Chloride-induced corrosion inhibition by binary mixtures in reinforced concrete structures

Corrosion inhibitors are used to prevent or delay corrosion in reinforced concrete structures. Available commercial products are based on nitrite or organic mixtures based on amines, alkanolamines, fatty acids and carboxylic substances. During the last 15 years, an intense experimental research has been carried out focused at identifying new organic substances or binary mixtures that might have inhibiting effectiveness on chloride-induced corrosion. The paper describes results of potentiodynamic and potentiostatic electrochemical tests carried out in alkaline solution, in the presence of chlorides, on binary mixtures with nitrite, dimethylethanolamine (DMEA), glutamine and benzoate. Some of the mixtures exhibited a marked synergistic effect in the potentiodynamic polarisation tests, with a clear increase in pitting potential. A certain effect on chloride threshold was also observed in potentiostatic polarisation. The best mixtures are able to increase the critical chloride content, then accordingly they can delay corrosion initiation on real reinforced concrete structures.