Interfacial impedance spectroscopy on electroplated nickel electrodes in chloride and sulphate solutions

The corrosion behaviour of the as-plated three different nickel electrodes has been investigated in 5 percent NaCl and 6 percent Na[2]SO[4] solutions by using impedance Spectroscopy technique. Ladder network equivalent circuits and simple equivalent circuits have been used to explain the electrochemical behaviour of the nickel electrodes in the above solutions. Analysis of the impendence spectra showed that the impedance parameters depended on the electrode type and the applied potential in chloride and sulphate solutions. In the chloride solution the three nickel electrodes exhibited rapid pitting corrosion while in sulphate solution the electrodes were rendered passive with very low corrosion rate

Galvanic corrosion of electroplated nickel coupled electrodes in chloride and sulphate solutions

The free corrosion potential of the as-plated pure nickel [P-Ni], semi bright nickel [SB-Ni], bright nickel [B-Ni] and dispersed nickel [D-Ni] electrodes were measured in 5 percent NaCl and in 6 percent Na[2]SO[4] solutions. It has been found that there are a potential difference in the free corrosion potential of these electrodes when they are immersed in chloride or sulphate solution. The galvanic current and the coupled potential [mixed potential] for the couples of different as-plated nickel electrodes were determined in chloride and sulphate solutions. The value of the galvanic current depended on the mixed potential, type of nickel couples as well as on the solution type. SEM observation confirmed the presence of pitting corrosion attack on the more active member of the as-plated nickel couples in chloride solution. Impedance spectroscopy of as-plated nickel electrodes in chloride and sulphate solution under potentiostatic showed that the charge transfer resistance of the as-plated nickel electrodes indicated the presence of pitting corrosion attack in chloride solution while passivation occurred on the electrodes in the sulphate solution

Corrosion behaviour of different nickel layers electroplated from watts bath

3 layers of semi-bright nickel [SB-Ni], bright nickel [B-Ni] and dispersed SiO2-containing nickel [D-Ni] have been prepared from Watts electroplating bath with some organic additions. The influence of the bath additives on the free corrosion potential of each as-plated nickel layer has been examined in 5% NaCl and 6% Na2SO4 solutions. Exposure time in the air after nickel layer preparation assisted the oxide film formation on semi-bright more than on bright nickel surfaces. The anodic and cathodic polarization curves of as-plated nickel layers in chloride and sulfate solutions were investigated by using the potentiodynamic technique. In chloride solution, nickel layers exhibited pitting corrosion. The critical pitting potential, E pit, decreased in the order; D-Ni > B-Ni > SB-Ni, while in sulfate solution, the nickel layers were passive

Effect of metal cations on the corrosion behavior of Ti, Al, Cu-Ni and Al-Brass in chloride solutions

The effect of addition of Cu2+, Co2+, Cd2+ and Fe3+ cations to chloride solutions on the potentiodynamic polarization of Al, Ti, Cu- Ni [66-34] and Al-brass was investigated. The study was confirmed by the XPS examination. It was found that Fe3+ ions cause an increase of the corrosion current, i.e. corrosion rate for Al, Ti and Cu-Ni alloy and a decrease at low concentrations [10-5 - 10-4 mol dm-3] for Al-brass. Cu2+ and Co2+ cations increase the corrosion rate of the metals, while inhibition of alloys is manifested at low cations concentration. Cd+2 cations behave as an activator but show slight inhibition at low concentration for Al-brass. The results were interpreted on the basis of exchange reactions causing deposition of the metal cations on the surface of the electrode