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

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 CrO42-, WO42- or MoO42- 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.