parts not stripping right

[mkriegs]

I have this set of 5 parts of mine that I've been putting off anodizing for about 2 months now and they've just been neglected in my garage for the whole time. I thought they had an anno coat on them the whole time they were sitting there but now that I think of it theres a good chance that they were as raw aluminum.

anyways, whenever I strip these parts there are a few random splotches that look like raw aluminum is supposed to look but most of the part is just a bright white. so I've tried to anno these parts twice now and both times they had the exact same raw spots on them after stripping and both times those raw spots were the only spots to take dye (although the parts that did take dye look AMAZING thanks to my new Mastech unit), also the spots that did take dye stripped just right so I don't think it's the stripper.

I'm currently using lye as my stripper, I know I should be using caswell stripper, but I just bought a $200 rectifier and some other supplies from caswell so can't afford to pay $50+ for something that I have a substitute for in the meantime.

Any help is greatly appreciated, hopefully one day I'll even be able to return the favor

[sswee]

What finish do the parts have?
how long did it take to strip the ano off to rerun and how long have you stripped them for, total time?
SS

[acidrain]

I've had some parts that look as you've described. Sometimes parts have a wierd alloy or grain that just won't ano well.
All I can suggest is to strip, desmut, etch, desmut and then buff or beadblast. If it continues, there is probably something in the aluminum part.

[mkriegs]

sswee - the parts have a sort of flat/dust finish if that's what you meant, and it took the anno less than 10 minutes to come off but I've left the parts in the stripper for as long as 25 minutes and this mystery coating is still on.

acidrain - I'll try that.

[sswee]

I have nothing to add that acidrain did not cover.
SS

[erckgillis]

Try the Zincate...

[acidrain]

Originally Posted by erckgillis

Try the Zincate...

Huh? For anodizing?
I may be way off on this, but zinc, plus sulfuric acid = a fizzing, bubbling mess.

[sswee]

You're not way off acidrain.
SS