Role of additives on the corrosion behaviour of nickel in 5% sulphuric acid

Abstract

Effect of various additives on the corrosion behaviour of nickel in sulphuric acid has been studied using potential measurement and potentiostatic methods. The potential of nickel was measured with respect to time as well as at different concentrations of Hg2+, Cu2+, NO3-and picric acid. Attempts have been made to analyse the electrolytic adsorption characteristics of above ionic species through measurement of C/êE vs C (where, C is concentration of cation or anion under study and êE is the change of potential). A monolayer Langmuir adsorption isotherm was observed to form in most of the cases. Potentiostatic polarization curves indicated that mercury and copper ions inhibited the corrosion of nickel in sulphuric acid. The addition of Hg (II) and Cu (II), shifted the passivation potential in the noble direction and critical current density was many fold lower than the critical current density in absence of additives.