A microelectrochemical approach to understanding hydrogen absorption into steel during pitting corrosion

A small Devanathan-Stachurski cell was newly designed to ascertain the hydrogen absorption behavior into re-sulfurized carbon steel during pitting corrosion. In 0.1 M NaCl (pH 5.5), a pit was generated on a small area with MnS inclusions, the current of hydrogen permeation current increased sharply when the solution (capillary) was placed on the steel surface, and the current density returned to the background after the capillary was removed. On the other hand, no pitting was observed on the area without the inclusions, and no permeation current was also observed. The time variation of the permeation current density was measured in 0.1 M NaCl (pH 2.0) and boric-borate buffer with 1 mM NaCl (pH 5.5) solutions. The permeation current from a small area with MnS inclusions was large compared with that of an area without the inclusions. After the experiments, a deep pit was generated on the surface with the inclusions. MnS inclusions were likely to accelerate the steel dissolution and the hydrogen absorption into the steel.