Complex coating systems conversion layers

COMPLEX COATING SYSTEMS Pretreatment Conversion Layers... 

Contemporary protective coatings have, as a rule, a quite complex structure, which is, in turn, closely related to the underlying substrate and to the specific demands on the corrosion resistance. However, it is possible to point out some common elements present in the vast majority of protective coatings. A typical protective coating is a layered system consisting of (i) a pre-treatment layer or conversion layer (ii) a primer layer and (iii) a top-coat layer (Fig. 10.1). Quite often, a layer of electrochemically more active metal (Zn, Cd, etc) is deposited on the top of a metal or alloy substrate to provide additional cathodic protection (Brock etal, 2009). 

Conversion coating and e-coating are simple, low-cost and scalable coating schemes for the protection of Mg alloys. However, the information here has been based on a limited number of reviews and therefore does not contain all the information in the public domain. In addition, the current coating schemes are mostly complex, multi-layer systems that incorporate many different technologies and must be conducted very carefully in order to achieve optimum results. 

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