Corrosion resistance of galvanized steel in concrete: effect of wetdry cycles in chloride solution after carbonation process

摘要

The effect of chloride ions on corrosion resistance of galvanized steel in carbonatedconcrete was investigated. Galvanized steel sheets were embedded in cubic concretespecimens manufactured with a 52.5 R Portland cement; after curing in atmospherefor 39 days, the concrete specimens were submitted to carbonation and thento wet-dry cycles both in a 3.5 % NaCl solution and in tap water. Results show thatconcrete carbonation destroys the passivating layer of calcium hydroxyzincate, withformation of less protective products. Wet-dry cycles in tap water after carbonationdo not increase appreciably corrosion rate of galvanized steel with respect to thatmeasured in not carbonated concrete. On the contrary, corrosion rate measurementsperformed during wet-dry cycles in 3.5 % NaCl solution, after concrete carbonation,indicate that in these conditions galvanized steel is not passive.