Relation of degree of substitution and metal protecting ability of cinnamaldehyde modified chitosan

Considering the advancements in the applications of biopolymers such as Chitosan due to its biocompatibility, biodegradability and non-toxic properties, five different Chitosan cinnamaldehyde Schiff bases (Chi-Cn1-5) using chitosan and cinnamaldehyde as monomer units were synthesized by varying the degree of substitution. Further, anti-corrosion property of all these biopolymers against corrosion of mild steel was studied in 0.5 M H2SO4 by gravimetric and electrochemical methods. Scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), atomic force microscopy (AFM), scanning electrochemical microscopy (SECM) and X-ray photoelectron spectroscopy (XPS) were utilized to affirm the adsorption of studied biopolymers at the metal/electrolyte interface by inhibiting mild steel (MS) corrosion. The shift (< 85 mV) in the value of corrosion potential by the presence of biopolymers affirmed their mixed-type nature of inhibition. The results depicted that Chi-Cn5 performs best against corrosion of mild steel in acid medium among all other biopolymers due to its maximum degree of substitution.