Study on the Synthesis and Corrosion Inhibition Performance of Mannich-Modified Imidazoline

Abstract

A novel Mannich-modified imidazoline (MMI) as cationic emulsifier was synthesised for corrosion harm reduction, through three steps -acylation, cyclization, and Mannich reaction. The surface activity was characterized by determination of surface tensions and critical micelle concentration (CMC). The corrosion inhibition performance of five types of steels in the simulated corrosion solution in the presence of the MMI was investigated by static weight loss tests. The results showed that the MMI had good surface activities, with CMC of 19.8 μg g . The corrosion test results indicated that the corrosion rates of different materials were decreased significantly, and degrees of corrosion inhibition were always higher than 80.0 %. The main inhibition mechanism was most likely due to the adsorption of the corrosion inhibitor on the steel surface, leading to the prevention of corrosion medium from the metal surface. with a magnetic stirrer, temperature thermocouple, and backflow apparatus. Upon being heated under reflux at 150 °C, the whole reaction mixture was stirred for 3.5 h, and 6.8 cm 3 of the water produced in the reaction was collected, which indicated that the acylation reaction was 94 % complete. After xylene was distilled, the temperature of the reaction system was elevated to 240 °C, and the vacuum degree was kept at 0.096 MPa using vacuum pump for 4 h. The cyclization reaction occurred in the process. The reaction process was monitored by the on-line infrared test system (React IR ic10). This system is based on the principle of infrared (IR) spectroscopy, through the determination of characteristic absorption peak strength change in real-time monitoring of the reaction process. Keywords Mannich, emulsifier, imidazoline, CMC, corrosion inhibitionFinally, the Mannich reaction occurred with addition of methanal (0.4 mol) and acetone (0.4 mol) to the intermediate, and the final product 4-((2-((2-((2-(2-undecyl-4,5-dihydro-1H-imidazol-1-yl)ethyl)amino)ethyl)amino)ethyl) amino)butan-2-one coded as MMI was gained. The schematic of synthetic steps is shown in Fig. 1. IR and surface activity determination of the MMIThe infrared absorption spectrums of the intermediate and the final products were monitored by Thermo Nicolet NEXUS FT-IR spectrometer at 2 cm −1 resolution. The measurement of surface tension and the critical micelle concentration (CMC) at 25 °C were carried out by TX500C interfacial tension meter. The corrosion inhibition performance of the MMIThe corrosion inhibition performance of the MMI was investigated by static weight loss tests in the simulated corrosion solutions. The surface morphologies of specimens after immersion in HCl solution for 4 h, in the absence and presence of the MMI at different temperatures, were performed by SEM. The accelerating voltage was 20.0 kV. Results and Discussion Synthesis of the MMIThe synthetic installation is shown in Fig. 2. After the substrates were added into the reactor, the infrared-line testing system (React IR ic10) probe was put into the reaction sys...