Electrode Potential Evaluation of Effect of Inhibitors on the Electrochemical Corrosion Behaviour of Mild Steel Reinforcement in Concrete in H2SO4

The electrochemical corrosion behaviour of mild steel embedded in concrete, and partially immersed in 0.2M H2SO4, was studied in this investigation at ambient temperature by potential monitoring technique. The experimental work was performed with a digital multimeter and a Cu/CuSO4 electrode (CSE) as the reference electrode. Extracts of carica papaya leaves and sodium nitrite (NaNO2) in different concentrations were separately and in combination, used as inhibitors. This paper reports the observed electrochemical response from the electrode potential monitoring of the embedded steel rebar during the experiments. The results obtained, showed a reduction in the active corrosion reactions behaviour of the embedded mild steel in concrete with added different concentrations of sodium nitrite and the pawpaw leaves extracts in the acidic test environment. This reduced active corrosion reaction was an indication of corrosion inhibition / protection characteristic. The observed inhibition was associated with the protective film provided on the embedded steel’s surface in the concrete by the complex chemical compounds of the plant leaves’ extracts and of the sodium nitrite with the alkaline composition/environment of the concrete constituents. The protective film prevented and/or reduced the chloride ions penetration to the steel surface. The combination of c. papaya extracts and the NaNO2 solution also provided effective corrosion inhibition of the embedded steel by synergism. The 100% concentration of each of the inhibitors and when in combinations, exhibited the most effective corrosion inhibition performance in the sulphuric acid test environment.