what have you wrecked

[cooldad]

I thought we could try somthing here. I was wondering how bad you could screw up a part by anodizing, incorrectly. Fibergeek already told me of part of a gun he destroyed, but not from anodizing. So I was thinking that hearing what kind of different things can go wrong would give me a better feel for what I can expect. We all make mistakes so there should be lots unless this system is pretty foolproof.

Later,
Cooldad

[Fibergeek]

I don't think you understand.

I can't think of any mechanism in anodizing that could do any more damage to a part than pitting it. Pitting is caused by a gross overcurrent condition, usually brought on by no current limiting. It's not like you can dissolve it or melt it or anything like that.
"Screwed up" in anodizing means lousy coating thickness/uniformity/pore structure, which will manifest itself by poor dyeing results. Stripping it off so that you can redo it is the dangerous part of the operation, and is where damage usually occurs.

A mixture of concentrated nitric and chromic (or is it phosphoric?) acids can dissolve the anodize without attacking the bare aluminum. But this nasty concoction is so hazardous to the operator, it is a case of the cure being worse than the disease.

[cooldad]

You were right, I was thinking that there would also be problems like distortion of shape and size. For example if I were to do a cylinder or head from a bike engine. I was worried that I could mess up the bore size of the cylinder or the flatness of the head. Another one was fork tubes, they are very fussy on i.d. specs. Even though I dont want the inside anodized I was worried I could still "screw up" the working surface on the inside of the tube. These are the kind of things I was wondering about. So if that doesnt happen Im feeling more confident already.

[NeoMoses]

Like FiberGeek said, the only process that will really 'scrap' a part is the stripping process, assuming you're using standard anodizing or the LCD method.

I have tried to measure the thickness of an anodized layer, as I have heard that it does change the dimensions slightly. However, I do not have the measurement tools necessary. I have never seen a change that was measureable with a pair of calipers good to 0.001". I would imagine that if your tolerances are +/-0.001" or larger, you will have no problems.

Also, there are ways to mask areas that you do not wish to be anodized.

Hope it helps!

[Tim Wiltse]

Yup... stripping old anodizing is what will get you. I have ruined a $150 model airplane engine from the 50's using anodizing stripper!


Later,
Tim

[cooldad]

What happens? I detect that maybe this is where you can get distortion. Or does this just destroy the cosmetic value of you piece?

[Fibergeek]

Tim, please field this question.
Thanks.
Fibergeek

[Tim Wiltse]

Well what happened was it started to remove the anodize coating on certain places right off the bat but other spots took forever. By the time all the anodizing was off the first places it was removed from were really pitted and the i.d. on a couple of places were so bad it was junk!!


Later,
Tim

[cooldad]

Sorry guys Im not meaning to frustrate anyone, I understand what is being said here. I read from all of you though that stripping can destroy your pieces, so I was just curios about what damages can occur during this process. Like what was said about anodizing, the pitting being a screw up.

I guess other than that Ill just save posting for when I start anodizing, and if I run into problems.