Oxidation galvanic effects

Galvanic effects If niobium is cathodic in a galvanic couple the results can prove disastrous because of hydrogen embrittlement. If niobium is the anode in such a couple it anodises so readily that no damage occurs and the galvanic current drops to a very low value due to the formation of an anodic oxide film. 

Pierron et al. (2005) found that oxide layers up to 80 nm thick could form at room temperature during manufacturing due to a galvanic effect between highly doped n-type Si and Au. Electron microscopy confirmed that the layers were porous and composed of Si02 covering Si cores. Concentrated HF solutions are usually associated with oxide dissolution. However, the measured... 

Pierron ON, Macdonald DD, Muhlstein CL (2005) Galvanic effects in Si-based microelectrome-chanical systems thick oxide formation and its implications for fatigue reliability. Appl Phys Lett 86 211919... 

Lastly, another effect by alloying platinum with a foreign transition metal is discussed in the literature. The galvanic effect comes from the fact that the transition metals are more easily oxidisable than platinum. They allow for the protection of the platinum surface, preventing it from oxidation, and only metallic platinum is active for the oxygen reduction reaction. 

Anodic oxide formation Lakhiani and Shreir have studied the anodic oxidation of niobium in various electrolytes, and have observed that temperature and current density have a marked effect on the anodising characteristics. The plateau on the voltage/time curve has been shown by electron microscopy to correspond with the crystallisation of the oxide and rupture of the previously formed oxide. It would appear that this is a further example of field recrystallisation —a phenomenon which has been observed previously during anodisation of tantalum" . No significant data on the galvanic behaviour of niobium are available however, its behaviour can be expected to be similar to tantalum. 

Sulfamic acid (HOS02NH2). Clean at only 120 °F (49 °C) for cast iron and up to 140 °F for marstenitic SS (60 °C). It is not suitable for galvanizing or aluminum over 150 °F, but it is suitable for copper, brass, and SS. Sulfamic acid tends to be used only in small systems because of its relatively high cost. It is a ciystalline solid and so is easily transported. Additionally, in the diy form it is relatively safe and has a negligible effect on skin. Typically, it is used at 10% strength, and when 5% sodium chloride is added, it is reasonably successful at dissolving ferric oxide. 

Oxidation of a metal or alloys to its (lower energy state) oxides or cations. In effect, the wastage or other damage to a metal caused by one or more of several types of chemical or electrochemical reactions. Takes many forms such as galvanic, crevice, pitting, underdeposit, and biologically induced corrosion. 

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