"Proctologically Violated©®" wrote:

wrote in message
...
On Jul 5, 11:33 am, "Proctologically Violated©®"
wrote:
Awl --

Yeah, not doing it myself, but I would like to be better prepared, to
appear
less of my normally rube-ish self, as I start the procuring process.

I'll be anodizing 1" x 12" rounds w/ tapped ends, and drilled 1/4" plate,
anywhere from 8"x36 to 12"x48, with some drilled holes.

Ito of quan, I'd proly be doing any where from 25 rounds/6 plates to mebbe
4
times that, 100 rounds/25 plates or so, at one time.

How finished does "finished" have to be, for "good" anodizing results?
For example, is typical alum round bar, extruded, and scotchbrited on a
lathe a good enough finish?

Ito "sandpaper grit" finish on plate, how coarse sandpaper is too coarse?
60? 120? 240?

How does their caustic bath act, ito softening sharp edges? Loosening
tapped holes? Should these be plugged?
I'm assuming these caustic baths will obviate any cleaning/degreasing on
my
part.

Any stories/experiences? Any sample prices?

So far, my understanding is that regular un-colored anodizing is about 1/3
the cost of colored anodizing. And that the sometimes brilliant finish you
see is not anodizing but a kind of clear-coating on top of the
anodizing --
extree charge, no doubt. And also extra protection?

And a general Q:
How does uncolored anodizing differ from regular aluminum oxidation?
Rephrased, why does un-colored anodizing look so good, and oxidized
aluminum
look so crappy? Isn't it all Al2O3?

And another general Q:

What alternatives are there to anodizing? Paint/laquer? Powder metal
coatings? Any "stains" for alum?
Any opinions on the relative merits of these, cost or otherwise?

--

Mr. PV'd


For a time, I worked Q. C. in a motor home anodizing plant. First
tank in was a hot saturated caustic etch solution, any semblance of a
polish disappeared rapidly after that. It removed any residual oxide
film, plus got rid of bending lube, finger prints and general plant
crud. So don't expect a mirror polish to last under your anodizing,
not going to happen. There's hundreds of different formulas for
anodizing processes, we were using one Alcoa developed for decorative
anodizing, which could be dyed. It used sulphuric acid for the
electrolyte. Had humongous chillers to keep the solution temp down,
too. You can have decorative anodizing, or you can go with the hard
stuff, which can't be dyed. Pick your poison. The hard stuff uses
chromic acid, EPA hates it. So probably will be limited availability
on that. The decorative sort leaves an oxide surface of hexagonal
pores, which can be filled with a dye solution and sealed off with a
hot nickel acetate solution. The color only lasts as long as the dye,
red fades fast, black fades to either blue or brown. The oxide
surface is kind of like glass, any extreme bends and the stuff
cracks. The decorative sort isn't that abrasion resistant, either, I
remember one fellow's Walther PPK was worn down to the metal with just
a couple of years of carrying.

Oxidized aluminum just happens, anodizing makes sure that the job is
done evenly.

A much more resistant sort of finish is powder coat, we had polyester
and epoxy(different colors). Either would outlast anodizing 10 to one
in the 1000 hour salt spray test. By the end, the anodized test
coupons had vanished, the powder-coated stuff was just a little chewed
around the edges.

As far as production cost is concerned, the running cost for powder
coating on a production basis is a whole lot less, a lot fewer toxics
involved. If done properly, you can recover what little powder
escapes the transfer process. We had to have folks spend a lot of
time racking and unracking parts on the anodizing side, had to use
titanium racks and hardware. Everything had to be bolted up to make
electrical contact, lots of hands involved in that. Powder-coating
parts were just hung on conveyor hooks that ran through the washer and
drying oven, a continuous process.

================================
=================================

I thought anodized alum was Da Bomb ito of finishing and durability, but
you're saying not so.

So why do people go through the extra expense of anodizing?

The aesthetics of dyed type 2 anodize are very nice. Similar results can
be achieved with the transparent powder coats I believe.


What is your opinion on the aesthetic/architectural value of anodized vs.
PMC?

Done properly, both are attractive.


I can see the trial and error/decision making on the finishing phase of this
part is going to be a long haul.

Also, the little I've read indicates that diy PMC is a lot more practical
than diy anodizing. And proly a lot more legal, as well.

DIY anodizing is very doable, been there, done that, as have a lot of
other folks. DIY powder coat is also very DIYable, I haven't done it,
but plenty of other folks have. DIY anodize requires chemical tanks, DIY
powder coat requires a big oven, so some equipment investment either
way.