The appearance of the wheel in the picture makes it look like it's anodized black aluminum.
If they are truly a flat or matte black paint then there's not a lot of products designed to be used on this type of coating and nothing for anodized wheels.
Tell your friend to contact the wheel manufacture and find out exactly what the black surface is, paint or anodizing.
While he has them on the phone tell him to ask them what they recommend for normal care and maintenance. Find out what the manufacture recommends because they're supposed to be the experts on their products.
If nothing else, you can probably rub them down with some type of oil-based product, even a "Trim Detailer" and this should restore a uniform, even appearance that has a dark, satin look. That is wipe on, work in and then wipe the excess off. Just a guess mind you.
This is why I always love my old school slotted mags. They are
SOLID aluminum. There's
no coating to stain or wear-off, or chip off or ever have to replace. If they oxidize it's no problem because I can easily re-polish them.
I would choose any uncoated, solid aluminum wheel with smooth surface, not machined for a wheel if for no other reason because "I" can work on them. Most wheel once something goes wrong it will be more cost effective and labor saving to simply purchase a new wheel or set of wheels.
Taking a custom wheel and trying to find a wheel shop that will undo the damage and restore to like new will end up costing about as much as simply buying new wheels.
Go for solid aluminum in the future if you have a choice...
Old School Aluminum Slotted Mag Wheels - Extreme Makeover
Before - White Rust
After - Smooth, shiny aluminum that's easy to maintain
They look good too...
Old School Slotted Mags were very popular and can usually be found on Craigslist or eBay
:xyxthumbs: