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

Abstract

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.

Rust layer growth and modification by a tannin-based mixture for lowering steel corrosion rates in neutral saline solution

“…This conclusion is in concordance with the previously published impedance data [19], for the similar system that showed that the inhibitor-modified rust layer has a low-frequency constant phase element n parameter close to 0.5, as well as the typical shape of Nyquist plots [35], which implicates diffusion effects in the porous surface layer.…”

“…Tannate species that have previously been proven by FTIR [19] and visible due to deep blue–black colour have not been detected due to their amorphous nature.…”

“…We have recently proposed the idea of rust layer conversion by a chestnut tannin-based mixture of environmentally acceptable compounds acting from the solution and producing a resilient inhibitor-modified rust layer that would lower corrosion rate to acceptable level and retain its protective properties for a substantial time period even after the inhibitor removal from the solution [19]. In the present study, we focus on the mechanism of inhibition of a simpler tannin-based mixture and quantitation of the synergistic and antagonistic effects between tannin, propolis [20][21][22] and benzoate [23] during the period of inhibitor-modified rust layer formation in the inhibitor-containing solution and during layer retention period in the inhibitor-free solution.…”

“…In the present study, we focus on the mechanism of inhibition of a simpler tannin-based mixture and quantitation of the synergistic and antagonistic effects between tannin, propolis [20][21][22] and benzoate [23] during the period of inhibitor-modified rust layer formation in the inhibitor-containing solution and during layer retention period in the inhibitor-free solution. In addition, we investigated the possibility of synergistically lowering our previously reported 2000 ppm tannin concentration [19]. For each compound and various compound mixtures, retention of the inhibitor-modified rust layer at the electrode surface is studied as a function of electrolyte velocity using a dynamic film persistency measurement based on linear polarisation resistance (LPR) technique [24] and potentiodynamic polarisation.…”

Recent developments in sustainable corrosion inhibitors: design, performance and industrial scale applications

“…Recently, inhibition effect of chitosan modified PEG was reported for mild steel in 1M HCl [145]. PEGs are also widely used as corrosion inhibitors in NaCl [452][453][454] and MOH (metal oxide) [455][456][457] solutions.…”