Water-based corrosion inhibitor for prevention and repair of reinforcement in chloride and carbonated environment

Abstract

This paper explores the influence of 2-aminopyridine (2AP) as water-based migratory corrosion inhibitor (M-CoI) on the corrosion resistance of reinforcing steel bars embedded in ordinary Portland cement and pozzolanic Portland cement concrete subjected to combined chloride and carbonation ingress. Two applications of 2AP are considered i.e., preventive (applied before exposure to aggressive environment) and repair (applied after corrosion initiates). Corrosion performance was assessed using electrochemical techniques and gravimetric mass loss method. The study also examines the impact of 2AP application on chloride ion concentration and carbonation depth of both concrete systems. The compressive strength of each concrete system was also measured to study the impact of M-CoI application on strength properties. Surface condition of hardened concrete and extracted rebar was evaluated by optical microscopy. Results conclude that 2AP effectively retards reinforcement corrosion when used as preventive measure by forming a homogeneous inhibitive layer on steel. However, when used as a repair technique, localised and uniform corrosion was perceived. An attempt has been made to identify the cause of non-performance of 2AP as repair measure. It was concluded that reached concentration of 1 mM was not sufficient to reduce ongoing corrosion due to the accumulation of corrosion products. The influence of the inhibitor on chloride profile and carbonation depth was found to be insignificant. It is concluded that chloride ions initiate the corrosion mechanism, while carbonation exacerbates it, particularly in blended cement concrete. Nonetheless, inhibitor application can provide similar resistance in both concrete systems.