Prediction of Pitting Corrosion in Tinplate from Capacitance Measurements

Abstract

A method for predicting the occurrence of one type of pitting corrosion in plain tinplate cans of food is described. The method involves measuring the double layer capacitance of a tin electrode over the potential range —0·60 V to —1·65 V relative to the saturated calomel electrode (S.C.E.). Adsorption of organic materials on the tinplate surface, which leads to pitting corrosion, may be detected from the shape of the capacitance – potential curves. The shape of the curves correlated with the type of corrosion caused by several acid foods, some of which caused pitting while others caused detinning. Adsorption of chemical additives on the tin electrode surface appeared to depend on the ‘chemical softness’ of the materials.