Crevice corrosion kinetics of nickel alloys bearing chromium and molybdenum

The crevice corrosion kinetics of alloys C-22, C-22HS and HYBRID-BC1 was studied in several chloride solutions at 90 °C. The crevice corrosion resistance of the alloys increased with PREN (Pitting Resistance Equivalent Number), which is mainly affected by the Mo content in the alloys. The crevice corrosion kinetics of the three alloys was analyzed at potentials slightly higher than the repassivation potential. Crevice propagation was controlled by ohmic drop in the more dilute chloride solutions, and by charge transfer in the more concentrated chloride solutions. Ohmic drop was not a necessary condition for crevice corrosion to occur.

► The crevice corrosion resistance of the tested alloys increased with PREN, which is mainly affected by their Mo content.
► Crevice corrosion kinetics was controlled by ohmic drop only in the more dilute chloride solutions.
► Charge transfer control was observed in concentrated chloride solutions.
► A critical ohmic drop was not necessary for crevice corrosion to occur.
► Ohmic drop was a consequence of the crevice corrosion process in certain conditions.