JPS6031899B2 - Method for preventing corrosion and stress corrosion cracking on metal surfaces and inhibiting their progress - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to preventing and inhibiting the corrosion and stress corrosion cracking of metal surfaces.

Various studies have been conducted on countermeasures to prevent corrosion and stress corrosion cracking, including heat treatment to relieve stress, application of shot vinyl sogs, addition of corrosion inhibitors, pH adjustment, cathodic protection, use of aluminum cladding materials, etc. Furthermore, improvement measures are being considered, such as the application of the Linisog method and passive treatment method for environmental isolation, as well as material changes, equipment design changes, process changes, and equipment expansion.

There are many factors that can cause corrosion and stress corrosion cracking in practical equipment, including environmental conditions, manufacturing and processing conditions, location conditions for equipment installation, stray current, and the lot used for equipment base materials, and it takes a long time to take countermeasures and treatments. As a result, the equipment is often disposable. Corrosion and stress corrosion cracking problems often occur even if they are thoroughly considered at the design stage, and are often discovered during periodic inspections and prompt countermeasures must be taken. The present invention was developed in view of the above-mentioned circumstances, and its purpose is to apply shot blasting and grit blasting to impart compressive stress and create a sludge surface, and then to apply base thermal spraying, finishing thermal spraying, and sealing. The present invention provides a method for preventing and slowing the progression of metal surface corrosion and stress corrosion cracking by forming a laminated film through hole treatment. The method for preventing and inhibiting corrosion of metal surfaces and stress corrosion cracking according to the present invention will be described below with reference to Examples. Example 1 1st process Shot 2nd process Grit blasting 3rd process Nickel aluminide twill spraying 4th process Aluminum thermal spraying 5th process Example 2 of sealing treatment with silicone resin 2 1st process Shot 2nd process Grit blasting 3rd process Processes Nickel-based alloy thermal spraying 4th process Titanium thermal spraying 5th process In the first process of sealing with epoxy resin, the metal surface is blasted with a shot material such as rusted steel or cast iron.

This cleans the metal surface, simultaneously beaning it, hardening it, and imparting compressive stress. In the second step, blasting is performed with a blasting material such as aluminum or lenium carbide to roughen the metal surface. The corrosion potential of the plasted surface is higher than that of the base metal, making the entire surface more susceptible to corrosion and pitting corrosion less likely to occur. Also, the roughening of the surface improves the adhesion of the twill coating. Immediately after grit blasting, the third step is base thermal spraying. In Example 1, nickel aluminide is thermally sprayed as a base thermal spray for the purpose of increasing adhesion strength and secondary corrosion protection. In Example 2, a nickel-based alloy is used as the base thermal spray material. The base thermal spray material is selected in consideration of adhesion and corrosion resistance. After the base coat is sprayed, finish spraying is carried out. In Example 1, aluminum thermal spraying is performed as finishing thermal spraying. Aluminum spray coatings exhibit sacrificial corrosion protection effects. In Example 2, titania thermal spraying is performed.
By performing pore sealing treatment after thermal spraying, the film becomes a completely environmentally sealed film. Titania coating has excellent wear resistance and corrosion resistance. Alumina thermal spraying may also be used as a finishing solvent, and as a final step, after the finishing thermal spraying, hole treatment is performed using a base resin, epoxy resin, bituminous material, paraffin, etc. The sealing treatment is carried out within the time period during which the finish thermal spray coating remains active. The pores in the film are sealed by the penetration of the sealing agent through capillary action. Aluminum coatings often act as sacrificial coatings, so the presence of pores in the coating does not pose a problem, but nickel-based alloy coatings often have a corrosion potential lower than that of the base material (carbon steel). It must be completely isolated from the environment, and special attention must be paid to sealing. As mentioned above, the method for preventing and inhibiting corrosion and stress corrosion cracking on metal surfaces of the present invention consists of five steps: a shot step, a grit blasting step, a base thermal spraying, and a sealing treatment, and not one step can be omitted. .

In the present invention, the first and second steps, which are pre-treatments, have the effect of relieving stress and increasing the adhesion strength by forming a sludge surface, and the metal surface is completely shielded from the corrosive environment by the pore-sealing thermal spray coating. However, the synergistic effect of blasting and thermal spray coating prevents and inhibits corrosion and stress corrosion cracking. That is, by blasting, compressive stress is applied to the metal surface to relieve the stress or residual stress applied to the structural material. Then, in order to protect the blasted metal surface from corrosion, a thermal spray coating is applied as described above. The present invention is characterized by the discovery of the above-mentioned combination out of many combinations of surface treatment methods, and is extremely effective in preventing corrosion and stress corrosion cracking of stainless steel, carbon steel, etc. and inhibiting their progress. It is effective.

Claims (1)

[Claims] 1. In a metal surface corrosion prevention method comprising the steps of blasting with grit material, thermal spraying, and sealing, a step of blasting with shot material is performed before the grit blasting step, and A method for preventing corrosion and stress corrosion cracking on metal surfaces and inhibiting their progress, which comprises performing a thermal spraying process of base thermal spraying with a nickel-based alloy and a final thermal spraying process of aluminum, titanium, or alumina.