IN-SITU RADIOTRACER STUDIES OF SORPTION PROCESSES IN SOLUTIONS CONTAINING (BI)SULFITE IONS .2. LOW-CARBON STEEL

In this paper, time, potential and pH dependence of SO42- and HSO3- ac cumulations measured by an in-situ radiotracer method on surface oxide layers of low carbon steel are presented and discussed. This work is a continuation of a research program[ld] and deals with the characteri zation of the sorption behaviour of low carbon steel in solutions cont aining sulfate and bisulfite ions (as a possible model of acid rain). From the experimental results it can be stated that (i) the presence o f bisulfite ions in the solution phase accelerates the corrosion of lo w carbon steel; (ii) at E > 0.40 V the electrooxidation of HSO3- ions presumably proceeds to yield a steel surface covered with oxidation pr oducts leg sulfate, dithionate[1]); (iii) surface excess values of SO4 2- and HSO3- ions (as well as the oxidized and reduced adspecies of bi sulfite) are very high (up to Gamma = 6 x 10(-8) and Gamma = 1 x 10(-8 ) mol cm(-2), respectively) ie, a significant incorporation of aggress ive ions into the surface oxide layers occurs; (iv) the strong embeddi ng of anions studied is probably the result of some selective chemical interactions (chemisorption) of the above species with active sites i nvolved in the steel surface undergoing structural transformation. Cop yright (C) 1997 Elsevier Science Ltd.