Crevice corrosion behavior of X70 steel in NaCl solution with different pH

The crevice corrosion of X70 steel in 0.34 mol/L NaCl solution with different pH was investigated. The crevice corrosion could be initiated in pH = 2 and pH = 12 solution and it could not occur in pH = 6.8 solution. The increase of pH and Cl- inside crevice are responsible to crevice corrosion in pH = 2 solution. However, the decrease of pH and increase of Cl- inside crevice contribute to crevice corrosion in pH = 12 solution. The negative shift of OCP of steel outside crevice results in the disappearance of galvanic corrosion and then crevice corrosion could not occur in pH = 6.8 solution.

Automated summary

The crevice corrosion of X70 steel varies in different pH solutions, with pH=2 and pH=12 solutions promoting crevice corrosion while pH=6.8 solution prevents it. The increase of pH and Cl- inside crevice contribute to crevice corrosion in pH=2 solution, while the decrease of pH and increase of Cl- inside crevice lead to crevice corrosion in pH=12 solution.