Influence of the conversion coating on the corrosion of galvanized reinforcing steel

Galvanized reinforcing steel with a cerium conversion coating have been studied in Ca(OH)2 saturated solution with and without chlorides. Electrochemical results reveal that cerium conversion coating provides an effective corrosion resistance compared to galvanized steel at short immersion times, 5 days without Cl ions and 2 days with Cl in the solution. The results suggest that cerium layer inhibits hydrogen evolution on the galvanized coating at early stages. At longer immersion times, galvanized steel with cerium conversion coating and galvanized steel describe similar corrosion behaviour in both electrolytes. There is not significant differences in the corrosion current density, about 5 μA/cm2, due to the presence of chlorides ions in the Ca(OH)2 saturated solution up to approximately 17 days of immersion. At longer immersion times, from 30 to 50 days, specimens in the chlorides containing solution exhibit higher corrosion activity than that recorded in the free Cl solution revealing that cerium layer cannot inhibit the localized attack promoted by chloride ions.