It cannot be emphasised enough the importance of pre – treatment of surfaces prior to coating, failure to ensure correct cleanliness prior to any coating can lead to at best a poor finish and at worse the premature failure of the surface, leading to costly repairs.
One of the most important features to get right is the correct balance of cost over performance, all too often components can be over specified leading to expensive and uncompetitive processing costs, but more often than not under specification leading to premature failure.
There are a considerable amount of processes for pre-treatment prior to powder coating, but the following 3 are the ones mainly used for powder coating, each one has its own merits;
Degreasing can vary from a straightforward wipe with a rag soaked in a proprietary degreasing liquid, to quite complex ultrasonic vapour cleaning. The contaminated surface will be clean and dry fairly quickly and ready for painting almost immediately dependant upon the evaporation rate of the solvent, this method is a mixed blessing as the environmental issues can be a problem if not correctly administered, This system is the one to choose if cost and simplicity are important considerations.
Phosphate conversion coatings come in two basic types of zinc and Iron, both of these offer excellent durability, with the zinc phosphate coming out better for performance, and the Iron better for its more sympathetic environmental consideration, this system is the best for balance between performance and cost.
Galvanising is a loose term that most people associate with the spangle silver finish on fences and gates, but in reality it covers all metal surfaces covered with another metal - usually in order to prevent corrosion, more often than not the galvanised surface is zinc based. Because this is seen as a finish in its own right further coating can be problematic if not treated correctly, this system is the preferred one when performance is the main consideration.