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CORROSION OF STEEL AND ALUMINIUM

V.Ryan © 2019

 
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Corrosion takes place, when the surface of a metal reacts with its environment. For example, if steel is left in a moist, humid or wet environment, its surface forms ferric oxide, we call this rust. Another example is seen with the surface of aluminium. Over time, the surface of aluminium forms a layer of aluminium oxide. Although this is corrosion, once the layer has formed, it protects the rest of the aluminium from further corrosion. With steel, rust establishes itself and then continues to expand, weakening the metal over time.

 
 
 
 

Corrosion poses many problems for engineers and designers. Rust is not aesthetically pleasing and is not a desired outcome. In structures such as bridges, maintenance teams have a continual battle to protect the surface steel, with corrosion resistant paint, which creates a barrier between the steel and air/moisture. Corrosion can lead to structural failure and put lives at risk (see the image opposite). Corrosion is expensive to ‘fix’. Therefore, preventative measures, in terms of the application of finishes, is always a design and cost consideration.

Finishes to metals include: Paint, galvanising, chemical blacking, repeated application of a film of grease, anodising and even powder coating.

 
 
 
 
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