Effectiveness of corrosion inhibitors in saturated calcium hydroxide solutions acidified by acid rain components

Aggressive air pollutants are known to attack concrete and threaten its integrity and decreasing the pH value. The compounds produced by the reaction of concrete hydration products with these aggressive agents cause the pH of concrete matrices to decrease, depassivating the surface of reinforcing steel and leading to the corrosion process. The effect of sodium nitrite and sodium molybdate as corrosion inhibitors was therefore analyzed in a saturated calcium hydroxide solution polluted with sulfuric and nitric acids (acid atmosphere). Both compounds exhibited significantly inhibitory effects, depending on the concentration. At low concentrations (0.013% total solution mass), sodium molybdate proved more efficient than sodium nitrite, but their inhibitory effect was found to be similar at high concentrations (0.040% total solution mass). (C) 2007 Elsevier Ltd. All rights reserved.