The main cause of corrosion in large diameter welded pipes
In fact, the reason why the large-diameter welded pipe will be rusted is mainly due to three reasons, the first is due to chemical corrosion, the second is electrochemical corrosion, and the third is due to stress concentration. Stress corrosion. Below, we will expand the analysis, hoping to help everyone better understand this issue.
First of all, let's take a look at the situation under which chemical corrosion is prone to occur, which causes corrosion of large-diameter welded pipes. The main reasons include: 1. Surface contamination. Due to the adsorption of some oil, dust, acid, alkali, salt and other substances on the surface of the pipe, it will be converted under certain conditions, resulting in chemical reaction and chemical corrosion. 2, the surface scratches, causing the protective film on the surface to be damaged; 3, after washing and passivation, the cleaning does not completely cause the residual liquid to remain, directly corroding the stainless steel.
The electrochemical factors are complex, including many reasons. The first is the contamination by carbon steel; the second is the electrochemical corrosion during the cutting process; the third is the electrochemical corrosion of the large diameter welded pipe during the welding process; the fourth is due to the existence of certain materials. The fifth defect is electrochemical corrosion due to poor pickling passivation effect.
The last case is due to the presence of concentrated stress on the surface of the large-diameter welded pipe, which causes corrosion problems due to stress.
In fact, we know that because stainless steel has good corrosion resistance, it is not prone to corrosion problems after making large diameter welded pipes. However, in some cases, corrosion problems may occur due to corrosive media and incentives.