bead blasting wheels

["Terry Folland" <folland@xxxxxxxxxxxxxx>]

With the current discussion on wheel stripping i thought i would pass on a
recent experience.
I recently aquired a set of campagnolo wheels for my 74gtv, they had
previously been painted in gold over the original silver and were in need
of stripping.
I took them along to a local powder coating business who also do bead
blasting and asked for there advise, they suggested that i just have one
wheel done to see what they were like under all that paint before deciding
what to do.
I called the next day and they said they had stripped one wheel and the
results were excellent, and suggested i have this powder coated in clear as
they had very good results restoring newer mag wheels like this, they also
suggested i collect the wheel and have some gutter rash on the edge of the
rim repaired before powder coating.
I called to collect the wheel a week later to have it repaired and was
suprised to see it had tiny black spots forming all over the surface, when
i pointed this out they said it was perfectly clean after stripping and
something might have been spilled on it afterwards and they would strip it
again for free after it was repaired and powdercoat it straight away.
Several weeks later i finaly returned the wheel after repairing it but by
now the black spots had grown to form a spider web like pattern all over
the wheel.
The wheel was bead blasted and powder coated immediately and the finish was
very good apart from some bubbling in the center of the wheel, this was
caused by gas escaping through the alloy when heated to set the powder
coating.
We decided to try another wheel, this was stripped then pre heated to
remove the gas then powder coated immediately this resulted in reduced
bubbling but still not good enough.By the time the second wheel was
finished the black spots were growing under the powder coating on the first
wheel and now several months later it is so bad the coating is being lifted
off by the [corrosion?] underneath, and there are finger prints clearly
visible.
Wheel number two is still as good as the day it was done.
The powder coaters have never come across this before so i am not sure what
to do next, but i would not recommend either powder coating or bead
blasting of older alloy wheels.

Regards,

Terry.
Dunedin NZ

74 GTV 2000
67 duetto

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