Update Dec. 3, 2009
(Links to webpages no longer available have been removed)
Very difficult to remove anodize from bumper surface, starting
with 220 grit wet/dry silicon carbide paper and two different pad type sanders, to get the anodize off and get down to the
aluminum. Make sure that you are using a straight line sander when you get to the aluminum, to do all your resurfacing
work. Don't use an orbital sander at this point! Discussion with several owners of other model year E28's (1987 and 1988)
makes me suspect that the anodize applied in 1982 production was much thicker than applied to later models. These exhibit
anodize removal simply by using a steel wool pad, after applying some oven clearner.
Hmmm, oven cleaner and even a solution using 100% lye didn't
touch my bumper anodize! Perhaps an anodize was not used on later production, but something like a clear coat finish? That
would explain the easier removal process involving steel wool and household cleaners on some E28 bumpers. These chemicals
had absolutely no effect on my bumper.
On this rear bumper, I have had to use a draw file technique
to cut through the anodize enough to allow the silicon carbide to be able get a hold on the surface for removal. I've got
to find a better way to deal with this, before I attempt to polish the front bumper.
The other thing I suggest you do, while everything is apart,
is to open up the bolt holes in the rubber trim cover so that they are slots and have an additional 1/4-inch horizontal play
at both ends, using a suitable grinder bit. When you remount the trim cover, do not tighten down the bolts, but make them
just snug so that the trim piece can move in the slots you made as it expands and contracts from temperature changes. This
will keep it from rippling and becoming wavy. Lastly, here are some useful links about this subject:
