Preferential Site for Scaling on Carbon Steel with Corrosion Products

Abstract

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 β-FeOOH (Akaganeite). When the particles of Fe₂O₃, Fe₃O₄, and β-FeOOH were individually immersed in the solution, the formation of magnesium silicate occurs only on β-FeOOH. One of the preferred scaling sites for magnesium silicate was β-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 β-FeOOH changed. The change was derived from absorption range of Fe–OH in β-FeOOH. The OH group in β-FeOOH may react with silanol group by the dehydration-condensation reaction.