Corrosion resistance performance of electrophoretically deposited graphite-chitosan composite coating on copper

Abstract

Development of graphite and graphite-chitosan composite coating on copper (Cu) substrate is carried out using electrophoretic deposition. Further, post-treatment is done using ethanolic solution of 20 wt% methyl hydrogen polysiloxane (KF-99) to improve coating adhesion with the copper substrate. The corrosion resistance of the post-treated coating is examined in 3.5 wt% NaCl solution. Field-emission scanning electron microscope reveals that the addition of chitosan leads to densification of the coatings. A reduction in the I-D/I-G ratio of the graphite-chitosan composite coating compared to graphite coating implies a decrease in the defect in the coating. An increase in corrosion potential of 0.29 V is noticed for graphite-chitosan composite coating compared to pure copper, i.e., -0.02 V. The corrosion rate is reduced to 34% for graphite coating (0.070 mmpy) and 51% for graphite-chitosan composite coating (0.050 mmpy) as compared to pure copper (0.102 mmpy) substrate. The pure copper substrate shows the lowest polarization resistance (R-p similar to 40.23 Omega.cm(2)) that is drastically enhanced in the case of graphite-chitosan composite coating (R-p similar to 4327 Omega.cm(2)). Enhancement in the corrosion resistance of the graphite-chitosan composite-coated sample is attributed to the formation of a protective barrier layer of SiO2 and chitosan, which acts as an obstacle to ion transportation between the copper substrate and NaCl solution.