depth of dye color and other stuff........

[Sid03 Amateur Metal Finisher Find all posts View Profile Close Sid03]

Having an issue. Well, im having a couple issues. Let me know that ya think.


**Dye depth- Im dying batches of 2011 and 6061 the same color. I can get the 2011 to the desired color in about 4 minutes. I can leave the 6061 in the dye for 30 minutes and still not get the darkness I need. The different alloys were run in seperate batches. I tried running the 6061 both at the same time as I ran the 2011 and also for 10 minutes longer.....no noticeable difference.

Im guessing its the time in the ano bath thats doing it, although im not totally sure since letting the 6061 in longer( I seem to remember that the 6000 series takes alittle longer to ano then the 2000 series) didnt help. It LOOKED like the 6061 hit PAR much sooner then when I took it out...the voltage started dropping on my PS at about the 20 minute mark(running at 12ASF). The only other thing I was wondering is if the PH of the dye is off(ill be checking it tonight) and for some reason is more noticeable on the 6000 series.


**Small white/silver spots- Pinhead size white spots. One batch may have them out of 6 batches or so. Im guessing its the bubbles forming while anodizing not getting knocked off from my aeration. Correct?


**Black spots- Getting them on parts when using a grey dye. My dye tanks are not agitated in any form, which im guessing is the problem. Does everybody else out there actually use some sort of agitation in thier dye tanks?

[Fibergeek Metal Finishing Guru Find all posts View Profile Close Fibergeek]

I don't have a lot of time right now, so some detail will be missing, for now anyway. I'll just make some short comments.

Dye Depth.

You are seeing the voltage drop somewhat after some anodizing time, but it isn't PAR. PAR won't work if you are using titanium racking. I went into this in detail in one of he stickys (above). You probably haven't a clue at what current density the work was done at, I couldn't even guess, even if you provided current and voltage measurements. I'll bet however that its lower than you think it is. Use the 720 Rule.

4 minutes dyeing time for anything other than a pastel sounds way too short. The 2011 is probably suffering from excess dissolution (oversize pores). You will notice this in time, the coating will be mechanically weak and prone to fading. 30 minutes is a more reasonable dyeing time with the correct pore size. Your dyeing problem is with the 2011, not the 6061.

Could it just be a dye mixing/contamination problem? Maybe, you've had one before

Small white/silver spots; poor agitation is a likely cause. Could the aluminum have been bead blasted with media contaminated with iron or steel particles? These become imbedded in the aluminum, you can't remove them with anything less than aggressive sanding or surface machining.

Small black spots; poorly mixed dye (like you surmise) is likely, just stirring it regularly during dyeing works for me.

[Sid03 Amateur Metal Finisher Find all posts View Profile Close Sid03]

You probably haven't a clue at what current density the work was done at, I couldn't even guess, even if you provided current and voltage measurements. I'll bet however that its lower than you think it is. Use the 720 Rule.

yeah, youll have to elaborate. Pretty sure the 720 rule told me 38-42 minutes for a 6-7mil layer(dont have my notebook in front of me at this time). Thats what I have been going by. Maybe your right about the 2011 actually being over ano'd. Usually when that happens for me I get the chalky appearance. This looks perfectly fine. Maybe I should elaborate on the 6061.....when dying, it pretty much didnt get any more depth after 10 minutes. Truthfully, im getting scared. I keep putting time and money into this.........now to find out that even the batches that look really good may actually be over ano'd. It seems near impossible to get everything right, but I guess i'll keep trying. Im half tempted to go back to the "let r rip" method, as it seems to have given the most consistant results.

As far as the dye mixing, ive never had a problem as far as anything on my end. In speaking with the manufacturer of the dyes, I learned that pretty much no dye will be at the proper PH after mixing. If your worried about the PH, youll most likely have to adjust it every time you use the dye. In most cases it doesnt matter except for some select colors that can be a pain.

with the white dots, the parts were never blasted. Most likely the agitation, ill have to get a circulation pump to try out.


with the black dots.....im guessing your right there. Its just semi-strange that it only happens with select batches.

[M_D Amateur Metal Finisher Find all posts View Profile Close M_D]

Are the spots on the 2001 or 6061?

Again, there is the Ti racking issue, so take this only as a guide. We do most of our parts at what figures out to be 10 amps per square foot, not counting the Ti racks. In most cases, we find that 60-70 minutes works well. If the 6061 isn't dying dark enough even after 30 minutes, I would try an increase the time and see how that did. I would guess another 8-10 minutes should make quite a bit of difference.

[Fibergeek Metal Finishing Guru Find all posts View Profile Close Fibergeek]

Sid,
Take a look at the thread I started, this may explain a few things.