检验不锈钢非敏化态晶间腐蚀敏感性的新方法

A New Technique for Detecting the Susceptibility to Intergranular Corrosion of Non-Sensitised Stainless Steels

采用恒电位浸蚀法配合以金相方法,研究了尿素级316L不锈钢非敏化晶间腐蚀的发展规律,比较了不同浸蚀介质、控制电位和浸蚀时间等因素的影响,结果表明:过钝化区恒电位浸蚀法可以快速、灵敏地检测奥氏体不锈钢的非敏化晶间腐蚀敏感性,使用超低磷、硅不锈钢可以减轻或消除非敏化晶间腐蚀,实验推荐下列二种检验操作条件:(1)10％草酸+0.2％KSCN溶液,30℃;浸蚀电位1.125V(SCE);30min.(2)20％H_2SO_4+2％NaCl+0.2％KSCN溶液,30℃;1.140V(SCE);30min。

The behavior of non-sensitized intergranular corrosion (IGC) for urea grade316L stainless steel (SS) was studied by using the method of the potentiostatic etching in thetranspassive potential region and the metallograph. The etching parameters were comparedas well. It was found that the susceptibility of SS to non-sensitized IGC can be detectedquickly and sensitively by the method of transpassive potentiostatic etching.Two etchingconditions were given: (1) in etching electrolyte of 10% oxalic acid +0.2%KSCN at tem-perature of 30℃ and potential of 1.125V (SCE) for 30 min; and (2) in etching electrolyteof 20% H_2SO_4+2% NaCl+0.2% KSCN at temperature or 30℃ and potential of 1.140 V(SCE) for 30 min. After etching, the measurement of the width of corroded grain bounda-ry region instead of IGC depth was recommended to evaluate the degree of susceptibility tonon-sensitized IGC.