Eric R Snow wrote:

I bought this stuff because Grant and others said it worked well to
remove oils. And it sure does. I suspected that it might be pretty
strongly alkaline because of the soapy feel. And I got proof when
washing some anodized parts that came in for mods. The Castrol purple
stuff started to remove the dye (black) and on the machined surfaces
started to dull them slightly. I will still use the stuff on aluminum
if I need to but will not let it sit for long. I wonder if it would
make a good weld prep for aluminum?
ERS

I use the purple degreaser myself, in fact I have a 5 gal of it. It is
one of the few chemicals in my (home) shop that I use gloves when using.
It is very strongly alkaline (lye) and will do a number on your hands
just like cement will.

Pete C.