Innovative metal-free coumarate based ionic liquids and acrylic UV-coatings as corrosion inhibitors

Abstract

The thesis is focused mainly on anticorrosive ionic liquids and polymer coatings. Various metal - freeorganic inhibitors based on aromatic carboxylates, p-coumaric acid, and the preparation polymeranticorrosive coatings for mild steel surfaces were developed. Corrosion inhibition was tested byelectrochemical impedance spectroscopy and surface analysis. The thesis is divided in three projectswhich studies the corrosion inhibition performance of various coumarate derivatives based inhibitors andpolymer coatings.First, metal - free organic ionic liquids that can be used as direct corrosion inhibitors or incorporated intoa polymer coating were developed. p-coumarate anion based UV curable organic monomers and polymercoatings were synthesized. All compounds reduced mainly the anodic corrosion reaction creating aninhibitor passive film.Second, corrosion inhibitors in the form of ionic liquid monomers and polymer coatings were synthesizedand the effect of different counter-cations were investigated. It was demonstrated that the cationic moietyof coumarate based ionic liquids and poly(ionic liquid)s is affecting their excellent corrosion inhibitionproperties onto the mild steel surface.Third, the effect of including the coumarate corrosion inhibitors by three different ways into the acrylicUV coating was investigated. Inhibitors were added simply as an additive, ionically attached orcovalently attached to the acrylic polymer coating. Thus, two different Ionic liquid methacrylicmonomers and one non-polymerizable ionic coumarate compound were synthesized. All inhibitors wereintegrated in a typical polymer coating formulation and the monomer mixture were photopolymerized. Itwas demonstrated that the UV polymer coating which shows the best anti-corrosion performance is theone where the coumarate group is attached covalently to the methacrylate group followed closely by theone where is attached ionically. The UV-coating where the non-polymerizable coumarate compound isadded as an additive without any link or strong interaction presents leaching problems limiting itsanticorrosion effect.