How To Protect Alloy Wheels From Corrosion
Posted on: 01/10/2014
When you stop to consider what the average alloy wheel goes through, it’s remarkable that they stand up to the punishment they do.
Baking in the sun, to frozen in winter, soaked in water made more reactive by the roads being salted.Then there’s the pressures exerted by carrying the weight of the vehicle, revolving hundreds of times per minute, absorbing shocks and a myriad of complex cross-stresses when turning corners, or negotiating rough terrain.
The good news is, alloys don’t rust. Aluminium, the main component in alloys, is actually a highly reactive metal but, on exposure to the atmosphere, it instantaneously creates an oxide layer that then protects it from further corrosion.
Pretty good then, huh and far better than a steel equivalent that does rust. Well, yes for sure, but it is a little more complicated than that. Isn’t it always?
One of the things aluminium does react to is iron. And, one of the components in car brake pads is iron. Under braking, the pad obviously comes into contact with the brake disc, slowing the car down. In doing so, the disk and pad rapidly heat up and the pad, being the softer of the two, gradually wears down. That’s the agreement made in engineering terms, so the owner only needs to replace the cheaper, disposable pads, rather than the more expensive discs every time.
But as the pad wears down, it throws hot specks off, some of which inevitably land on the wheel rim. This explains the majority of the dark brown or black dust to be found on your front wheels. It’s a concoction of tiny bits of metal, brake disc compound and the resin used to bind it all together; a pretty toxic combination for your alloys.
The reason is that the resin, now reheated to melting point, flies off the pad and then sticks itself to the next thing it comes into contact with. In the case of your wheel, in that first impact, it can burn through the protective coat on your rim and embed itself into the very surface of the metal itself, before re-setting, as it cools down. This has the effect not only of puncturing a small hole in your rim’s defences, but also of dragging with it a small quantity of iron; Kryptonite for your aluminium.
This in turn sets up a chemical reaction between the iron and the aluminium, hence your wheel corroding. In fact, anything that removes the wheel’s protection, such as curbing, UV light breaking down the coating, or the wear and tear of driving, will expose the wheel to ever greater causes of corrosion- air, water, salt and reactive chemicals.
So although it won’t rust as such, it will corrode over time, if it’s not looked after and this will impact on the rim’s ability to seal with the tyre correctly, meaning a consistent loss of air pressure. And it looks rubbish.
So. How can you best counteract this sad state of affairs? Well, it is possible to buy brake pads that don’t contain iron. They may be more expensive and they may not even be made for your make and model. But they will help in reducing the attack from your brakes, even if they don’t prevent the resin from burning through.
There are plenty of proprietary wheel protection brands out there, like ProtectaClear for instance, but the first job will be to comprehensively clean the wheel. Use soap and water on a cool wheel and spend time getting rid of the dirt and grime, paying particular attention to the hard to reach places. Ensuring the wheel is clean will prevent you from sealing in any potential cause of future corrosion. Avoid using cleaners that are overly harsh or abrasive, as these will also impact on the life of your alloys.
Once thoroughly clean and dried, apply the chosen sealant and again allow it to dry, then reapply as per manufacturers instructions, applying two or three coats. Thereafter, wash the wheels regularly, to prevent a build up of potentially corrosive dust and compounds from eating away at them and check them regularly for any signs of damage.