Aluminium and Galvanic Corrosion

From its ranking on the scale of potentials (Table B.1.1), aluminium is more electronegative than most common elements steel, stainless steel, cuprous alloys, etc. Whether in mechanical applications, building, electrical engineering, ship building, heat exchangers or circuits of aqueous liquids (fresh water or seawater), it is common to find heterogeneous assemblies in which there is contact between aluminium alloy components and components made of other metals. 

It is not possible to use aluminium only in homogeneous systems consisting in a single aluminium alloy, for both technical and economic reasons. Here are two examples  

The first example is a ship. The propeller shaft is very often made of stainless steel, because for reasons related to mechanical resistance, it is impossible to manufacture it in aluminium alloys, except perhaps in 7075. The propeller is very often made in brass, and sometimes in cast aluminium, for small crafts. This has not been a hindrance for the construction of ships in aluminium, even very large ones, because it is possible to control galvanic coupling in the hull. 

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