Changes in pitting corrosion parameters of 316 L stainless steel for two potentiodynamic polarization modes

The influences of repeated polarization on the pitting parameters of 316 L stainless steel in 0. 01 mol/L NaCl solution have been studied using slow rate potentiodynamic polarization. The tests were carried out under two different conditions: in condition A,the first polarization was stopped before stable pitting occurred; in condition B,the first polarization was stopped after stable pitting occurred. Then the second polarization was run to determine the influence of the metastable pits and stable pits formed during the first polarization on the subsequent pitting process. The results show that the two initial polarization conditions have little impact on pitting corrosion behavior during the second polarization. Under both conditions,the first polarization reduced the active points on the material surface and led to decreased nucleation rate of metastable pitting,and both the metastable pitting potential E m and stable pitting potential E b increased. Compare with the initial polarization,the peak current and the average growth rate of metastable pits in the second polarization increased,which may be attributed to the higher polarization potential range during the second polarization.