Electrochemical studies on pitting corrosion of tin in sodium borate solutions containing nitrate ions

Abstract

Purpose – The purpose of this paper is to study the electrochemical behavior of Sn electrode in Na2B2O7 solutions in the absence and presence of NaNO3 as a pitting corrosion agent. Design/methodology/approach – The electrochemical behavior of Sn electrode was studied by using cyclic voltammetry and potentiodynamic polarization measurements and complemented with scanning electron microscopy examinations. Findings – This paper shows that in the absence of NO3 ions, the anodic polarization of Sn electrode exhibits active/passive transition. Addition of various concentrations of NO3 anions to the borate solution enhances active anodic dissolution and tends to break down the passive oxide film at a certain pitting potential. The pitting potential, and hence the pitting corrosion resistance, decreases with increasing NO3-ion concentration and temperature but increases with scan rate and repetitive cycling. Addition of CrO4 2 , WO4 2 or MoO4 2 oxyanions to the borate nitrate solution inhibits the pitting corrosion of Sn. Originality/value – This is the first study that shows the effect of NO3 ion as a pitting corrosion agent