Corrosion on alloy wheels – why does it happen?

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Corrosion of alloy wheels under the clear coat is “completely normal” and most often occurs due to improper maintenance of the wheel or incorrect winter storage.

Also known as “white worms” on alloy wheels – it is simply oxygen that corrodes the raw aluminum under the clear coat, and you cannot do anything about it, as the clear coat is “in the way” in terms of repairing/polishing the surface.

Practically, it occurs when oxygen/moisture gets under the clear coat and comes into contact with the raw aluminum surface.

Winter Storage
Many see the worst cases of corroded alloy wheels when they take them out again in the spring after winter storage – the fundamental problem here is “moisture,” i.e., humid air that attacks the raw aluminum under the clear coat – therefore, we always recommend that such types of alloy wheels be stored at a constant temperature in an insulated/heated room.

• Always store your delicate wheels in a dry room that does not have temperature fluctuations

Care and Maintenance
Other factors that can exacerbate the problem can be if you have used an acid or base-containing wheel cleaner (many make the mistake of thinking an acid-free wheel cleaner is “safe”) – We will soon have a blog post about wheel cleaners.

• Always use a PH-neutral wheel cleaner – Acid-free is not enough!
• Protect your wheels with a wheel sealant – then you won't need such harsh cleaning agents to clean

Road Salt – Never Drive Out of Season
Just like the wheel cleaner, the “salt” in Denmark is the natural “non-PH-neutral” in a Danish winter period – combined with often high humidity, we have a good cocktail here to “accelerate” problems with corrosion under the clear coat – therefore, it is important never to drive too early or for “too long” on wheels with polished surfaces.

Winter Suitable – NO!
Some sites that sell alloy wheels will show whether a wheel is winter suitable or not, and it is basically an expression of how delicate the “surface” of the wheel is. A non-winter suitable wheel (for example, with a polished surface) will be extra susceptible to damage from salt, moisture, etc.

Shortcut to Raw Aluminum
If the surface gets a stone chip, there is direct access to the raw aluminum, and this will also start the process, but often if you take good care of the wheels and follow the above, the wheels can easily withstand minor stone chips for many years without being damaged.

Alloy wheels with polished surfaces or similarly delicate surfaces can be a thin lacquer showing a diamond-cut aluminum structure or similar under the lacquer, which is much more delicate than fully painted wheels – this means there are some things you need to be extra aware of when storing and maintaining your alloy wheels.

Below we have shown a few examples of wheels with polished aluminum surfaces.

What types of surfaces will you find on alloy wheels:

• Painted / Lacquered wheels – Completely standard and used originally by Audi, BMW, Ford, etc.
• Powder coated – Stronger surface than “normal” painting
• Anodized – usually used to save weight, or on wheels to differentiate
• Diamond Cut – shiny aluminum with only clear coat on top
• Chrome – chrome-plated wheels are extra delicate on the surface and are a chapter in themselves.

Most often you will find that alloy wheels are made with a combination of these things, most often with Diamond Cut wheels you will fully paint the wheel first, then turn the Diamond Cut details off and then the wheel gets another layer of clear coat.

This also explains why the lacquer thickness on a Diamond Cut wheel is significantly more exposed, as it is thinner and has neither primer nor color underneath.