Localized Dissolution Kinetics of Low Carbon Steel

Aljana Petek* and Valter Doleček
Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova 17, 2000 Maribor
Tel.: +386 2 22 94 443; fax: +386 2 25 27 774
E-mail address: aljana.petek@uni-mb.si

Localized dissolution of low carbon steel in saturated calcium hydroxide with different amount of sodium chloride has been investigated, using a dc technique. Potentiokinetic polarization curves indicated that pitting potentials (Epit) decrease linearly with the log of chloride concentration. The rate of pit nucleation (1/ti), and the rate of pits growth increases with increasing concentration of Cl- ions. Initiation of pitting attack could be ascribed to the adsorption of Cl- ions on the oxide surface. Adsorption of Cl- ions is physisorption and follow the Langmuir isotherm with ∆adsG0 = –21.1 kJ/mol.

Keywords: Pitting corrosion; adsorption isotherm; low carbon steel; simulated interstitial solution.