Summary for powder coating for iron castings Discussion
Powder coating for iron castings is discussed as a finish that can provide color and gloss, but the thread warns that powder coating alone may not deliver enough rust protection. Thomas Brown asks for a coating that resists rust and offers a high-gloss finish in many colors. The answer advises that if the casting will be exposed to weather, a pretreatment and possibly galvanizing before powder coating may be needed, with zinc phosphate mentioned as a suitable pretreatment. For outdoor UV exposure, polyester powder is recommended; for chemical exposure, epoxy powder may be better. However, the answer cautions that epoxy should not be used outside in sunlight because it tends to chalk. The key point is that powder coating is only barrier protection, so any break in the coating can allow corrosion to start.
Q. I am looking for a suitable powder coating that will not only protect it from rust but also offer the ability for a high gloss finish in an array of colors.
Thomas Brown
iron castings – Dallas, PA, US
2004
A. Powder coating on its own might not give the corrosion protection you desire. Is the part exposed to weather? If so then you need more than just PC. Perhaps galvanize first then PC over top after suitable pretreatment such as zinc phosphate. If exposed to UV (out doors) then polyester powder might be good. If exposed to chemical attack, then epoxy powder. But don’t use epoxy outside in sunshine – it tends to chalk. Powder coating is only a barrier protection, and any perforation of the barrier will see corrosion.
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
