The effects of structural variation in some isoxazolidines on the corrosion inhibition of carbon steel in 0.5 M sulfuric acid

Purpose - The aim is to demonstrate corrosion inhibition capabilities of several isoxazolidines, containing hydrophobic substituents and having varying degree of steric congestion around nitrogen. Design/methodology/approach - A number of isoxazolidines were prepared. Corrosion inhibition efficiencies of these organic compounds were determined by gravimetric and electrochemical methods, using carbon steel as the substrate metal and 0.5 M H ₂SO₄ at 40-70°C as the corrosive environment. Concentration of inhibitor was varied between 5 and 400 ppm. Findings - Increase in steric congestion around the nitrogen centre and hydrophobic chain lengths as well as increase in temperature (in the presence of the inhibitor in the higher concentration range 100-400 ppm) were found to increase the corrosion inhibition efficiency of the isoxazolidines. Electrochemical measurements corroborated these results. Thermodynamic parameters (ΔG _ads⁰,ΔH_ads⁰,ΔS _ads⁰) for the adsorption process and kinetic parameters for the metal dissolution (or hydrogen evolution) reaction were determined. Originality/value - This is the first time the corrosion inhibition characteristics of isoxazolidines, an important class of readily accessible compounds, have been evaluated in H₂SO₄ medium.