Effect of benzaldehyde on the electrodeposition and corrosion properties of Ni-W alloys

The effect of different concentrations of benzaldehyde on the electrodeposition of Ni-W alloy coatings on a mild steel substrate from a citrate electrolyte was investigated in this study. The electrolytic alkaline bath (pH 8.0) contained stoichiometric amounts of nickel sulfate, sodium tungstate, and trisodium citrate as precursors. The corrosion resistance of the Ni-W-alloy-coated specimens in 0.2 mol/L H2SO4 was studied using various electrochemical techniques. Tafel polarization studies reveal that the alloy coatings obtained from the bath containing 50 ppm benzaldehyde exhibit a protection efficiency of 95.33%. The corrosion rate also decreases by 21.5 times compared with that of the blank. A higher charge-transfer resistance of 1159.40 Omega center dot cm(2) and a lower double-layer capacitance of 29.4 mu F center dot cm(-2) further confirm the better corrosion resistance of the alloy coating. X-ray diffraction studies reveal that the deposits on the mild steel surface are consisted of nanocrystals. A lower surface roughness value (R (max)) of the deposits is confirmed by atomic force microscopy.