Black turns bronzy black

[blurrycustoms]

Just wondering if anyone else is having the same problem. I'm trying to use dye this part black, but it's coming out more of a dark bronze-black. I've got to run, but I'll try and post more a little later as far as my set up goes, but I just wanted to know if anyone has had the same problem.

[blurrycustoms]

Alright,

I'm running about 12% sulfuric acid. My part is 82.6 sq. in. Running about 2 amps @12 volts. My calculations have me at 216 minutes. So I am thinking I should up the acid concentration which would increase the current draw and decrease my time.

But I am thinking that I may not be getting the dye sealed fast enough. I am dying in a cold bath about 80 F up to 30 minutes. And then sealing for about 25 minutes at 190 F. Sealant turns pretty dark so I am losing a lot of dye.

What do ya' think, should I heat up my dye bath?

[Z]

sounds like your parts could be bleeding into your seal tank. Check your PH of both the sealer tank and dye tank. If the sealer tank PH is off it causes bleeding. A lot of dyes can run just fine at ambient temperature but I'd try to elevate the temp up to 140 F. As for getting the part sealed quick enough that isn't the problem parts can hang around for hours without being sealed.

12% is a little low in concentration.. ideal is 15-17% by weight.

[acidrain]

Sounds like your current density is a little low, and could be causing desolution (acid eats the ano film as it's being built).
I'm guessing that your using the let-r-fly method... not a very accurate way of anodizing.
If you're using a 12v battery charger, you should consider a CC/CV power source. 12v is going to give you grief, especially hard to dye colors like black and red.
Also, why aren't you heating the dye? Could be the problem right there, except that you said the dye is leaching into the sealer, which leads be to believe the pores have been eaten too big from desolution. Are you using anodizing dye?
Even if you up your acid concentration, you will be limited by your power source (assuming it's a 12v power source).

[blurrycustoms]

Originally Posted by acidrain

Sounds like your current density is a little low, and could be causing desolution (acid eats the ano film as it's being built).
I'm guessing that your using the let-r-fly method... not a very accurate way of anodizing.
If you're using a 12v battery charger, you should consider a CC/CV power source. 12v is going to give you grief, especially hard to dye colors like black and red.
Also, why aren't you heating the dye? Could be the problem right there, except that you said the dye is leaching into the sealer, which leads be to believe the pores have been eaten too big from desolution. Are you using anodizing dye?
Even if you up your acid concentration, you will be limited by your power source (assuming it's a 12v power source).

Alright, so another failed attempt today. I used heated dye. I anodized the piece for 180 minutes it was drawing 2 amps the entire time from a manual 12v charger. (That's all I have at the moment so I am trying to make it work the best I can. I'll look for a cc/cv ps in the near future.) Sat in 140 F dye for 30 minutes and stuck it in the sealer for 30 minutes. Not as much leaching, but I still get that sharpie marker black look. According to the 720 rule I am running just under 3.5 amp current density.

So it has to be dissolution. What would be the best way to remedy that with my current situation? Lower acid concentration? Colder/warmer acid bath? Shorter anodize time? Bigger cathode? I'm kind of lost at this point. At least I'm getting consistent results!

[blurrycustoms]

Oh and I did up my acid concentration to about 18%

[acidrain]

3.5 amps per sq. ft. is too low... I wouldn't go any lower than a 4.5A/sq.ft. CD. 6 is perfect for home ano in my opinion.
18% by volume (battery acid:distilled water)? That is still a bit low... you want 25% (1:3 by volume). Making the acid stronger will make it easier for the current to flow... for the same amount of amps, the volts will be lower, therefor, if you are limited to 12v, the amps will be higher (higher current density). Same with acid bath temperature. Lower temp is harder for current to pass. You should try to get your acid bath to 68F-70F (no higher than 70F, or desolution will occur).
If your temp is low, try 68F first (use a digital thermometer... ~$10 at Harbor Freight).
If that still doesn't get you to at least 4.5 CD, increase your acid to 25%.
Remember, only change one thing at a time when doing controlled experiments. I would definately start with the temp... it ALWAYS has to be 68F-70F.
Oh, and you didn't say... are you using Caswell's dye?

[blurrycustoms]

Originally Posted by acidrain

3.5 amps per sq. ft. is too low... I wouldn't go any lower than a 4.5A/sq.ft. CD. 6 is perfect for home ano in my opinion.
18% by volume (battery acid:distilled water)? That is still a bit low... you want 25% (1:3 by volume). Making the acid stronger will make it easier for the current to flow... for the same amount of amps, the volts will be lower, therefor, if you are limited to 12v, the amps will be higher (higher current density). Same with acid bath temperature. Lower temp is harder for current to pass. You should try to get your acid bath to 68F-70F (no higher than 70F, or desolution will occur).
If your temp is low, try 68F first (use a digital thermometer... ~$10 at Harbor Freight).
If that still doesn't get you to at least 4.5 CD, increase your acid to 25%.
Remember, only change one thing at a time when doing controlled experiments. I would definately start with the temp... it ALWAYS has to be 68F-70F.
Oh, and you didn't say... are you using Caswell's dye?

Yeah, I'm using Black HBL. I'll give this a go again tomorrow. If anyone here wants a job for their home anodizing set up I may have some work for you! I'm kidding and serious at the same time. Shoot me a pm!

[blackcote]

Originally Posted by acidrain

it ALWAYS has to be 68F-70F.

acidrain ALWAYS gives excellent advice, but this statement I have to disagree with. your ideal temp depends on a number of factors from my experience. Right now we're running 70-72 degrees at 6ASF and having no problems, in fact if we go down to 68-70 we start having dye absorbtion problems (I assume becuase pore size is too small, but that's just a guess) It sounds that if your losing dye in the sealer your pore size is definately too big. So lowering the ano temp should help. Definately heat the dye up. it helps get it down into the pores it seems. If you still decide to send it out to get done, you have a pm.

[acidrain]

Originally Posted by blackcote

acidrain ALWAYS gives excellent advice, but this statement I have to disagree with. your ideal temp depends on a number of factors from my experience. Right now we're running 70-72 degrees at 6ASF and having no problems, in fact if we go down to 68-70 we start having dye absorbtion problems (I assume becuase pore size is too small, but that's just a guess) It sounds that if your losing dye in the sealer your pore size is definately too big. So lowering the ano temp should help. Definately heat the dye up. it helps get it down into the pores it seems. If you still decide to send it out to get done, you have a pm.

I always appreciate the opinions of my highly respected colleagues.
Could be the difference in our thermometers. I have several of the cheap Harbor Freight thermos... they all seem to read differently .