Corrosion of stainless steel is a very complex electrochemical process, especially in the sea water environment by biological, physical, chemical and other factors. There are many anti-corrosion technologies for stainless steel. According to different sea water conditions, anti-corrosion requirements and anti-corrosion media, the adopted anti-corrosion methods are also different, and appropriate anti-corrosion methods need to be taken according to the actual situation.
The following introduces several anticorrosive methods of stainless steel.
1. Electrochemical corrosion protection
The corrosion of metals is prevented by energizing stainless steel from the outside, which is called electrochemical corrosion protection. Aluminum alloy anode with lower potential than the applied stainless steel and anti-corrosion current provided by power supply can provide anti-corrosion current, so as to prevent or reduce metal corrosion. Electrochemical anticorrosion can slow down the corrosion rate to a certain extent, and its application range is also wide.
2. Surface coating method
According to the characteristics of different types of stainless steel, the corrosion resistance of stainless steel can be significantly improved by applying matching surface coating on its surface.
By using the surface coating anticorrosion method, the corrosion can be slowed down directly or indirectly by isolating the surface coating, refining the surface grain and improving the hardness. The surface coating is all physical coating. Although physical coating can effectively improve the corrosion resistance, it is also vulnerable to external factors, so the stability is not very high.
3. Solution treatment of stainless steel weldment
Optimization of welding process and heat treatment process can significantly improve the resistance of stainless steel to intergranular corrosion and pitting corrosion after welding, and enhance the stability of passive film to a certain extent. The solution treatment of stainless steel welding joint can effectively improve the sensitization and stress corrosion resistance of the welding joint.
4. Optimize stainless steel processing technology
Different processing technologies of stainless steel have great influence on the corrosion resistance of stainless steel. If the process can be optimized and the alloy ratio can be controlled during the processing, the corrosion resistance of stainless steel can be effectively improved. Bright annealing of stainless steel can reduce the white noise level, increase the size of impedance mode and make the passivation film more stable. The sensitization temperature can change the diffusion rate of Cr, thus affecting the intergranular corrosion. The higher the sensitization rate is, the faster the diffusion rate is and the more serious the intergranular corrosion is.
Through comparison, it is found that there are many ways to improve the corrosion resistance of stainless steel, but the application conditions of different methods are also different. In the actual process, one or several methods should be used to improve the corrosion resistance of stainless steel.