Influence of Cl- on Development Behavior from Pitting Corrosion to Stress Corrosion Cracking of 304L Stainless Steel

Corrosion conditions and Cl- concentrations were generally surveyed in K factory of a nuclear power plant. The results indicated that corrosion problems, especially pitting corrosion, occured the surface of stainless steel pipeline in K factory and mainly occured in elbow pipe and weld pipe. And, the Cl- concentration in the atmosphere of K factory was about 18 times of that of the surrounding atmospheric environment. A new instrument was designed to make corrosion pit. Constant stress method was applied to study the development behavior from pitting corrosion (PC) to stress corrosion cracking (SCC) of 304L stainless steel. The results showed that the sensitivity stress of SCC for 304L was around 80% Rp0.2. The critical Cl- concentrations of expansion behavior from PC with an oval pit to SCC was 5~10 mg/L. SCC of stainless steel pipeline in K factory in Cl- atmosphere could be divided into two stages. The first stage was PC, then SCC.