After the research and study, experts have found there are three necessary conditions causing Stress Corrosion Cracking (SCC for short):
1、Austenitic stainless steel has sensitivity to SCC.
2、Residual stress existed inside material after welding and cold work.
3、Concentration condition of CL-ion content in hot water with the temperature of 50-100。C.
When the above three conditions provided at the same time, then stress corrosion occurs, on the opposite, if one condition among the three is destroyed by us, it is able to overcome the cracking caused by stress corrosion.
-Mechanism of CL- pitting corrosion destruction
As we all know, solubility of CL-ion in water is decreased as the reduction of pressure. Therefore, once CL- tap water with the pressure of 5kg/cm2 in the pipe flows into water tank, the pressure is reduced by 0, which make a lot of redundant CL-ion in liquid phase volatilized into gas phase and condensed in tiny drops. CL-ion content in experiment drops is 300~400 times higher than the CL-ion content in liquid phase, which causes CL-ion pitting corrosion in gas phase and form perforation destruction |
