Synthesis, crystal structure and anticorrosion performance of Zn(II) and Ni(II) complexes

Abstract Two unreported complexes [Zn(6-Me-2,3-pydc)(H2O)2•2H2O]n (namely complex 1, and 6-Me-2,3-pydc = 6-picoline-2,3-dicarboxylic acid) and [Ni(5-Br-2,3-pydc)(1,10-phen)2•9H2O]n (namely complex 2, and 5-Br-2,3-pydc = 5-bromopyridine-2,3-dicarboxylic acid, 1,10-phen = 1,10-phenanthroline) were synthesized by solvothermal method and were characterized and confirmed by elemental analysis, Fourier infrared spectroscopy, X-ray single crystal diffraction, thermogravimetric analysis and scanning electron microscope (SEM). The weight loss measurement (WL) results showed that complex 1 and 2 can maintain the inhibition efficiency above 86% at 85°C. The thermogravimetric analysis showed that two complexes have the excellent heating stability. Electrochemical studies results showed that complex 1 and 2 were cathode type corrosion inhibitors and exhibited maximum inhibition efficiency (ηp%) of 87.56% and 89.59% at the concentration of 1.50 mmol•L−1 in 0.5 N HCl, respectively. The adsorption isotherm analysis confirmed that complex 1 and 2 followed the Langmuir isotherm. SEM results confirmed that two complexes can effectively protect carbon steel from acid medium corrosion, which was consistent with the electrochemical studies results.