普查了国内某海滨核电站核燃料厂房(K厂房)不锈钢管道的腐蚀情况和Cl-浓度, 发现K厂房不锈钢管道存在普遍的腐蚀问题, 腐蚀主要发生在弯管和焊缝部位, 以点蚀为主, K厂房大气中Cl-含量是现场大气环境中的18倍左右。采用自行设计的装置预制点蚀坑, 用恒载荷法研究了溶液中304L不锈钢由点蚀扩展为应力腐蚀的行为过程; 结果表明, 304L不锈钢发生应力腐蚀门槛应力在80% Rp0.2左右, 1级椭圆形点蚀坑扩展为SCC的Cl-临界浓度在5~10 mg/L之间。根据现场调查和试验结果推断, K厂房奥氏体不锈钢管道在含有氯离子的大气中应力腐蚀开裂(SCC)过程可分为两个阶段, 先是金属表面钝化膜被破坏而发生点蚀, 以后以蚀坑底部的敏感点为裂纹源, 扩展为SCC。

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.