Inhibition of steel pitting corrosion in HCl by some inorganic anions

The effect of Mn and V content on corrosion behavior of mild steel in different concentration of HCl was investigated. The increase of Mn and V content in the steel sample leads to increasing corrosion resistance. The effect of phosphate, molybedate and chromate anions on the corrosion of steel in HCl solution has been studied using weight loss, potentiodynamic and scanning electron microscope (SEM) techniques. The addition of increasing concentrations of phosphate, molybedate and chromate anions causes a shift of the pitting potential (Epit) in the positive direction, indicating the inhibitive effect of the added anions on the pitting attack. The phosphate anion has a stronger inhibitive effect of the pitting corrosion. The inhibition efficiency (IE) of different inhibitors increases with the increasing of phosphate concentration and decreases with the increasing the concentration of molybedate and chromate anions. The presence of these anions inhibits the pitting corrosion of steel samples in the order phosphate > molybedate > chromate. The effect of different inorganic anions on the corrosion behavior of two different composition steel samples was also studied in HCl solution.