17 years ago
Before I tell the story, here's a link to the results:
I was wandering thru the local hardware store when I found a bottle of
concentrated sulphuric acid, which happened to be labeled as "Drain
Cleaner"...... I chuckled a little as I thought to myself "That's not
drain cleaner, that's anodizing electrolyte" :)
Anyway, I picked up my quart of sulphuric acid, and a liquid bottle of
"RIT" black dye, inconveniently labeled as fabric dye.
Back at the house, I filled a 1 gallon plastic bucket half way with
tap water, and stuffed an aluminum baking tin down one side of the
bucket and attached it to the ground leg of my batter charger.
Next I added the electrolyte (maybe a pint) to the gallon bucket half
full of water. The decision on how much electrolyte to add was based
solely on the feeling of unrest that came as the bucket of solution
started getting REALLY warm (maybe 120F).
After that I took this little aluminum threaded web cam adapter I made
in the morning, and attached it to a piece of aluminum filler wire.
The threaded adapter and filler wire went into the ultra-sonic cleaner
for a few minutes while I went and re-read the instruction for
anodizing I found on the web.
About 10 minutes later, feeling full of confidence, I pulled the part
of the ultra-sonic cleaner and gave it a quick tap water rinse. Then
I hung the part in the still rather warm bucket of electrolyte, and
connect the positive cable of the battery charger to the aluminum wire
holding the part.
With a little trepidation, and the 12v batter charger on the 10 amp
setting, I plugged in the battery charger. Both the part and the
aluminum attached to the ground leg starting "Fizzing", and the
battery charger gauge was pegged (BTW, the battery charger lacks an
actual amp gauge, but instead has a silly gauge that instead of being
labled in amps, is labeled in percent battery charge)
At this point, I know I'm doing something, but the question is how
long should I let this run? In my research I've read conflicting
answers to this question. Some sites said 10-15 minutes for small
parts. Other sites said to let it run until the current flow pretty
much stops, as the aluminum oxide which makes the anodizing coating is
non conductive, so a fully formed coating shouldn't conduct..
Not knowing how long to let the process run, I went with the "More is
better" theory and let it run till the current dropped off and the
bubble formation was nearly non existent.
While the part was "Cooking", I went and mixed up the dye solution. I
used about 1 quart of water to half a bottle of dye. (again, staying
true to the "More is better" theory)
It took about 40 minutes for the part to "cook" completely, IE very
little current flow, and very little bubble formation. I then removed
the part, and gave it a cold water rinse. At this point the part had
a gray / green tint, and lost ALL the luster it had prior to being
After the rinse, I put the part in the dye solution, and stirred it
around a few times. About 10 minutes later I pulled it out, and it
hadn't really changed color. So I let it set for another 10 minutes,
still no color change. Having read that some alloys of aluminum need
a little heat to help the dye penetrate, I gently warmed the dye on a
hot plate, and let the part soak for about 30 minutes.
30 minutes later I pulled the part out of the now warm dye solution.
Now I had a speckled black part, but mostly it was unchanged.
Thinking that since a little heat helped, more heat should help even
more, so I turned the hot plate up.
Now I had the part sitting in a gently boiling solution of black dye,
which thankfully I had the fore thought to do out in the shop,
especially about the time the dye foamed up like boiling milk and
attempted to make a mess out of my already messy shop.
After another 30 minutes of bouncing around in the boiling dye
solution, the part pretty much looked the same as it had earlier, so I
turned the heat off, and wondered where I'd gone wrong.
As an experiment I found a scrap piece of aluminum angle laying on the
floor, and decided to try anodizing it. This time however, I decided
to only "Cook" it for 10 minutes. Amazingly this scrap piece came out
nearly perfect, as seen in the pictures!
So the question is, why did my threaded web cam adapter fail?
Here' my current thinking, which I hope to explore tomorrow after
cleaning the part up on the lathe.
#1 The electrolyte solution was rather warm when I hung the part in
it. perhaps the warm electrolyte was sealing the part as the anodizing
coating was being made. By the time I tried coating the scrap piece
of angle, the electrolyte solution was nearly room temperature.
#2 I "Cooked" the part too long. 40 minutes may have been WAY too
much, and perhaps caused most of the pores in the anodizing layer to
become too small to accept the cheap dye I used.
#3 The unknown alloy I used to fabricate the threaded part may not
like the anodizing process, or the selection of dye I used.
#4 Some combination of the above.
BTW, the wire brush marks near the threads on the web-cam adapter were
done after the part had been boiling in the dye for 30 minutes. For
some reason the dye sort of "Chunked up" on the sides with the
threads. I couldn't wipe the chunks of dye off, so I tried it with
the wire brush, which knocked the big stuff off...
BTW #2, I hope and pray that I can make the web cam adapter look as
good as that stupid piece of scrap I did, because I'm amazed how well
that piece of scrap turned out!
BTW #3, as an experiment, I tossed a piece of the same scrap angle
into the dye, without "Cooking" it first, and the dye just wiped off
In any event, It was a pretty good way to spend a day off :)
(My telescope construction, Testing, and Coating site)
Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent.