Abstract
Two isoxazolidine derivatives namely 5-(benzo[d][1,3]dioxol-5-ylmethyl)-2-tetradecyl isoxazolidine (BDMTI) and 5-(4-hydroxy-3-methoxybenzyl)-2-tetradecyl isoxazolidine (HMBTI) were synthesized and characterized using FTIR, C-NMR, H-NMR, and elemental analysis. The synthesized compounds were evaluated as corrosion inhibitors for API 5L X60 steel in 1 M HCl in the temperature range of 25–60 °C using gravimetric and electrochemical (Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP) and Linear Polarization Resistance (LPR)) techniques. The effect of addition of a small amount of iodide ions on the corrosion inhibition performance of the compounds was also assessed. In addition, quantum chemical calculations and Monte Carlo simulations were employed to correlate the electronic properties of the compounds with the corrosion inhibition effect as well as to evaluate the adsorption/binding of the inhibitor molecules on the steel surface. Experimental results show that the two compounds inhibited the corrosion of carbon steel in an acid environment with HMBTI showing superior performance. The corrosion inhibition effect was found to be dependent on the inhibitors' concentration and temperature. Addition of iodide ions improves the inhibition efficiency considerably due to co-adsorption of the iodide ions and the inhibitors on the steel surface which was competitive in nature as confirmed from the synergistic parameter (S1) which was less than unity at higher temperature. Experimental and theoretical results are in good agreement.
Highlights
The effective strategy adopted by the oil, gas and chemical industries in order to maximize pro t and reduce cost is to use low carbon steel in place of expensive corrosion resistant alloys (CRAs) in their operations
It is clear from the gures that corrosion rate decreased in the presence of the inhibitors compared to the blank solution. This is a clear indication that both BDMTI (7) and HMBTI (8) retard the dissolution of steel sample in the acid environment
The corrosion inhibition effect of the synthesized compounds for API 5L X60 steel in 1 M HCl solution was evaluated using weight loss and electrochemical techniques complemented with surface analysis of the corroded steel samples immersed in uninhibited and inhibited solutions with scanning electron microscope (SEM)
Summary
The effective strategy adopted by the oil, gas and chemical industries in order to maximize pro t and reduce cost is to use low carbon steel in place of expensive corrosion resistant alloys (CRAs) in their operations. The major problem associated with low carbon steel is its susceptibility to corrosion when it comes in contact with corrosive environments such as acids (HCl, H2SO4, and H3PO4), chloride rich solutions and aqueous hydrogen sul de medium. Corrosion mitigation strategies adopted by some industries include materials selection, coatings and linings, cathodic protection and the use of corrosion inhibitors amongst others. The use of corrosion inhibitors is the most practical and cost effective method in ghting corrosion. Corrosion inhibitors retard corrosion by adsorbing onto the low carbon steel surface and blocking one or more of the electrochemical reactions occurring at the solution/metal interface.
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