MIGRATING ORGANIC CORROSION INHIBITORS FOR PROTECTION OF STEEL REINFORCEMENT

Steel reinforcement of concrete structures is normally passivated due to high pH value of concrete interstitial electrolyte (pH 13-14). However, chloride contamination (e.g. deicing application, marine environment) can initiate a local breakdown of passive layer and corrosion of rebar. One of the most effective methods to stop or reduce the chloride-induced corrosion of rebar is the use of corrosion inhibitors. As corrosion inhibitors are widely used inorganic nitrites as preventive corrosion inhibitors or organic compounds of different composition (e.g. based on amines and alkanolamines) as curative corrosion inhibitors. The paper is focused on applicability of commercial products based on dimethyldidecyl ammonium (bi)carbonate and polyethyleneimine as corrosion inhibitors for the steel reinforcement. One of the advantages of these inhibitors is their cationic nature, which enables to remove chloride anions by electrochemical extraction simultaneously with electrochemical injection of inhibitor. Their inhibition efficiency was evaluated by means of polarization resistance of non-corroded and pre-corroded steel samples at different time intervals (15 min, 1 h and 24 h after addition of an inhibitor). The inhibition efficiency of 0.2 % solutions were compared with that of sodium nitrite. The results showed some inhibition capability of all studied compounds but only with nitrite on non-corroded steel were achieved values corresponding to an acceptable corrosion rate of steel reinforcement in concrete structures.