Removing sharp perforation edges on stators with ferric chloride

[Audio_idiot]

Hi,

Is this the electro polishing we are talkng about now??

http://www3.telus.net/public/aschoep...lyticrust.html

Cheers

[bear]

Originally posted by glorocks

The panel should be first wet sanded with 4-600 grit "wet or dry" emory paper. Use a soft rubber sanding block. This may be enough to knock down the ridges.

<edit>

That would not be emory paper.
Either SiC, silicon carbide, or else aluminum oxide if it is wet or dry.

_-_-bear

[glorocks]

Bear, you're right. Back in my day, we called wet sanding SiC abrasive papers "emory" paper. I'll be more careful in the future.

[glorocks]

Regardless of what we call the abrasive, the important point is to use liberal amounts of water to keep the abrasive from clogging up. A soft backing for the abrasive system, such as a heavy sponge or a soft grout float will allow you to break down the edges without the use of chemicals.

[auplater]

Using NaOH (lye) will usually leave a grey or black smut on the aluminum... it will etch but not polish the edges... maybe not the effect you want...

Commercial epolish uses decidedly unfriendly acids and high current density for the desired effect... typically Sulfuric/HF solutions ... or phosphoric-chromic-sulfuric-nitric mixes at 100 - 200 asf... not gonna post any formulas as someone will get hurt...

Brite dipping would also work... but again... find an anodizer and let them deal with the hazards...

Lye won't form an oxide, it'll keep etching till all the OH is exhausted and will leave the aforementioned smut.

Best to either find a commercial plating/finishing shop and see if they'll do it... or live with a crappy half-baked NaOH etch and then sand the results... <- would not be my choice.

Why not pour lye down the drain? That's what Drano is... and most other drain cleaners (excepting the sulfuric acid or enzyme types)... won't hurt pvc or copper plumbing... and it'll clean out all the hair and organic crud from years of mis-use...

btw... emery IS aluminum oxide.... http://en.wikipedia.org/wiki/Emery_(mineral)

Emory is a university in Atlanta Ga.

I'd leave the chemistry to chemists..

John L

[bigwill]

Yeah, I'm now thinking of just countersinking every hole and sanding it with very fine whatever-paper.

However, I performed an experiment in which I dipped an aluminium candle holder in lye. The black smut readily washes off and the resulting surface does not look corroded.. In fact it looks pretty good.

[auplater]

If it works, and gives you what you want.. go for it...

The smut problem depends on the alloy... low alloy Al (6061, 2000 series) aren't too big of a problem, especially if you can wipe the smut off and no further finishing is required. You can also polish up the surface afterwards with Softscrub (w/o the bleach) or even Ajax or Comet.. (or a pumice slurry)

John L.

[bigwill]

Isn't Al just Al? What is it alloyed with?

[auplater]

Originally posted by bigwill
Isn't Al just Al? What is it alloyed with?

Not at all... pure aluminum is almost never found... most is 6061, alloyed with copper, silicon, and magnesium to make it heat treatable...

http://www.suppliersonline.com/prope.../6061.asp#Spec

other alloys include 202x copper-magnesium series, 7xxx series, etc... pure Al is extremely soft and of limited use... I believe spec'd 1199... 1000 series is the purest

http://mdmetric.com/tech/alumcomp.htm

All these alloys behave very differentluy and have dramatic differences in tensile stregth, heat treatability, surface properties, etc.

most of the black smut left is copper, iron, silicon and other insoluble crud... it plays havoc in the metal finishing industry w/o the proper post treatments (hence the nitric, HF, etc. ) post-etch rinses

FWIW

John L.

[bear]

Auplater knows his stuff in this department.

Although I have never seen a "smut" build up on aluminum, that doesn't mean that it wouldn't happen.

As far as pouring lye down the drain, it could simply etch right through copper or brass sink traps. Probably wouldn't, and just leave it bright and shiny?

Guess it depends somewhat on the amount and concentration...

Ok, flush liberally with water when ur done...



_-_-bear