Galvanised steel is a common form of steel used in transport and construction applications. A zinc layer acts as a sacrificial anode and protects the underlying steel against corrosion. An alternative to this product is the use of aluminized steel in which the aluminium layer gives improved functional properties, such as a higher thermal stability and the possibility of having a more decorative surface appearance. For aluminium as a bulk product it is known that a compact, inert and passivating layer is formed spontaneously at the surface, giving inherent good corrosion properties to the metal. However, the object of this study is a thin (20-30 urn) hot dipped aluminium layer formed on top of a steel substrate. This layer contains Al-Fe, Al-Fe-Si and/or Mg-Si precipitates (depending on the aluminium hot dip bath formulation) and consists of several sublayers: an interdiffusion layer between the steel and the aluminium, an aluminium alloy layer and an oxide layer. The properties and behaviour of such layers have been only fragmentarily studied.
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