2020 Volume 69 Issue 2 Pages 49-57
When crevice corrosion of stainless steel occurs and progresses, the proton and the chloride ion concentration is high and there is no dissolved oxygen in the crevice. On the other hand, when crevice corrosion of stainless steel stops, the proton and the chloride ion diffuses out of the crevice and dissolved oxygen penetrates the inside of the crevice. In this case, the state of the stainless steel changes from active state to passive state.
Since it is important to know the passivation behavior of the stainless steel, we invest the effect of chloride ion and dissolved oxygen concentration on passivation pH of SUS304 stainless steel.
The passivation pH of SUS304 steel increased with increasing chloride ion concentration and decreasing dissolved oxygen. When cathodic current density exceeds ICRIT, passivation occurs.
Therefore, It is assumed that the rise of ICRIT and the decrease of cathodic current density of the proton reduction with the rise of chloride ion concentration and the decrease of cathodic current density of the oxygen reduction with the decrease of dissolved oxygen concentration contributes to increasing passivation pH.
