In this work, water-soluble poly (N-vinyl imidazole) grafted carboxymethyl chitosan composite (CMCh-gPVI) has been synthesized from chitosan, characterized and deployed as a corrosion inhibitor for API X70 in 1M HCl. CMCh-g-PVI composite significantly reduced the corrosion of X70 steel when compared with equimolar concentration of chitosan and carboxymethyl chitosan in the same medium due to the formation of stable protective polymeric films on the metal surface. This was confirmed by means of scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. In depth electrochemical corrosion study was conducted after chloride treatment using potentiodynamic polarization and electrochemical impedance spectroscopic techniques on precleaned substrates. This polymer composite may have a future as an efficient ingredient in corrosion inhibitor formulations for metal surface treatments. (C) 2018 Elsevier Ltd. All rights reserved.