Efficacy of an organic–inorganic hybrid phosphorus compound in corrosion mitigation of reinforcement steel in concrete. I. Gravimetric and electrochemical analysis

Bis(hexamethylene)triamine-pentakis(methylphosphonic acid) (BTPMP) was investigated for its inhibiting action on corrosion of Fe500D reinforcement steel. Results of gravimetric studies inferred that 10 mM of BTPMP is effective in corrosion control of the steel in saturated calcium hydroxide solution tainted by chloride ions. According to the electrochemical studies, the interface of the metal/solution exhibits higher charger transfer resistance and lower constant phase element values in the presence of BTPMP. The open circuit potential (OCP) measurements indicate that the presence of BTPMP shifts OCP values of steel in concrete in positive direction. The nature of the film is protective as observed from prolonged time taken for failure of BTPMP-protected rebar compared with unprotected rebar during accelerated corrosion tests. Furthermore, it is observed that the bond strength between concrete and steel is unaffected by the inhibitor film.