Properties And Synthesis Of Benzimidazole-Based Phosphate-Free Polyether Copper Corrosion Inhibitor

Copper and its alloys have been widely used in various fields such as electronics,solar cells,structural materials,handicrafts,currency and thermal cycling systems in industrial production because of their good thermal conductivity,mechanical processing,corrosion resistance and other properties.Copper and its alloys are very stable under normal conditions,but in some conditions,especially with the presence of Cl~-,copper and its alloys can cause severe corrosion and shorten their service life.Adding corrosion inhibitors is the most effective and common metal corrosion protection in industrial applications.At present,effective copper corrosion inhibitors in NaCl solution are generally the substances such as imidazole,benzotriazole,thiadiazole,and their derivatives which including atoms such as N,P and S.Unfortunately,these compounds generally have biological toxicity that can endanger the health and pollute the environment.Therefore,there is an urgent need to develop a new type of green corrosion inhibitor that is highly efficient and harmless.As a common pickling inhibitor,benzimidazole compounds have the advantages of high efficiency,low toxicity and easy degradation and so on.Based on the past work in the laboratory,the polyether monomers MPEB and MPEB are generated by the carboxylation of polyethylene glycol monomethyl ether by using anhydrous oxalic acid and tert-butyl bromoacetat.And then to produce benzimidazolyl phosphorus-free polyether copper corrosion inhibitors OPD/MPEM and OPD/MPEB by using cyclization with carboxylic acid and o-phenylenediamine under acidic conditions.The structures were characterized by infrared spectroscopy(FT-IR)and nuclear magnetic resonance(~1H-NMR).The corrosion inhibition performance and mechanism of synthetic benzimidazolyl phosphorus-free polyether copper corrosion inhibitors OPD/MPEM and OPD/MPEB in 3.5 wt.%NaCl solution at 45?,were evaluated by dynamic weight loss,electrochemical techniques(Tafel and EIS),scanning electron microscopy(SEM)measures,energy dispersive spectrometer(EDS)analysis and molecular adsorption thermodynamics.The results showed that the corrosion inhibition efficiency increased first and then gentle and slightly lower with the increasing concentration of OPD/MPEM and OPD/MPEB in 3.5 wt.%NaCl solution at 45?.OPD/MPEM reached the maximum inhibition rate at the level of60 mg/L.OPD/MPEB reached the maximum inhibition rate at the level of70 mg/L.Moreover,both OPD/MPEM and OPD/MPEB are mixed inhibitor copper corrosion inhibitors that form an adsorption film on the copper surface to reduce copper corrosion effectively and the adsorption type obeys Langmuir single layer adsorption.At the same time,the corrosion mechanism of corrosion inhibitor are discussed in this paper by using quantum chemical calculation and molecular dynamics simulation.The results showed that both OPD/MPEM and OPD/MPEB have high reactivity and they form a layer of protective film to play a role of corrosion effectively by giving their own electronic form chemical bonds to the empty d orbitals of copper surface.