Effect of scale formation and CP potentials on AC-induced pitting corrosion of low carbon steels

摘要

The effect of AC voltages, cathodic protection (CP) potentials and calcareous scale on the pitting corrosion of carbon steel 1010 was investigated by potentiostatic tests, electrochemical impedance spectroscopy (EIS) measurements and surface characterization techniques. Under the CP potential of - 1.12 V-SCE, pitting corrosion increased with increasing AC voltage due to higher DC and AC current densities. The highest pitting severity was found at the highest AC current density over 4000 A/m(2), facilitated by the utilization of microelectrodes. The presence of calcium and magnesium deposits reduced the pitting severity for all AC conditions acting as a barrier on the steel surface. Under constant high AC voltage, the dominant form of corrosion (uniform vs. pitting) depended on the applied CP potential and lowering the CP potential to - 1.5 V-SCE promoted greater metal dissolution. It was also found that the presence of AC interference was not necessary for pit initiation, but it promoted pit growth. [GRAPHICS] .