Corrosion inhibition of mild steel by sodium tungstate in neutral solution Part 1: Behaviour in distilled water

Abstract

The inhibition of corrosion of mild steel in aqueous solutions by sodium tungstate (Na₂WO₄) has been studied in oxygen saturated, freely aerated, and fully deaerated solutions. Open circuit potential measurements were complemented by visual examination of the specimens. Curves of steady state potential versus log inhibitor concentration were constructed which revealed domains of corrosion and of passivation. It is argued that both O₂ and WO²⁻ ₄ are physically adsorbed on the metal surface. Inhibition by WO²⁻ ₄ necessitates the presence of this ion and O₂ simultaneously in solution and the formation of an ordered arrangement of the two species on the surface. Electrochemical measurements show that there is a direct relationship between the corrosion rate and the corresponding steady state potential.