Film coating processes overview

Pan-coating can potentially be used to apply a film coat on any particulate material that can be confined to a coating pan and be coated. Beyond that, the applied coating system must be applicable to the critical process requirements such as particle size, coat solution viscosity, drying requirements, coat properties, and final product attributes. This section provides a general overview of applications and application considerations for pan-coating processes. 

Electrodeposition offers the facility to coat surfaces which are hidden from line of sight application techniques, such as spraying. Radiators are one such example, but electrodeposition can only apply the primer or base coat. Only one coat can be applied and it must be the first. The ability to deposit film in these hidden areas is known as throwing power . The more the coating penetrates these areas, the greater the throwing power of the coating. An overview of the electrodeposition process will now be considered. 

Table 51 shows an overview of pigments with luster effects. Effect pigments can be classified as metal platelets, oxide-coated metal platelets, oxide-coated mica platelets, platelet-like mono-crystals and comminuted PVD-films (Physical Vapor Deposition). Aims of new developments are new effects, colors, improvement of hiding power, increase of the interference color, increase of light and weather stability and improved dispersibility characteristics. Of special interest are pigments which are toxicologically safe and which can be produced by ecologically acceptable processes. 

An essential element of the CVD process is the chemical reaction that occurs to produce the coating/film. The precursors that constitute the chemical reactants must, of course, contain the chemical elements that will ultimately constitute the coating. In addition, these precursors must be stable at room temperature, react cleanly in the reactor without side reactions, not condense in the transfer lines, and be easily produced. The number of CVD reactions that are currently used is quite extensive and a complete listing of every reaction is beyond the scope of this review. However, a classification according to the method to activate the reactions for generic reaction type with specific examples is given in what follows. This will provide the reader with an overview of the diversity of applications of CVD. 

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