Validation of corrosion rates measured by the Tafel extrapolation method

This paper discusses the validity and limitations of the Tafel extrapolation method for the determination of corrosion rates for activation-controlled corrosion processes. Experimental corrosion rates determined by the Tafel method are compared with corrosion rates obtained by an independent chemical (i.e., non-electrochemical) method for iron in hydrochloric acid, iron in 3.5% NaCl, and for titanium in boiling 1 M sulfuric acid. The methods of confirmation of the corrosion rates involved colorimetric analysis of the dissolved cation or the use of an ion-implanted inert Xe marker. Additional examples taken from the literature involving other metals and other methods of validation are also discussed.