Improved corrosion resistance of mild steel in acidic solution by hydrazone derivatives: An experimental and computational study

Poor corrosion resistance of mild steel (MS) is a serious concern in many industrial applications. Application of corrosion inhibitors is a possible solution to combat steel corrosion. As yet, there is very little research reported focusing on hydrazone derivatives as corrosion inhibitors, here we present a combined experimental and theoretical study of the adsorption of three newly synthesized hydrazones (HDZs), namely, (E)-N′-(4-(dimethylamino)benzylidene)-2-((2,3-dimethylphenyl)amino)benzohydrazide (HDZ-1), (E)-2-((2,3-dimethylphenyl)amino)-N′-(4-methylbenzylidene)benzohydrazide, (HDZ-2) and (E)-N′-benzylidene-2-((2,3-dimethylphenyl)amino)benzohydrazide (HDZ-3) on the MS surface in 1 M HCl. The interaction of HDZs and the metal surface was investigated using electrochemical techniques, X-ray photoelectron spectroscopy (XPS), DFT and molecular dynamic (MD) simulations. XPS shows that inhibitor molecules form a stable layer on steel surface through chemical and physical interactions. HDZs adsorption onto the steel surface was found to follow Langmuir model. Furthermore, electrochemical measurement results demonstrated that our developed inhibitors act as of mixed-type (anodic and cathodic), with HDZ-1 showing the highest polarization resistance and lowest corrosion current density. Scanning electron microscope (SEM) was used to examine the surface morphology of the steel samples. The new hydrazones showed significantly improved steel corrosion resistance, which provides opportunities to explore the inhibitive activity of structurally similar compounds.