Corrosion inhibition of triethanolammonium bromide mono‐ and dibenzoate as cationic inhibitors in an acidic medium

Abstract

A weight loss technique was used to determine the corrosion inhibition efficiency of synthesized alkyl monoand dibenzoate triethanolammonium bromide derivatives (TEAMB, TEADB) in an acidic medium (2 N HCl) at different doses (50, 100, and 200 ppm). The results showed that monoderivatives had a higher corrosion inhibition efficiency than diderivatives. The results were correlated with several factors, including the alkyl chain length of the hydrophobic chains, interfacial tension (IT), critical micelle concentration (CMC), and adsorption free energy of these inhibitors. Increasing the geometric length of the alkyl chains in the synthesized inhibitors had an increasing effect on their corrosion inhibition efficiency, whereas decreasing the CMC and IT had an increasing effect on their tendency toward corrosion inhibition. The number of hydrophobic chains attached to the inhibitor molecules had a vital influence on their efficiency as corrosion inhibitors.Paper no. S1491 in JSD 8, 283-287 (July 2005).KEY WORDS: Adsorption free energy (∆G ads ), amphipathic structure, chemisorption bond, corrosion inhibition efficiency, critical micelle concentration (CMC), geometric length, geometric structure, interfacial tension (IT), physical adsorption, sweaty monolayers.Inhibitors are chemical substances added to a liquid to prevent corrosion or to control it at an acceptably low rate. They are used mainly in closed or circulating systems (1,2) and are selected for their effectiveness in protecting the specific metal or combination of metals in a given system. The corrosion of metals in aqueous solutions can be inhibited by a very wide range of substances (3-6) such as chloride, bromide, or iodide ions; carbon monoxide; and many organic compounds, particularly those containing elements of group V and VI such as nitrogen, phosphorus, oxygen, and sulfur. Organic compounds containing multiple bonds, especially triple bonds, are effective inhibitors. Organic compounds of high molecular weight (7), e.g., proteins and polysaccharides, also have inhibitive properties. This study is concerned with the evaluation of two synthesized cationic surfactants, i.e., alkyl mono-and dibenzoate triethanolammonium bromide (TEAMB and TEADB, respectively), as corrosion inhibitors for mild steel in an acidic medium (2 N HCl) at different doses. EXPERIMENTAL PROCEDURESSynthesis of alkyl mono-and dibenzoate triethanolammonium bromide derivatives. The synthesized inhibitors were described briefly in a previous study (8) as having the structures shown in Scheme 1. Corrosion inhibition measurement.A weight loss method was performed to measure the inhibition efficiency of the prepared alkyl mono-and dibenzoate triethanolammonium bromide derivatives for a mild steel specimen in a 2 N HCl solution. The composition of the mild steel specimen (wt%) was 0.2 C, 0.03 Si, 0.5 Mn, 0.8 P, and the remainder was Fe. The specimen was machined into a regular form electrode of 4 cm 2 cross-sectional area and 0.76 mm thickness. The specimen was sequentially abraded with di...

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