Corrosion Products of Galvanized Rebars Embedded in Chloride-Contaminated Concrete

Iron corrosion products of steel reinforcement result in staining, cracking, and spalling of concrete structures. These effects of corrosion require costly repairs and maintenance during the useful life of the structures. To prevent corrosion of important infrastructure projects, galvanized reinforcing steel occasionally is used. The performance of galvanized steel in chloride-contaminated concrete is attributed to the corrosion product form: zinc oxide (ZnO), which is less voluminous than iron corrosion products. However, zinc corrosion products detected on galvanized reinforcement are rather controversial. Some authors identified another compound: zinc hydroxychloride (Zn₅[OH]₈Cl₂·H₂O). This product occupies more space than ZnO and can induce cracking of the cover concrete. Other authors found zinc hydroxychloride and zinc hydroxide (Zn[OH]₂). In this work, ZnO and Zn₅(OH)₈Cl₂·H₂O were identified. Under some conditions (exposure time in aggressive environment and coating thickness) and after cracking of concrete cover, Zn(OH)₂ also was found.