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

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 ID/IG 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 (Rp ~ 40.23 Ω.cm2) that is drastically enhanced in the case of graphite–chitosan composite coating (Rp ~ 4327 Ω.cm2). 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.