Preferential Site for Scaling on Carbon Steel with Corrosion Products

Although it has been pointed out that corrosion products are the preferred scaling site, the detail research has not been conducted. In this study, the initial scaling sites on carbon steel with corrosion product were investigated and scaling mechanisms were discussed. Carbon steel sheets were immersed in a solution supersaturated condition for magnesium silicate under normal standard state. Scaling at a corroded part on carbon steel was easier to occur than that at non-corroded part on carbon steel. The corrosion product was comprised of Fe2O3 (Hematite), Fe3O4 (Magnetite), and beta-FeOOH (Akaganeite). When the particles of Fe2O3, Fe3O4, and beta-FeOOH were individually i mmersed in the solution, the formation of magnesium silicate occurs only on beta-FeOOH. One of the preferred scaling sites for magnesium silicate was beta-FeOOH. The physical and chemical interactions were investigated. The physical interactions were evaluated by zeta potential, and the results suggested that the repulsion occurs between them. On the other hand, the chemical interaction was evaluated by IR and Raman analyses. Only IR spectrum of beta-FeOOH changed. The change was derived from absorption range of Fe-OH in beta-FeOOH. The OH group in beta-FeOOH may react with silanol group by the dehydration-condensation reaction.