RED MUD AS A CORROSION INHIBITOR FOR REINFORCED CONC

The effectiveness of red mud as corrosion inhibitor of carbon steel embedded in concrete was evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. The testing media were red mud solutions (pH=12), alkaline solutions having the same pH (NaOH 0.08M and Ca(OH)2 0.04M), and reinforced mortar. In all cases chloride additions were used for evaluating the inhibition effectiveness. The results show that red muds are able to maintain steel passivity in presence of high chloride concentration, i.e., in mortar 3% CaCl2 by weight of cement, and in solution a ratio Cl-/OH- equal to 5 (maximum tested values).