Formation of Ferrous Sulfide Film from Sulfite on Steel Under Anaerobic Conditions

The reactions of carbon steel and sulfite ions were studied by electrochemical experiments in 0.5 M NaCl solution under anaerobic conditions. Sulfite was reduced to sulfide, and a black ferrous sulfide film was formed. The process was monitored as a function of time at different potentials. During film formation, the current density and the intensity of reflected light from the steel surface were recorded. The film formation followed initially a 2-dimensional model and later a 3-dimensional model. The rate of film formation was studied as a function of ionic concentration, electrode rotation speed, potential, and the surface-roughness of the electrode.