Powder coating is a fast and cost effective method of painting predominantly metal substrates. The surface to be coated should be free of rust, oil, grease and moisture, in addition it should also be subjected to a surface preparation which is in line with the material to be coated. This can range from blast cleaning which removes deep surface contaminants such as rust, to etching on aluminium and iron phosphate on steel. The most basic of preparation is neutral detergent cleaning followed by a wipe down with a tak cloth to remove dust particles but this is only advisable in circumstances where the long term longevity of the coating is not a consideration.
Typically the powder is applied by electrostatic spray strait from the box. The item is then heated in an oven to between 180 & 200 degrees Celsius (metal temperature) for 10 minutes. Other curing parameters are available but this criteria meets 90% of applications. Once out of the oven & cool the item can be handled, packed or put to use.
In some quarters it is perceived that powder is by default a super durable coating designed to withstand any environment & unlimited abuse. Like any paint it has it’s limitations and is subject to the quality of preparation as much as the quality of the powder itself.
These days most powder coatings are Polyester. In general, polyester resin is exterior durable, highly flexible & powders are readily available in a host of colours. This said, if your item is going to spend all or most of it’s time outside the Polyester powder coating used must be made using colour fast pigments. If in doubt ask for Architectural Grade Polyester, do not use Industrial Grade Powder Coatings as these will degrade fairly rapidly particularly in a bright colour. If you’ve ever seen faded railings or playground equipment this is usually why.
Until a decade ago many powder coatings where Hybrids, these are a blend of polyester and epoxy resins & although the cost savings which produced a flurry of this type of powder in the 80’s & 90’s are now negligible, these hybrids are still in production and used predominantly on mass produced goods for the lighting industry, supermarkets & domestic appliance markets. Epoxy Polyester Powders still have most of the flexible properties of their polyester cousins and the epoxy content gives the coating a degree of impact & chemical resistance but the epoxy also means they are not suitable for external applications. These Hybrid Powder Coatings still find their way into the general industrial market but usually in the form of structured finishes such as “Leatherette Powders”
Epoxy powder coatings are in very short supply and colour availability is extremely limited but you can have something made bespoke if you are in desperate need of the adhesion properties or abrasion resistance they offer & are prepared to pay the premium which accompanies special makes. Epoxies usually have fairly specialist applications such as chemical resistance, they are not flexible and can not be used externally.
Some items you could paint using powder coating:
Iron garden furniture, bike frames, gates, railings, balustrades, door & window furniture, household objects, children’s play equipment, (this must be coated in a certified toxic free powder).
Some items you should not consider powder coating:
Marine equipment, swimming pool equipment, items to be submerged, cast iron bath tubs, alloy wheels (unless over coated with a durable wet lacquer) exhaust systems, potable water receptacles, cooking utensils.