Experimental and Theoretical Studies of Tailor-made Schiff Bases as Corrosion Inhibitors for Carbon Steel in HCl

Abstract

Strong acids used in industrial applications as cleaning, descaling, among others, can severely damage metallic structures, requiring corrosion inhibitors to diminish or avoid these issues. Since many conventional compounds used for this purpose may result in environmental and human health issues, eco-friendly compounds such as Schiff bases have been recently investigated. The synthesis of three novel Schiff bases (SBs) was confirmed by infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonance (1 H-NMR). Weight loss measurements were carried out in 1 M HCl over 303K-333K. Furthermore, the combination of these compounds with a surfactant improved the efficiencies, reaching an efficiency of 93%. Optical and scanning electron microscopies confirmed the reduced roughness and pit depths of carbon steel samples. Density-functional theory calculations for neutral forms of SBs revealed that the geometrical and the energetical parameters are similar for the three studied SBs. The geometrical results exhibited more planar structures of protonated species, improving the chemical and physical interactions between aromatic rings and metallic atoms.