Some parts orange, some gold

[kco1196]

What did I do wrong? The two largest pieces turned out orange, the four smaller ones turned out golden. My first thought was to much current density (approx 12amps CD) caused dissolution. But from what I've read about dissolution the parts would have been chalky & the coating would probably 'wipe' off. Mine didn't have that.

Basically here is what I did that has always worked in the past-

degreased parts with simple green & hot water
rinsed

tumbled parts for about 3 hours w/treated corn cob media

degreased again with simple green & hot water
rinsed w/r.o. water

anodized for 65 minutes @12CD (temp was 66-69')
R.O. rinse

neutralized (baking soda & water)
R.O. rinse

dye'd in orange @120' for 15 minutes
R.O. rinse

sealed for 20 minutes in a steamy hot cooler bath was @180'
(been successful in the past)

The only thing different is my Current Density. Normally I go for 6-9 amps. All parts had excellent connection using aluminum wire. I'm speculating they weren't all the same grade aluminum.

Thanks in advance,
Gary

[acidrain]

Did you do a etch or strip step?
If you etch, and if you have mixed alloys, the 2xxx and 7xxx will come out smutty, and give you a clue that these parts should be run at 3/4 time.
I suspect that the lighter colors are 5xxx or 6xxx, and the darker colors are 2xxx or 7xxx.
Try seperating the alloys, and see if that helps.

[LOON]

Seems to be an ION.....
Had the same problem last evening.......

@ acidrain After etching some parts (feeds) they're getting black (nice look btw. ).....A clue to your theory above

P.S.: Please apologize any mistakes.....I'm from Germany....and school's out not just since summer, but 10 years....

[kco1196]

Didn't see a need to etch the parts since they weren't anodized when I got them. You think they were mixed allows? That was my first thought too. Only all 6 parts came from an old r/c car so I assumed they were all the same.

[destroyer125]

Aluminum oxidizes when its raw. an etch would give it the uniform clean finish it needs.