ELECTROOXIDATION OF 1024-MILD-STEEL IN SLIGHTLY ALKALINE PHOSPHATE AND BICARBONATE SOLUTIONS

The electrochemical behaviour of 1024 mild steel electrodes was invest igated in the presence of 0.05-0.5 M disodium phosphate aqueous soluti on, in the pH range 8.4 to 9.7 and from 5 to 50 degrees C. Bicarbonate solutions were also considered for comparison. Voltammograms were obt ained with a rotating gold ring steel disc electrode, and the effects of the phosphate concentration, pH, electrode rotation speed, anodic p otential limit and temperature were considered. For potential sweeps i n the anodic direction in phosphate solutions, the voltammograms displ ay an oxidation peak current at low potentials and a passivity region at higher potentials. The rate-determining step of the oxidation peak current was also investigated. The oxidation current in the passivity region is virtually independent of the applied potential, temperature, pH and phosphate concentration.