Efficiency of traditional and innovative protection methods against corrosion

The corrosion resistance of cracked concrete specimens reinforced with bare, stainless, or galvanized steel plates are compared with the corrosion behavior of bare steel reinforcement embedded in concrete specimens coated with a flexible polymer-cement based mortar either before or after specimen cracking and with those related to bare and galvanized reinforcement embedded in hydrophobic concrete. The specimens were exposed to increasingly aggressive environments: forty days of full immersion in a 3.5% sodium chloride aqueous solution were followed by five months of wet-dry cycles using a 10% sodium chloride aqueous solution. The results for the full immersion condition show that negligible corrosion rates were detected in all the cracked specimens, except those treated with the flexible polymer-cement mortar before specimen cracking and the hydrophobic concrete specimens especially when bare steel reinforcement are adopted. On the other hand, high corrosion rates were measured in all cracked specimen exposed to wet-dry cycles, except for those with stainless steel reinforcement and those coated with the flexible polymer-cement mortar after specimen cracking, as was expected, and, surprisingly, for the galvanized steel reinforcement embedded in hydrophobic concrete.