Effect of ethyl vanillin on ZnNi alloy electrodeposition and its properties

Abstract

The bright ZnNi alloy coating on steel surface was prepared by elctrodepostion technique using brightener ethyl vanillin (EV). To know the influence of brightener on deposition and dissolution behaviour of ZnNi alloy, cyclic voltammetric studies were carried out. FT-IR spectroscopic evidence was given to confirm selective adsorption of brightener on steel surface. The brightener enhances current efficiency and throwing power of plating bath during coating. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses in presence of brightener confirmed the change in surface morphology, phase composition and preferred orientation of ZnNi coating. In presence of brightener, nickel content of the coating was reduced at higher current density and thickness. In addition, deposit properties like appearances, hardness, adherence, ductility and corrosion resistance of ZnNi alloy deposits were also improved in bright deposit. Simultaneously, effect of deposition current density and thickness on corrosion behaviour of coating was examined.

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

“…In Table 2, a high protection efficiency (PE(I)) of 95.27% is obtained at 50 ppm benzaldehyde, indicating that the presence of aldehyde in the bath is useful in attaining a uniform crystalline structure. The E corr value at 50 ppm benzaldehyde shifts toward to the more noble direction, whereas it shifts toward to the less noble direction at other concentrations, suggesting that corrosion resistance decreases with increasing aldehyde concentration [16]. Notably, a high polarization resistance value of 1697.8 Ω·cm 2 is obtained for Ni-W alloy coatings at 50 ppm benzaldehyde in the 0.2 mol/L H 2 SO 4 solution, which implies a greater protection efficiency for the deposit as compared to that obtained from the bath without aldehyde (100.0 Ω·cm 2 ).…”

Role of the newly synthesized brightener in modification of surface properties of Zn-Ni alloy electrodeposited on steel substrate

“…In the absence of SC in the optimized bath solution, four oxidation peaks (A 1 , A 2 , A 3 and A 4 ) are seen in the voltammogram. The multiple peaks detected during the electrochemical oxidation of alloys are due to dissolution of metals in the alloy via different intermediate phases [13]. Four anodic dissolution peaks for Zn-Ni alloy correspond to the dissolution of three phases in zinc-nickel alloy deposit.…”

“…The bath constituents and operating conditions were optimised by Hull cell experiments to get a bright deposit over wide current density range [13]. The plating bath composed of zinc sulphate, nickel sulphate, sodium sulphate, cetyltrimethylammonium bromide (CTAB) and boric acid.…”

“…On reversing the sweep direction, two current crossovers appear in the cathodic region. The more cathodic potential at which the crossover occurs is known as the nucleation overpotential (E η ) [13]. The second crossover at zero current region (-1.02 V) is known as crossover potential (E co ).…”

“…As also shown in Figure 1, in presence of SC, the plating bath cathodic potential (E 2 ) was shifted negatively to -1.41 V, which indicates that SC acts by adsorbing on the cathodic surface. Adsorbed SC created a barrier near the electrode surface that inhibits the discharge of metal ions, leading to a decrease in the grain size of the deposit [13]. The voltammogram in Figure 1 also shows two broad anodic peaks (a 2 and a 4 ) at -0.73V and -0.25 V. The first broad peak (a 2 ) corresponds to oxidation of zinc from the η-phase (zincrich phase) and the second broad peak (a 4 ) corresponds to the dissolution of nickel from η and γ phases.…”