inner rim paint on Fuchs: how important is it?

[slotmeister]

I've seen a few posts debating the correct colour and type of paint for the outside (petals) and inside (i.e. back, inner circumference) of Fuchs wheels. But how important is it to have a coating of paint on the latter?
Reason I ask is that I had my front wheels off at the weekend, noticed a build-up (up to 1mm thick) of brake dust and grunge in that inner rim. Cleaned them out with water, Simple Green and a scrubbing brush. When done, I noticed that the surface colour was a washy, silvery-black; more like alloy coloured-in with a black marker pen, than an actual paint coating.
No visible etching/porosity in the surface or anything, but does it need a proper coating in there?
(I'm aware of not painting the lug-nuts area).

[porschenut]

Paint is just for looks on an aluminum wheel, so it's only as important as you decide it is.

[slotmeister]

Thanks, Dave. You've just saved me a Saturday.

[ClickClickBoom]

Originally Posted by porschenut

Paint is just for looks on an aluminum wheel, so it's only as important as you decide it is.

Wrong answer on many levels. Paint is a mechanical barrier to keep water away from the aluminum. Look up aluminum corrosion, then check out how corrosive some brake dusts are. Aluminum needs the barrier unless you are committed to continuous cleaning/polishing. Get pits on an aluminum wheel and those are stress riser points, on a relatively expensive wheel like Fuchs, ignoring the reality, can be expensive. Call one of the premium wheel refinishers, especially if yours is an all weather car, but even a car washing with standing alkaline water, (and many soaps are alkaline to a degree)could be a problem without the protection of paint.
http://corrosion-doctors.org/MatSelect/corraluminalloys.htm

[SilberUrS6]

Originally Posted by slotmeister

No visible etching/porosity in the surface or anything, but does it need a proper coating in there?
(I'm aware of not painting the lug-nuts area).

Fuchs are anodized from the factory, so they do already have a coating. Unless it has been polished away, you already have one of the most corrosion-resistant coatings on your wheels. Enjoy!

[ClickClickBoom]

Originally Posted by SilberUrS6

Fuchs are anodized from the factory, so they do already have a coating. Unless it has been polished away, you already have one of the most corrosion-resistant coatings on your wheels. Enjoy!

Rock chips, and other mechanical damages will negate that advantage, paint is easily touch up able. Brake dust can be quite corrosive, anodizing coupled with a few mils of paint is a great combo.

[porschenut]

Originally Posted by ClickClickBoom

Wrong answer on many levels. Paint is a mechanical barrier to keep water away from the aluminum. Look up aluminum corrosion, then check out how corrosive some brake dusts are. Aluminum needs the barrier unless you are committed to continuous cleaning/polishing. Get pits on an aluminum wheel and those are stress riser points, on a relatively expensive wheel like Fuchs, ignoring the reality, can be expensive. Call one of the premium wheel refinishers, especially if yours is an all weather car, but even a car washing with standing alkaline water, (and many soaps are alkaline to a degree)could be a problem without the protection of paint.
Corrosion of aluminum

Then why did the wheels come with the rims unpainted in the later years, and with both rims and petals unpainted in the early years? Those are just anodized, no paint. And, they are far more vulnerable to road damage than the interior of the barrels. Most of those wheels have been in use for about 40 years with no issues. In my opinion you're making a big deal out of nothing and ruining a guy's Saturday.

[slotmeister]

Guys, guys! I see merit in both options (paint/do nothing). As ever, am grateful for the breadth of knowledge and experience on this forum.

[ClickClickBoom]

Originally Posted by porschenut

Then why did the wheels come with the rims unpainted in the later years, and with both rims and petals unpainted in the early years? Those are just anodized, no paint. And, they are far more vulnerable to road damage than the interior of the barrels. Most of those wheels have been in use for about 40 years with no issues. In my opinion you're making a big deal out of nothing and ruining a guy's Saturday.

Take your angst to the aircraft industry. 30 years as an Airframe & Powerplant mechanic shapes my opinion. Sounds like your Saturday is the one in jeopardy, whatever. Sounds like Slot is just fine either way.