Effect of Deposition Temperature on the Evolution of Texture, Grain Boundary Constitution and Corrosion Behaviour of Sn–Cr Coatings

Effect of deposition temperature on the evolution of microstructure and corrosion properties of electrodeposited SnCr coatings was studied. The coatings were electrodeposited at three different bath temperatures (15 °C, 30 °C, 45 °C). All the coatings were compact and contained tin and chromium oxide phases. Coating fabricated at lowest temperature (15 °C) exhibited the highest corrosion resistance. The polarization resistance values (R_p) obtained from the electrochemical impedance spectroscopy analysis were 9160, 3672 and 8212 Ω cm², respectively, for 15 °C, 30 °C and 45 °C coating. Electron backscattered diffraction analysis was conducted to correlate the electrochemical properties of the coatings with coating texture. The preferred texture changed from near (100) orientation to (201) orientation as the electrodeposition temperature varied from 15 °C to 45 °C. Grain boundary constitution of the coatings were sensitive to the deposition temperature. The fraction of low angle grain boundaries (LAGB’s) for the low temperature coating (15 °C) was 59.8 pct, while the fraction of LAGB’s for the coating fabricated at high temperature (45 °C) was 36.0 pct. The higher fraction of LAGB’s and lower energy preferred orientation (100) in case of 15 °C were responsible for its higher corrosion resistance performance.