For many years, cars were fitted with steel wheels and hubcaps for decoration. Aluminium or magnesium alloy wheels were reserved for more expensive and sporty cars, since they were expensive themselves. Then came the mass-production of alloy wheels and they started to be seen on an increasing number of cars. Nowadays, they are usually fitted to most cars, apart from the most budget friendly cars, but powder coating has made them more colourful and durable.
So what is this process and is it any good?
Powder coating explained
Most aluminium alloy wheels are finished in a grey paint with a thick layer of lacquer to protect the relatively soft aluminium alloy from road damage. It makes the wheel almost look as though they are not finished at all and lets the silvery-grey of the aluminium show through, making it aesthetically pleasing without detracting too much from the form and colour of the car itself.
But as more people seek to make their cars their own, the wheels are increasingly becoming a target part for extra colour, either to reflect the overall colour of the car, or to make it anything but grey! Alloy wheel powder coating gives people the opportunity to do that quickly and cheaply.
Becoming popular about 40 years ago, powder coating is now used on many parts because it increases durability of the outer surface at a reasonable cost. While parts might look like they are painted, powder coating is a dry finishing process that uses finely ground particles of pigment and resin mixture that are electrostatically charged and then sprayed onto electrically grounded parts so that they stick to it. The charged powder particles adhere to the part and are held there until melted and fused into a uniform coating in a curing oven.
Powder coating tends to give a thicker, more resilient, and uniform surface that is resistant to many forms of casual damage, and is a much preferred – though more costly - alternative to simple painting. It has both advantages and disadvantages when applied to alloy wheels.
Advantages of powder coating
It is non-porous. Even paint and lacquers allow a small amount of moisture to get through them with time, passing through to the aluminium and starting to corrode it from the inside. Powder coated wheels do not suffer from the ‘bubbling’ that other finishes finally succumb to.
It is durable. Powder coating is a thicker, more hard wearing surface treatment, that can last as long as three times that of normal paints and lacquered surfaces.
Consistent covering. Because it is an electrostatic process, the powder coating mix it attracted to the surface in an even layer. Giving a consistent finish when baked. There is also no risk of drips and runs forming.
Quicker process. With the wheel prepped, the actual application and curing time is much lower than traditional painting and lacquering as there is only the application of the mix and curing operations to carry out.
Multiple materials. The powder coating technique can be applied to several different wheel materials including steel and stainless steel, as well as aluminium alloy.
Disadvantages of powder coating
It’s quite thick. If you have very intricate detail on your wheel, that application of the mix may dull it down and fill in small areas completely. Moreover, because powder coating is a fairly thick layer on the metal surface that can remove some of the definition of the wheel, it can sometimes lead to problems with your car tyres.
With low profile tyres in particular when the bead of the tyre won’t locate snuggly against the edge of the rim, leading to a slow leakage of air and the tyre eventually going flat. This can also dictate your tyre size to some degree.
Higher charge for small projects. Because it is unlike spray-painting, a supplier may charge you more if they don’t have anything else to cover with the same colour. Small batches are expensive.
It’s difficult to touch up. If you have powder coated rims that need some reworking, it’s actually better to have them cleaned right back and started fresh rather than trying to refresh small areas.
Unbalanced colour. While the coating tends to be of a pretty consistent thickness, once it has been cured, thinner sections may appear a slightly different colour to thicker sections.
Powder coating is a strong, resilient process that can make your wheels look great, but you have to be careful about how and where you use it, as the coating thickness can be a major problem.