Experimental and quantum chemical studies on the corrosion inhibition performance of water soluble chitosan derivatives for mild steel in acid medium

Abstract

Mild steel is the world s most widely produced material due to its versatile applications and cost-effectiveness, yet it is more prone to corrosion. The surface treatment of the mild steel in industries to remove rust, scale, or other contaminants make use of pickle liquors composed of concentrated acids containing corrosion inhibitors. These corrosion inhibitors, the first line of defense against corrosion, have an increasing demand in the global market. The key benefit of corrosion inhibitors is that it allows the use of low-grade steel in the place of costly alloys. Besides, it is simple, flexible, and compatible to use in aqueous environments. Chitin found in the exoskeleton of crustaceans is the second most abundant natural biomacromolecule. The low biodegradability of chitin has raised major concern in the seafood processing industry as the waste shells generated are 6 to 8 million tonnes globally every year. The deacetylated product of chitin is chitosan, and the conversion is said to be economically feasible, as well as the derived products possess versatile applications. The structure of chitosan reveals the presence of electron-rich, reactive hydroxyl groups, and the free amino group that provides avenues for its modification through chemical reactions even under mild conditions. An improved solubilities and physicochemical properties can be achieved through chitosan modification resulting in effective adsorption on the metallic surfaces and improved corrosion inhibition efficiency. The present investigation deals with the modification of chitosan using a highly antioxidant ferulic acid, potentially coordinating disodium EDTA salt, and long alkyl chain containing surfactant namely sodium lauryl sulphate. The three modified chitosan polymers referred as FCS, DSEC and SLC are characterized using spectral studies, thermal analytical methods, zeta potential, particle size analysis, SEM and EDS studies. The modified chitosan amides were then evaluated for corrosion inhibition efficiency using weight loss