Conversion coatings anodized aluminium

Other important metal finishings to protect against corrosion are conversion coatings such as anodization (especially for aluminium), electroless plating, and electrophoretic painting. The first is done to form a passive layer, and is described in greater detail in Section 16.4. 

Conversion coatings offer many of the features identified as being desirable on a properly pre-treated metal surface consequently, they have been applied to a range of metals for the enhancement of structural adhesion. A number of studies have demonstrated that properly optimized conversion coatings are comparable to the anodic oxides in terms of providing durability with aluminium.Other studies have demonstrated variable adhesion performance with conversion coated aluminium adherends. A recent study has shown phosphated medium carbon steel to give better bond durability than grit-blasted and silane-treated material. ... 

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