Some tire cleaners and other harsh chemicals will cause the paint on the recessed areas of chrome-plated aluminum wheels on 1993 DeVilles, Fleetwoods, Eldorados, Sevilles, and Allantes to soften and flake. The paint that is used on these wheels is an epoxy base paint. Although this paint is very tough, it can be affected by harsh chemicals and abrasives. The following copy is from the 1993 Cadillac Owners Manual:
Your aluminum wheels have a protective coating similar to the painted surfaces of your Cadillac. Don't use strong soaps, chemicals, chrome polish, abrasive cleaners, or abrasive cleaning brushes on them because you could damage this coating. After rinsing thoroughly, a wax may be applied.
If tire cleaner is used, make sure it does not get on the wheel surface. The effects of these cleaners may not be immediate but may show up with time.
The chrome on the wheels extends approximately 13mm (1/2 inch) into the recessed area. Do not remove the paint in the recessed area as the copper coating will show through.
The wheel should only be cleaned with a mild soap and water solution.
Please make car wash and new/used car prep personnel aware of these concerns.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.