Abstract
Chromate free corrosion inhibitors are searched for to mitigate the economic loss caused by mid-steel corrosion. Here, we show metal-free organic inhibitors having free coumarate anions that can be used either as direct corrosion inhibitors or incorporated into a polymer coating obtained by UV-curing. Four different ionic liquid monomers and polymer coatings with hexoxycoumarate anion and different polymerizable counter cations were investigated. Potentiodynamic polarization, electrochemical impedance spectroscopy, and surface analyses have verified their corrosion inhibition performance on a mild steel AS1020 surface. In the case of the coumarate ionic liquid monomers, the most promising inhibitor is the one coupled with the ammonium cation, showing an inhibition efficiency of 99.1% in solution followed by the imidazolium, pyridinium, and anilinium. Next, the ionic liquid monomers were covalently integrated into an acrylic polymer coating by UV-photopolymerization. In this case, the barrier effect of the polymer coating is combined with the corrosion inhibitor effect of the pendant coumarate anion. Here, the best polymer coatings are those containing 20% imidazolium and pyridinium cations, presenting a greater impedance in the EIS (Electrochemical Impedance Spectroscopy) measurements and less evidence of corrosion in the scribe tests. This article shows that the cationic moiety of coumarate based ionic liquids and poly(ionic liquid)s has a significant effect on their excellent corrosion inhibition properties for a mild steel surface exposed to aqueous chloride solutions.
Highlights
Materials deterioration by corrosion is one of the biggest technological issues nowadays causing significant economic losses [1]
Scientists have been researching corrosion inhibitors which adsorb onto a metal surface and decrease the effects of corrosion processes by suppressing the anodic and/or cathodic electrochemical reactions
The protic ionic liquid monomers were obtainedwere by acid-base obtained by acid-base proton exchange reaction between commercially available monomers and proton exchange reaction between commercially available monomers and p-hexoxy coumaric acidp-as hexoxy coumaric acid as described in Scheme 2section
Summary
Materials deterioration by corrosion is one of the biggest technological issues nowadays causing significant economic losses [1]. The most used inhibitor is that based on well-known hexavalent chromium compounds that creates a complex oxide layer on the steel surface to act as a barrier to corrosion [3]. Over the years many different organic and organometallic compounds have been investigated as corrosion inhibitors [6,7]. The mechanism of action of organic corrosion inhibitors is based on the adsorption onto the surface to form a protective film which displaces water from the metal and protects it against deterioration due to attack by aggressive species such as chloride ions.
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