Evaluation of 4-(N-nitrosubstituted arylidene)-2-phenyloxazol-5(4H)-one derivatives as corrosion inhibitors for mild steel in Acidic Conditions

Abstract

Corrosion of industrial metals accounts for substantial economic losses globally, necessitating efficient and cost-effective inhibitors. Among various techniques to reduce corrosion, the use of corrosion inhibitors is one of the most promising solutions. The corrosion inhibition activity of organic inhibitors depends on the adsorption efficiency to the surface of the metal. The inhibitory effect of these inhibitors depends on their interactions with the mild steel surface via the adsorption process. Heteroatoms such as nitrogen and oxygen in azlactone structures serve as active centers for adsorption, making them highly effective corrosion inhibitors. In this study, 4-[(2-nitrophenyl)methylidene]-2-phenyl-1,3- oxazol-5-one (AZL-1), 4-[(3-nitrophenyl)methylidene]-2-phenyl-1,3-oxazol-5-one (AZL-2) and 4-[(4- nitrophenyl)methylidene]-2-phenyl-1,3-oxazol-5-one (AZL-3) were synthesized according to the Erlenmeyer reaction. The synthesized compounds were analyzed and confirmed by spectroscopic methods such as FT-IR, 1H-NMR, 13C-NMR and High-Resolution Mass Spectrometry. Then their inhibitory activities for the corrosion of mild steel (AISI 1018) were examined in 0.5 M hydrochloric acid medium. Weight loss, corrosion rate, inhibition efficiency and kinetic parameters of the synthesized compounds were studied for A1S1 1018 mild steel using weight loss method. Kinetic parameters were studied under 303, 313, 323 and 333 K temperature conditions. Kinetic studies have shown that, when increasing the temperature of the corroding medium the weight loss was increased, and mild steel was corroded fast. Also, when increasing the amount of inhibitor concentration in the corroding medium the mass loss of the mild steel specimens decreased significantly. Based on the results from the weight loss method after a 5-hour immersion period, AZL-1 demonstrated the highest corrosion resistance compared to AZL-2 and AZL-3, with corrosion inhibition efficiencies of 87.18%, 61.99%, and 52.90% respectively. Electrochemical impedance studies can be performed to investigate the mechanism behind the corrosion inhibition and to determine why the ortho nitro-substituted compound (AZL-1) exhibits greater inhibition efficiency compared to the para and meta nitro-substitute azlactones (AZL-2 and 3).