I am getting a white dust in my car, coming from the air vents and landing all over, mostly on the dashboard. After searching about this, it seems that it could be caused by the fins of the air conditioner evaporator oxidizing (for whatever reason).

I recently bought the car (used), and I before I claim fixing/compensation from the dealer I want to have proof that it is in fact aluminium oxide, or else I expect that they will try every other alternative (=cheaper) explanation possible without getting to the root cause (seen this sooo many times).

So now I'm wondering if there is any reasonably cheap way to test and verify that the dust particles are aluminium oxide?

  • $\begingroup$ Check and see if your car has an interior cabin air filter (not the one in the engine). Sometimes they are in places like the glove box and are difficult to change. The previous owner may have neglected to do this. $\endgroup$ Mar 6, 2023 at 9:14
  • 1
    $\begingroup$ XY problem: What difference would the material make to getting the problem fixed? Even if it were aluminum oxide, not likely, either the dealer resolves it -- or not. Could be they used a power-washer on an aluminum part, e.g., to remove smoke smell from previous owner, and it corroded a bit. Whether the surface releases dust from Al2O3 or remains of detergent, the dealer would still have to fix it the same way. $\endgroup$ Mar 6, 2023 at 15:50
  • $\begingroup$ @DrMoishePippik In theory, yes. In the real world, things get more complicated. I've had numerous situations where I have a strong suspicion of the cause of a problem, but of course the responsible party will try various cheaper methods of "fixing" it and claim "Now it's fixed!" only to have the problem still remain. This creates unnecessary time, work, expense and irritation. I find it's often better to find proof of the root cause of a problem beforehand to avoid ending up with various "fixes" that might even cause new problems or make the original one worse... $\endgroup$
    – Magnus
    Mar 6, 2023 at 16:00

1 Answer 1


Aluminium forms a protective oxide layer that is strongly associated with the metal. Therefore, I doubt what you are seeing is actually aluminium oxide. Air probably wouldn't be able to disperse if.

In the case that I am wrong, though, there are several ways you can go about identifying whether or not the substance is aluminium oxide.

The first thing I would try is to drop in some water. Does it dissolve? If it does, definitely not aluminium oxide.

Firstly, since you wanna use this for insurance you wanna have it absolutely foolproof. You can subject a sample to mass spectrometry analysis. The downside is that it is expensive and you need to find a lab willing to analyse your sample.

Secondly, which is much more crude, you can subject it to metals and measure whether a reaction will occur or not. This can pinpoint where it is on the reactivity series, thus identifying the compound. For example, it may react with magnesium but not manganese. And this doesn't prove there is an oxide. It just proves it is an aluminium compound.

Research the reactivity series and redox reactions.

Thirdly, and this is also expensive, you can measure the melting point.

There are definitely other methods to doing this.

But I'm not sure this is a good idea in the first place. I don't think running a chemical analysis is a good way to make an insurance claim, but there is your answer.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.