利用等通道转角挤压(ECAP)方法, 制备出平均晶粒尺寸为(130±30) nm的块体超细晶304L不锈钢. 在0.05 mol/L H₂SO₄+0.25 mol/L Na₂SO₄溶液中测量了其极化曲线和钝化性能的Mott-Schottky曲线.结果表明, 与粗晶合金相比, 超细晶材料的自腐蚀电位更低, 自腐蚀电流密度更大, 更易发生活性溶解且溶解速度更快, 但致钝电位更低, 维钝电流密度更小, 钝化区间更宽. 表面钝化膜均具有n型半导体特征,超细晶粒有助于304L不锈钢表面形成更为稳定的钝化膜, 载流子密度更小, 载流子的扩散系数更低.

 Samples of ultrafine-grained 304L stainless steel with an average grain size of (130±30) nm wereprepared by using equal channel angular pressing (ECAP) technique after 6 passes with route Bc at 500 ℃.The electrochemical behaviors and the passive properties of the material in 0.05 mol/L H₂SO₄+0.25 mol/L Na₂SO₄solution were examined by using polarization curves and Mott-Schottky analysis. As compared with the coarse-grained counterpart, the ultrafine-grained 304L stainless steel sample exhibits a lower corrosion potential(-505 mV) and a higher corrosion current density (11.7μA/cm²), indicating the accelerated trend of the activedissolution, and has a broadening of passive region (-341-847 mV) with lower passive potential (-341 mV) andpassivation current density (4.5μA/cm²). Both of the passive films exhibit n-type semi-conductor behaviorsat potentials ranging from 0 to 0.7 V. The ultrafine grains of 304L stainless steel are helpful in forming more stablepassive films with the reduced donor density and the diffusion coefficient of the charge carrier.