Submerged or Embedded Structures

Some structures are permanently immersed in water or seawater such as a hull in aluminium with water points made in stainless steel, heat exchanger circuits in copper-nickel, scraper bridges in settling basins of water-treatment plants, etc. 

Galvanic corrosion also develops at improtected heterogeneous contacts that are embedded in the soil (see Chapter G.l). 

Zones that permanently retain humidity such as low points, basins, i.e. the hidden recesses where wet dust or mud accumulates, are sites where galvanic corrosion may develop. This happens especially in hidden recesses of vehicles at bolted or riveted assemblies between steel and aluminium where mud projected from the road may accumulate. 

All galvanic corrosion couples wiU be effective, including couples with stainless steel. Whatever the metal in contact with aluminium, it will be necessary to neutralise the coupling in order to avoid galvanic corrosion, which otherwise will be unavoidable. 

As mentioned above, in the case of an assembly with steel, the accumulation of corrosion products (alumina) may slow down or even stop galvanic corrosion. However, sometimes this happens only after serious damage to the aluminium parts has already occurred. 

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