Effect of grain size on pitting corrosion of 304L austenitic stainless steel

• The influence of grain size on pitting corrosion is investigated.
• Grain refinement has no effect on the pitting potential.
• Frequency of metastable pit initiation decreases with grain refinement.
• Grain size reduction increases metastable pit stability.

The influence of grain size on pitting corrosion of 304L stainless steel in 3.5 wt.% NaCl solution was investigated by electrochemical methods employing the statistical approach. The potentiodynamic results revealed that grain refinement has no effect on the pitting potential. To understand the reason of ineffectiveness of grain size on pitting potential of 304L stainless steel, potentiostatic tests were conducted. Evaluation of current transients observed in potentiostatic tests revealed that the frequency of metastable pit initiation decreases with grain refinement. However, grain size reduction increases the kinetics of metastable pits dissolution and the probability of transition from metastable pitting to stability.