Inhibition of chloride localized corrosion of mild steel by PO43-, CrO42-,and NO2- anions

The effect of phosphate (PO43-), chromate (CrO42-), molybedate (Mo-4(2-)) a nd nitrite (NO2-) ions on the pitting corrosion of steel in 0.1 M NaCl solu tion has been studied using potentiodynamic polarization and SEM techniques . The addition of increasing concentrations of PO43-, CrO42-, MoO42- and NO 2- anions causes a shift of the pitting potential (E-pit) in the positive d irection, indicating the inhibitive effect of the added anions on the pitti ng attack. The adsorption characteristics of these anions on the steel surf ace play a significant role in the inhibition processes. The PO43--anion ha s a strong inhibitive effect of chloride pitting corrosion. The effect of d ifferent inorganic anions on the pitting corrosion of steel samples I and I I (with different composition) was also studied in 0.1 M NaCl solution. (C) 2000 Elsevier Science B.V. All rights reserved.