Vitamins: Potential inhibitors for nickel in acidic media

Abstract

Corrosion of Ni in 1N HNO₃ has been investigated in the presence of Vitamins B₁, B₆ and C. Galvanostatic study carried out at a temperature range of 308 K to 328 K revealed a very high inhibition efficiency of these additives. The I% varied in the range of 99·1–99·7% for 10⁻²M concentration of Vitamin B₁, 43·7–99·2% for 10⁻²M concentration of Vitamin C and 88–96% for 10⁻²M concentration of Vitamin B₆. The b_a and b_c slopes indicate that at higher concentrations, these additives act purely by the adsorption on the active sites, therefore inhibiting the corrosion processes. Adsorption of these inhibitors depends on the already adsorbed anions. A study of E_corr reveals that Vitamin C is a mixed inhibitor, inhibiting both cathodic and anodic processes to an equal extent whereas Vitamin B₁ and B₆ are predominantly cathodic inhibitors at 10⁻²M concentration. Passivation parameters suggest that these are non-passivating type of inhibitors. These results are supplemented by some surface analytical studies like SEM. The study at higher temperatures indicates that these are better inhibitors at higher temperatures as I% improves with the increase in temperature.