Anticorrosion Protection of Low‐Carbon Steel by the Eco‐Friendly Composition Based on Gum Arabic

Abstract

Inhibitory properties of an eco‐friendly composition based on gum arabic polysaccharide and citric acid salt–sodium citrate for corrosion prevention of low‐carbon steel in neutral environment was investigated. Corrosion resistance of low‐carbon steel in a 0.1% NaCl solution with and without composition after 3 and 24 h immersion was investigated by electrochemical and weight loss methods. The inhibitory composition with 0.5 g/L concentration was obtained by adding 0.25 g/L of gum arabic and 0.25 g/L of sodium citrate in 1L 0.1% NaCl solution. It was established that the inhibitory efficiency of the composition is enhanced with increasing concentration (0; 0.25; 0.50; 0.75; 1; 1.50; 2.0 g/L) and reaches a maximum at 2.0 g/L of each component. The protective effect of the composition is determined by the combination of two compounds of different natures, which have hydroxyl and carboxyl functional groups. The inhibitory ability of the composition is due to the dominant competitive adsorption between citrate anions with gum arabic and chloride ions on the steel surface. Adsorption of citrate and gum arabic on the steel surface corresponds to the Frumkin isotherm, and the Gibbs energy value was −12.25 kJ/mol, which indicates physical adsorption. The morphology and chemical content of the steel surface after immersion in a solution with an inhibitory composition were investigated by the scanning electron microscopy (SEM) and EDX analysis. The formation of a protective film based on gum arabic and citrate probably occurs by chelation, which effectively blocks the access of corrosively active Cl− ions. It was shown that the corrosion rate Km was 0.42·10−5 g/cm2·h and the inhibitory efficiency for protection of the steel was 80.4% after 24 h immersion in a 0.1% NaCl solution with composition.