A quinoline-based quaternary ammonium salt dimer as corrosion inhibitor for N80 steel in lactic acid solution

In an effort to develop an effective corrosion inhibitor which is applicable to the chelating acidizing fluids in petroleum production, a novel heterocyclic quaternary ammonium salt dimer (TQD) was synthesized through the reaction of quinoline with 4-chloromethylthiazole hydrochloride. An analogue compound, benzyl quinolinium chloride dimer (BQD), was also prepared for comparison. Their anti-corrosion performances in 15% lactic acid solution were investigated through weight-loss experiments, electrochemical tests, surface morphology observation and simulation calculations. The outcomes demonstrate that inhibition efficiency of 99.38% has been achieved with 0.1% TQD at 363 K, which is much higher than that of BQD at the same condition. Both inhibitors were consistent with the Langmuir model, and both were hybrid adsorption, including physical and chemical adsorptions. According to the results of surface analysis (SEM, AFM, XPS, contact angle) and theoretical calculation (DFT and MD), TQD can effectively slow down the metal corrosion in lactic acid and thus is a promising inhibitor for oil and gas well acidizing purpose. The stronger adsorption capacity of TQD may come out of the contribution of thiazole rings in the molecules.