Corrosion inhibition of mild steel in acidic medium by polyacrylamide grafted Guar gum with various grafting percentage: Effect of intramolecular synergism

•GG-g-PAM with various %grafting shows high η for corrosion of mild steel in HCl.•Synergism exists for adsorption of GG and PAM units of GG-g-PAM on alloy surface.•Possible binding sites of copolymer are assigned following FTIR spectroscopy.•At high %grafting and after long exposure in acid medium, η gradually decreases.

Polyacrylamide grafted guar gum (GG-g-PAM) with various grafting levels has been tested as potential green inhibitor against corrosion of mild steel in 1 M HCl. Upto 86% grafting, grafted copolymer maintains inhibition efficiency higher than 90% for about 50 h of exposure. Grafted polysaccharide behaves as mixed type inhibitor and forms an inhibitive layer on the metal surface following Langmuir adsorption isotherm. GG and PAM moieties are found to synergistically influence each other on adsorption and subsequent corrosion inhibition. FTIR spectroscopy reveals the possible binding sites of grafted polymer during adsorption on metal surface.