Help... wont take dye

[xgenmods]

I am having allot of issues trying to get parts to take dye. Here is my routine...

*Part is made from 6061 t6 with a surface area of 90.72 inches^2.


1)Degrease with dawn soap (pass water break test)
2)Lye bath (3 table spoons lye to 2 gallons distilled water) for 5 min. at 60 deg.
3)Rinse with distilled water
4)De oxide / desmut dip for 10 min (part appears white) (temp is only around 70 deg but it appears to be fine at that temp)
5)Rinse with distilled water
6)Ano bath per 720 rule (CD at 6 amp, Thickness at .7 mil, so that's 3.79 amps at 84 min.) The part becomes dull. Acid temp is 60 deg
7)Rinse with distilled water
Place in grey BK dye at 140 deg for 10 min.

Dye is barely noticeable. I am using a 50 amp 30 volt CC / CV power supply.

[acidrain]

Probably lost connection. Are the racking wires aluminum? Did they take dye? What did the volts do during the run?
It looks like your math is correct, although the ano bath temp is a little low (68-70F is ideal), it shouldn't make the pores so small that dye won't penetrate.

[coopduc]

In general, parts won't take dye because they did not anodize or the ano is very thin. Assuming you area calc is correct, it appears you applied the 720 rule correctly, so the next likely culprit is the electrical connection to the parts.
Were you actually able the draw the amperage per your calc? Make sure all the connections are tight, including hangers holding the parts. Hangers should be forced into some feature on the part, not just hung on a hook. Check the sticky on the importance of good connections.
Are hangers titanium or al? If al, it it new or if previously used in anodizing, freshly stripped? With the part racked as ready to go into the acid, check for electrical continuity from the anode to the part with an ohm meter. You should have no resistance.
You also don't say much about the parts themselves. Are they newly machined from 6061 or previously anodized parts that you are re-doing? If previously anodized, it seems to me that your lye solution may not be strong enough to strip the old layer off. For stripping, use 16 oz/5 gal. If you're using it as an etch for bare 6061, it may be ok but likely not necessary. I don't think it would solve your problem, though.
Similarly, 10 min in the desmut sounds excessive, 3 min should be more than enough for even the smuttiest 2xxx parts. 6061 typically smuts very little.

[xgenmods]

Originally Posted by acidrain

Probably lost connection. Are the racking wires aluminum? Did they take dye? What did the volts do during the run?
It looks like your math is correct, although the ano bath temp is a little low (68-70F is ideal), it shouldn't make the pores so small that dye won't penetrate.

Racking wires didn't take dye well ether. Current was achieved as needed at around 19 volts. Yes this is with aluminum wires that are threaded into 1/4 20 holes about a half inch deep. I don't think they lost connection. Am I able to use stainless screws with a stainless nut to fasten the aluminum wire via tightening it in the holes? The other problem I seem to be having is that all my bead blasted parts are turning grey.

[xgenmods]

The other problem I seem to be having is that all my bead blasted parts are turning grey.

[xgenmods]

Originally Posted by coopduc

You also don't say much about the parts themselves. Are they newly machined from 6061 or previously anodized parts that you are re-doing?

Parts are newly machined fro 6061 aluminum less than 3 day old. There were deburred in a vibrating tumbler with plastic media.

[acidrain]

Beadblasted parts turning gray could mean contamination, but most likely you're over-blasting... just a quick back and forth pattern at 60psi is what I do.

Your volts seem normal considering the cool bath.
Was the dye heated to 140F? Are you able to check the PH?

[42etus]

Originally Posted by xgenmods

Am I able to use stainless screws with a stainless nut to fasten the aluminum wire via tightening it in the holes?

No, I don't think the SS screws and nuts are a good idea. I use 10-32 plastic (nylon ?) screws to attach my parts to 1/16" aluminum TIG welding wire and haven't had any failures. The plastic screws are available in 1/4-20 size.
Paul

[xgenmods]

Originally Posted by acidrain

Beadblasted parts turning gray could mean contamination, but most likely you're over-blasting... just a quick back and forth pattern at 60psi is what I do.

Your volts seem normal considering the cool bath.
Was the dye heated to 140F? Are you able to check the PH?

Yeah that could be a good chance. I did however lye dipped them and desmutted them. Beads are new so not sure if contamination on the media would be a factor or not. How exactly do you check the ph of dye? Should it be around neutral?

[acidrain]

They're all different, and it does make a difference. Use dilute battery acid or lab grade acetic acid to lower, and amonia to raise the PH. Only a couple of drops at a time, and then test with a digital meter after it's mixed and settles down.
RED BORDEAUX 6
YELLOW 4A 6
BLUE 4 A 6
VIOLET 3D 6
BLACK HBL 5.5
GREEN SCG 6.6
GOLD S 6
TURQUOISE 5.5
OLIVE DRAB 7.5
GOLDEN ORANGE 7
GREY BL 5.5
BROWN GL 6.5
TEAL 5.5
ELECTRIC BLUE 6
COPPER BF 7
FLOURESCENT PINK unk
BRONZE 5.5
DEEP RED 5.5
FLOURESCENT YELLOW 6
GREEN AEN 6
VIOLET DS 6
GREY NLN 5.5
YELLOW 3GL 6
BROWN BL 6.5
FAST BLUE 5.5
ORANGE 3A 6