After removing the old coating from an aluminum rim, its actual condition is often visible.
Some rims have only slight oxidation and surface tarnish. Others have deep corrosion spots and pitting that has developed under the paint over many years.
Automatic shot blasting handles the first group well. However, with the second group, it's important to understand what's actually happening to the material.
Light corrosion and tarnish
If corrosion occurs on the surface, shot blasting can clean and dull the aluminum very effectively.
The abrasive removes loose corrosion products and prepares an even surface for the next steps.
In such conditions, the machine has a big advantage because the entire rim is processed in a repeatable manner.
Deep pitting is not just dirt
The situation is different when corrosion has been developing deep into the aluminum for a long time.
Pitting is not a layer found only on the surface.
At such a point, some of the material has already been attacked.
Therefore, completely „leveling” such a point would require machining the surrounding aluminum as well.
This is a very important distinction.
Cleaning the corrosion does not automatically restore the surface to the condition of a new rim.
Why is it not enough to extend the blasting time?
The machine affects a large part of the surface evenly.
So let's assume that the entire rim is already properly prepared, but there is a deep corrosion spot on one spoke.
The cycle can be extended.
The problem is that for those extra minutes, the abrasive continues to affect all the areas that no longer require intensive cleaning.
As a result, attempting to remove one difficult point can lead to unnecessarily aggressive treatment of the entire surface.
Why does a hand-held sandblaster have an advantage here?
In a cabin sandblaster, the operator can see the problematic area and direct the jet exactly to that spot.
The remaining parts of the rim do not need to be further processed at this time.
Therefore, after automatically preparing the entire surface, it may be wise to perform a check and then manually correct only the areas that require additional work.
automatic → control → manual spot correction.
Why might pitting still be visible after shot blasting?
Because a shot blasting machine is a surface treatment device, not a device for rebuilding aluminum.
It can clean up corrosion and prepare the metal, but if a deep cavity has already occurred, its geometry may still be visible.
This does not necessarily mean that the device is malfunctioning.
It may simply mean that we are dealing not with a surface coating, but with actual damage to the material.
Automatic surface cleaner, manual cabin for difficult spots
In practice, combining two ways of working works very well.
The automatic shot blasting machine prepares the vast majority of surfaces without the involvement of an operator.
Once the cycle is complete, the rim is inspected.
If a single spot requires additional cleaning, the operator touches it up manually rather than intensively re-machining the entire rim.
This approach allows you to maintain the efficiency of the machine while maintaining control over areas that require individual attention.