Nickel alloys anodic behaviour

Fig. 3.36 Effect of nickel on the anodic behaviour of iron alloys in 1 N H2SO4 at 25°C. Curve 1 Fe curve 2 Fe-lONi Curve 4 Ni (after Beauchamp )...

During recent years a considerable amount of information has been published on the anodic behaviour of nickel alloys. The data include studies both of binary alloy systems in which nickel forms the major alloying component and of more complex commercially produced nickel alloys. The data are sufficiently numerous to permit a rational and fairly complete interpretation of many of the corrosion-resistant properties of nickel alloys on the basis of their anodic behaviour. 

Table 4.24 Influence of alloying on anodic behaviour of nickel...

The influence of minor alloying elements and the effect of formation of other phases on the anodic behaviour of nickel alloys are thus not negligible and should not be ignored. 

A metal hydride battery similar to the nickel-cadmium battery has been developed by Sharp corporation. The battery is shaped in the form of a button of 20 mm diameter and can give 1.2 V. The anode in the battery is made of La-Ni-Sn alloy hydride, and the cathode is nickel oxide. Potassium hydroxide solution in polyamide-resin is the electrolyte. The battery exhibits high energy density (i.e.) 1.5 to 2.0 times that of the Ni-Cd battery, good cycling life and superior low temperature behaviours. 

As the NDE is a phenomenon due to the unique electrochemical behaviour of Mg alloys, the error caused by the NDE effect as discussed above is not present in steel, nickel, or copper galvanic corrosion. Apart from the NDE-induced error, another source of error is that anodic polarization or the galvanic current does not always reflect the real galvanic corrosion rate of a metal. This is particularly true for any metal under weak anodic polarization. It is well known that ... 

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