 2-hexylaniline, 2-heptylaniline or 2-octylaniline; m-toluidine;
3-alkylaniline such as ethylaniline, 3-propylaniline, 3-butylaniline, 3-pentylaniline, 3-hexylaniline, 3-heptylaniline or 3-octylaniline, or 2-methoxyaniline, 3-methoxyaniline, -Alkoxyanilines such as ethoxyaniline.

The oxidized polymer of aniline or a derivative thereof used in the present invention may be a copolymer thereof.

The soluble polyaniline-based compound containing no dopant used in the present invention is electrically active,
Since each oxidation-reduction potential is constant, when a film is formed on the metal surface, the potential of the metal is kept constant and an excellent anticorrosion effect is exhibited.

As a dopant for the polyaniline compound, a strong acid such as a mineral acid or a sulfonic acid is generally used, and these acids or anions tend to cause corrosion of the metal. In the present invention, since a soluble polyaniline-based compound containing no dopant is used, the anticorrosion effect is further excellent.

The general-purpose polymer compound used in the present invention is a synthetic resin such as a thermosetting resin or a thermoplastic resin, a synthetic rubber, a natural polymer or an inorganic polymer, and is polyethylene, polypropylene, polystyrene, polycarbonate, polymethyl, or the like. Methacrylate, polyester, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl formal, polyamide, polyimide, epoxy resin, phenol resin, silicone resin, fluororesin, nylon, vinyl chloride-vinyl acetate copolymer, acrylonitrile -Styrene copolymer, acrylonitrile-butadiene-styrene copolymer or silicon resin. These can be used alone or in combination. The general-purpose polymer compound is used by being dissolved in a solvent together with a soluble polyaniline-based compound containing no dopant.

The solvent used in the present invention is not particularly limited as long as it dissolves a soluble polyaniline compound containing no dopant, a soluble polyaniline compound containing no dopant, and a general-purpose polymer compound.

In the present invention, the formation of the film is performed by coating the metal surface with
A solution containing a soluble polyaniline-based compound containing no dopant or a solution containing a soluble polyaniline-based compound containing no dopant and a general-purpose polymer compound. It can be easily done just by drying. A solution that contains a soluble polyaniline-based compound containing no dopant and adheres to the metal by simply immersing, coating, and drying, but is immersed, coated, and dried in a solution containing a soluble polyaniline-based compound and a general-purpose polymer compound that do not contain a dopant However, the adhesion can be further strengthened, and the metal surface can be uniformly coated with the polyaniline-based compound.

According to the metal anticorrosion method of the present invention, a film of a polyaniline-based compound containing no dopant or a composite film of a polyaniline-based compound containing no dopant and a general-purpose polymer compound is formed on the metal surface, and then formed thereon. When coating with organic or inorganic materials, etc.
Corrosion environment can be cut off, and the anticorrosion effect is further improved.

[0022]

Hereinafter, the present invention will be described with reference to Synthesis Examples and Examples, but the present invention is not limited to these Synthesis Examples and Examples.

Synthesis Example 1 150 g of water and 10.1 g of concentrated hydrochloric acid were added to 9.3 g of aniline, and a solution prepared by dissolving 22.8 g of ammonium persulfate in 40 g of water was added dropwise over 2 hours while maintaining the temperature at 0 to 10 ° C. And stirred for 3 hours. Then, 41g of concentrated ammonia water
Was added dropwise in 1 hour, and the mixture was further stirred for 5 hours.
After repeating washing with water and washing with methanol, vacuum drying was performed to obtain 8.3 g of polyaniline containing no copper-colored dopant. The obtained copper-colored dopant-free polyaniline was dispersed in 200 ml of methanol, 20 g of hydrazine-hydrate was added, and the mixture was stirred at room temperature for 15 hours, filtered, washed with water and methanol, and dried in vacuo. 7.5 g of soluble polyaniline containing no grey-blue dopant were obtained. N-methyl- so that the content of polyaniline is 5 wt%.
Dissolved in 2-pyrrolidone to obtain a polyaniline solution containing no dopant. The solution was diluted with water, made alkaline with aqueous ammonia, filtered to remove insolubles, and then analyzed by ion chromatography. As a result, no anion was detected, and it was confirmed that no dopant was contained.

Synthesis Example 2 Soluble poly- (2-ethylaniline) containing no dopant was prepared in the same manner as in Synthesis Example 1 except that 12.1 g of 2-ethylaniline was used instead of aniline. 1 g was obtained. Poly- (2-ethylaniline) 5
It was dissolved in N, N-dimethylformamide so as to be wt% to obtain a poly- (2-ethylaniline) solution containing no dopant.

Example 1 A 0.5 mm-thick iron plate (25 mm long × 25 m wide) was placed on the polyaniline solution containing no dopant obtained in Synthesis Example 1.
m, manufactured by Aldrich) and then immersed in
After drying for an hour, a dark blue dopant-free polyaniline film was formed on the iron plate. After making a 1cm length scratch on the film with a cutter, 5wt% saline or 5wt%
After immersion in 2% hydrochloric acid for 2 weeks, no corrosion was observed in both.

Example 2 In Example 1, in place of the dopant-free polyaniline solution obtained in Synthesis Example 1, 50 g of the dopant-free polyaniline solution obtained in Synthesis Example 1, an epoxy resin (Epicoat 828 (oil Shell epoxy (registered trademark) and 1.7 g of an epoxy resin curing agent (epomate C-002 (oiled shell epoxy (registered trademark))) in the same manner as in Example 1 except that a solution of 1.7 g was used. After forming a composite film of polyaniline and epoxy resin containing no dopant on an iron plate, a corrosion prevention test was carried out in the same manner as in Example 1, but no corrosion was observed.

Example 3 In the same manner as in Example 2, after forming a composite film of polyaniline and epoxy resin containing no dopant on an iron plate, 50 g of epoxy resin (Epicoat 828) and a curing agent (Epomate C-002) were used. After 25 g of the mixed solution was brush-coated, heated and cured at a temperature of 130 ° C. for 3 hours, an anticorrosion test was carried out in the same manner as in Example 1, but no corrosion was observed.

Example 4 In Example 1, the dopant-free poly- (2-ethylaniline) obtained in Synthesis Example 2 was used instead of the dopant-free polyaniline solution obtained in Synthesis Example 1.
50 g of the solution, epoxy resin (Epicoat 1001-T-
75) 3.5 g and epoxy resin curing agent (Epomate S
-005) In the same manner as in Example 1 except that 1.5 g of the solution was used, poly- (2
After forming a composite film of (-ethylaniline) and an epoxy resin, an anticorrosion test was performed in the same manner as in Example 1, but almost no corrosion was observed.

Example 5 The procedure of Example 1 was repeated, except that a stainless steel plate having a thickness of 2 mm (length 60 mm × width 25 mm, SUS304) was used instead of the iron plate. After forming a film of polyaniline, ferric chloride 100 was added to 900 ml of N / 20 hydrochloric acid solution.
g in a solution of 6 wt% ferric chloride acidified with hydrochloric acid at a temperature of 3
After immersion at 5 ° C. for 3 days, no weight loss of the stainless steel plate was observed.

Example 6 The procedure of Example 1 was repeated, except that a stainless steel plate having a thickness of 2 mm (length 60 mm × width 25 mm, SUS316) was used instead of the iron plate. After forming the polyaniline film, an anticorrosion test was carried out in the same manner as in Example 5, but no weight loss of the stainless steel plate was observed.

Example 7 The procedure of Example 2 was repeated, except that a 0.5 mm thick titanium plate (30 mm long × 20 mm wide) was used in place of the iron plate. After forming a composite film of polyaniline and epoxy resin, a corrosion prevention test was performed in the same manner as in Example 1, but no corrosion was observed.

Example 8 A cold-rolled steel plate having a thickness of 1 mm (width 760 mm × length 1800)
mm, SPCC equivalent product) and a dopant-free polyaniline solution 600 obtained in the same manner as in Synthesis Example 1.
g, polyurethane resin (trade name: Olestar NL224)
9E, a mixed solution of 100 g of Mitsui Toatsu Chemical Co., Ltd.) and 200 g of methyl cellosolve acetate is applied by spraying and dried at a temperature of 100 ° C. for 15 minutes to form a composite film of polyaniline and polyurethane resin containing no dopant on a steel plate. After the formation, it was immersed in a 3 wt% saline solution at a temperature of 60 ° C. for 6 months to conduct an anticorrosion test, but no corrosion was observed. Although a large electrolytic tank is required to form a polyaniline film by electrolytic polymerization, this method is simple simply by spraying.

Comparative Example 1 An epoxy resin (Epicoat 828) 5 was placed on a 0.5 mm-thick iron plate (25 mm long × 25 mm wide, manufactured by Aldrich).
After brush-coating a mixture of 0 g and 25 g of a curing agent (Epomate C-002), the mixture was heated and cured at a temperature of 130 ° C. for 3 hours, and then subjected to an anticorrosion test in the same manner as in Example 1. Rust was generated with a width of several mm.

Comparative Example 2 150 g of water and 10.1 g of concentrated hydrochloric acid were added to 9.3 g of aniline, and a solution in which 22.8 g of ammonium persulfate was dissolved in 40 g of water was added dropwise over 2 hours while maintaining the temperature at 0 to 10 ° C. And stirred for 3 hours. Thereafter, the mixture was filtered and dried to obtain 8 g of powdered polyaniline. Ammonia water was added to the obtained powdery polyaniline, and the mixture was stirred, filtered, and the filtrate was analyzed by ion chromatography. As a result, HSO ₄ ⁻ and Cl ⁻ were detected. This indicates that the polyaniline powder contains HSO ₄ ⁻ and Cl ⁻ or an acid composed thereof as a dopant. 5 g of the obtained powdered polyaniline, polyvinyl chloride (Wako Pure Chemical Industries, Ltd.)
5 g) and 50 g of tetrahydrofuran were mixed to obtain a powdered polyaniline dispersion.

In Example 1, powdered polyaniline and polyvinyl chloride were prepared in the same manner as in Example 1 except that the dispersion of the powdered polyaniline was used instead of the polyaniline solution containing no dopant obtained in Synthesis Example 1. After the formation of the composite coating of Example 1, an anticorrosion test was carried out in the same manner as in Example 1. As a result, rust was generated on the surface of the iron plate.

[0036]

According to the anticorrosion method of the present invention, a uniform and smooth coating of a polyaniline-based compound containing no dopant or a polyaniline-based compound containing no dopant and a general-purpose polymer compound can be obtained by simply dipping or coating a metal surface with a solution. A composite coating is formed. Further, since a dopant that contributes to corrosion is not contained, the metal material treated by the anticorrosion method of the present invention exhibits an excellent anticorrosion effect even in a strong corrosive environment containing salt, hydrochloric acid, or the like. Further, a film can be formed on a large-area metal material or structure by a simple method such as spraying.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-199884 (JP, A) JP-A-57-177978 (JP, A) JP-A-3-272514 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C23F 11/00 C23F 15/00 C23F 13/00

Claims (2)

(57) [Claims] 1. A method for preventing corrosion of metals, comprising immersing or coating a metal surface with a solution containing a soluble polyaniline-based compound containing no dopant and drying it to form a film of the polyaniline-based compound containing no dopant. 2. A metal surface is immersed or coated in a solution containing a dopant-free soluble polyaniline compound and a general-purpose polymer compound, and dried to form a composite film of the dopant-free polyaniline compound and a general-purpose polymer compound. A method for preventing metal corrosion.