Tim Shoppa wrote:
I've got an aluminum panel (front of a very fancy instrument) that I
want to re-paint. Current paint is pretty shabby, but then again it's
from 40 years ago. I'm sure I can get the old paint off (between
strippers and sanding) but what's the next step?

What's a good pre-painting etch for aluminum? I've used
phosphate-based etches before but something tells me that this isn't
the best thing for aluminum.

And after the etch, I'm probably limited to cans of spray paint.
Although going to an automotive paint shop and asking them to load a
paint can for me is a possibility, I don't walk in without a clue as to
what I want to buy. OTOH if I can buy it off the shelf then that's
great too.

I can bake the panel after painting, in my past experience (with
discount-store brands of spray paint) this makes a big difference in
durability.
I've got some stuff I bought 20 years ago, and you probably can't get
exactly that stuff anymore. There is a 2-part concoction that seems
to be a mixture of contact cement and Zinc Chromate. It has a totally
noxious solvent odor. And, I know about the cement part because I
always get it on my hands, and it peels off just like contact cement.

I sand the aluminum with 240 grit wet or dri sandpaper, but do it wet
to prolong the life of the sandpaper. I then wash with water, and then
wipe down with rubbing alcohol.

The label on the primer reads "zinc chromate wash primer". The zinc
chromate is an anti-corrosion treatment, and probably isn't necessary
in my use.

After the primer, I use a "baking enamel" that is only slightly less
noxious smelling than the primer. I let the parts dry for a day
or so, and then sometimes pre-heat them with a heat gun while still
in the fume hood to drive off the last of the solvents before a
200 F bake in the kitchen oven.

This produces a pretty tough coating, but it is not as rugged as a good
appliance finish.

Jon