On Aug 13, 5:42*am, (Doug Miller) wrote:
In article , "Michael Koblic" wrote:
There is something about doing the final wash in tap water: It seems to
promote oxydation. I managed to avoid it to some extent by doing the final
washes in distilled water. At least that is my personal impression. I have
not found any literature reference to this phenomenon.

Possibly due to substantial aeration of the water as it comes out of the tap,
vs. minimal aeration of distilled water being poured from a jug.

Unless you're using well water, tap water WILL have some amount of
chlorine in it, chlorine WILL attack aluminum. We had a fancy water
conditioner on both the powdercoating and anodyzing lines. Removed
the calcium and magnesium components of the hard water, too. On some
parts, they wiped them down manually with lacquer thinner before
running them through the line.

I've not had any problems with acetone contaminants and I've been
using it for a loong time for prepping parts for epoxies. If somebody
wants some super-clean stuff, pay through the nose for "reagent"
grade. I'm not a heavy user of the stuff, though, buying by the
barrel may get you something other than buying by the gallon. What I
get is "C.P." grade and usually off the shelf at the hardware store or
borg.

Re anodyzing: This is nothing magical, it produces a film of oxide
with hexagonal holes in it, really SMALL hexagonal holes. Anything
you put in the water will go in those holes, which is how they dye the
stuff. Dyed coatings get sealed afterwards, the holes are purposely
swelled shut. Now, I wouldn't want to use that particular surface to
bond to, particularly as the coating is as brittle as glass. Using
phosphoric acid for anodyzing probably etches the surface more and
phosphates the surface, might give the epoxy a bit better mechanical
grip. You might be able to produce the same surface effect with grit
blasting, though.

Stan