A Novel Environmentally Friendly Synergistic Mixture for Steel Corrosion Inhibition in 0.51 M NaCl

The ubiquitous use of plain and low-alloy steels in neutral, chloride bearing environments presents an everyday challenge for corrosion protection professionals. This paper explores the possibility of developing a non-toxic and environmentally friendly synergistic inhibitor mixture made of propolis, tannin, sodium benzoate, PEG400 and starch that could be applied into the solution to induce the formation of a persistent protective layer on steel. Components of the mixture were chosen based on the references giving their characteristics relevant to their possible action in the solution and/or at the surface of the steel. The efficiency of the protective layer formed under the influence of the inhibitor mixture, and then measured by the LPR probe in the inhibitor-free solution, was the lowest under quiescent conditions (75%) and the highest (95%) under flow conditions. Both, LPR and EIS data indicate that the inhibitor modified layer presents a barrier for diffusion of oxygen that acts as a primary corrosion reaction depolarizer in the investigated neutral chloride solution. The demonstrated persistence of the inhibitor modified layer is of primary interest as it gives possibility batch application.