Corrosion protection of steel sheets by chitosan from shrimp shells at acid pH

The corrosion behavior of mild steel (MS) sheets in 0.5 M H₂SO₄ in the presence of chitosan extracted from shrimp shells (CSS) has been studied using electrochemical techniques. The optimum concentration (10 µM) of this carbohydrate polymer inhibited MS corrosion up to 85 % in the solution of the acid electrolyte. Results reveal that CSS reduced the dissolution of MS linearly with its concentration, and this reduction could be attributed to the interfacial formation of CSS film at the MS-electrolyte boundary. CSS is a mixed-type inhibitor and the shapes of Nyquist capacitive and inductive loops obtained from the impedance results could be associated with double layer reactions and relaxation of corrosive ions adsorption in the presence of CSS, respectively, at the MS/solution interface. Surface analytical studies with atomic force microscope, scanning electron microscope and Fourier transform infra-red also confirm the adsorption of CSS on MS.