表面状态对核级316LN不锈钢电化学腐蚀行为的影响

Effects of surface state on the electrochemical corrosion behavior of nuclear grade 316LN stainless steel

表征了打磨态和机械抛光态316LN不锈钢表面的粗糙度、表面残余应变和表面电子功函数的分布,并研究了打磨态和机械抛光态样品在硼酸盐溶液中电化学腐蚀行为的差异.与机械抛光态316LN不锈钢相比,打磨处理后样品表面较为粗糙,且表面的微观残余应变较大,近表面产生约50μm的加工硬化层.表面粗糙度和微观应变的增加引起打磨态表面电化学活性的增大,从而促进316LN不锈钢在硼酸盐溶液中腐蚀.机械抛光处理降低了表面钝化膜的载流子密度(供体和受体),并增大了钝化膜的阻抗,提高了钝化膜的致密性和保护性,能够有效抑制金属的进一步腐蚀.

Differences between the ground and mechanically polished 316 LN stainless steel were characterized on the surface topography,surface residual strain and electron work function. The electrochemical behavior of the stainless steel was investigated in a borate buffer solution. The ground 316 LN stainless steel is featured by a rougher surface with scratches along the grinding direction.Compared with the mechanically polished sample,a thicker cold-worked layer（ ~ 50 μm） is imparted by surface grinding,indicating that the residual strain on the ground surface is much higher. The ground surface is more electrochemically active and exhibits a larger corrosion rate in the borate buffer solution,because of its rougher surface topography and a higher residual strain. The passive film on the mechanically polished sample is more compact and protective,due to the decrease of acceptor and donor density and the increase of total impedance of the passive film.