Corrosion of tin in citric acid solution and the effect of some inorganic anions

摘要

The corrosion behaviour of tin in different concentrations of citric acid solutions (0.3-1.0 M, pH = 1.8) was studied at 30 degreesC by potentiodynamic technique. The E/I profiles exhibit an active passive behaviour. The active dissolution involves one anodic peak A associated with a dissolution of the metals as Sn(II) species. The passivity is due to the formation of thin film of SnO2 and or Sn(OH)(4) on the anode surface. The cathodic sweep shows a small peak C related to the reduction of the passive film. The peak current density I-p of peak A increases with increasing both acid concentration and sweep rate. The effects of adding increasing concentrations of Na2CrO4, NaMoO4, NaNO3 and NaNO2 on the corrosion of tin in 0.5 M citric acid at 30degreesC were investigated. Both CrO42- and MoO42- ions inhibit the corrosion of tin and the extent of inhibition enhances with their concentrations. Addition of either NO3- or NO2- accelerates the corrosion of tin. NO3- ions are more aggressive than NO2- ions. (C) 2003 Elsevier Science B.V. All rights reserved. [References: 19]