2205双相不锈钢临界点蚀温度的测定

Study of Test on Critical Pitting Temperature on 2205 Duplex Stainless Steel

依据ASTM G48标准试验方法对某天然气管道工程应用的2205双相不锈钢钢管的临界点蚀温度进行了测定,并且对产生点蚀的现象和原因进行了研究。结果表明该钢管材料的CPT为38℃,点蚀分为2种发展趋势(点蚀坑的形貌分为2种):第1种是表面张开型蚀坑,氯离子在试样表面聚集,形成蚀核并向其周边生长在试样表面形成光滑的腐蚀形貌;第2种是表面封闭性蚀坑,是由于材料表面局部钝化膜破坏,氯离子通过优先发生点蚀的区域向内部渗透,在试样表层下面形成高氯离子区,随后腐蚀区域慢慢增大,形成腐蚀空洞。

Acconting to ASrM G48 standard test method,we tested the critical pitting temperature （CPT） on 2205 duplex stainless steel used in some nature gas pipeline projects and studied the phenomenon and reason of pitting. The result showed the CPT was 38℃, and pitting has two kinds of development trends （The shape of pitting had two kinds）.The first kind is that the surface of the pitting is open. assembling on the sample surface of chlorine ion form pitting cores and grow around it, at smooth corrosion shape is finally formed on the sample surface.The second kind is that the surface of the pitting is closed, because some passivation of the surface is destroyed. The chlorine ion permeates the inside through having priority pitting area. The chlorine ion assembled under the sample top layer, soon afterward the pitting area increased slowly and some cavities were formed.