Problem Sealing

[Monkey2674]

Ok I just got the Caswell Black dye a couble days ago. I anodize the part just fine and it comes out great, I put it in the dye and 15 min. later pull it out and it looks awesome but when I go to seal it, it turns a rust color. I have tried boiling it and steaming it. Does this dye require the caswell sealer? I have tried the dye bath at 110* and 140* still bad result. My ano tank is 72* and I anodize it till the voltage starts to drop on my CC power supply. Which is usally around 60-90min.

[Monkey2674]

I fixed the problem. I used the steam first then boil. I steamed the part for 20 min then boiled it for 10min. It came out with the rust color still on it in spots. I then took a wet papertowl and scrubed it and it came off.
The part looks great now.

[neilfj]

I can't think of any reason why this would happen unless you are not using distilled water and if you are using tap water, it is very 'hard' with a lot of minerals in it.

The symptoms match exactly. Looks great after dyeing, but you get discoloring after boiling, which would be the minerals drying on the surface. The discoloring can be removed by rubbing, which would mean it is not part of the dye solution, otherwise the discoloration would be absorbed into the surface and couldn't be wiped away. Steaming reduces the discoloration as the steam is effectively distilled water and the minerals are left behind.

Another way to tell if it is the sealing water itself is to steam the part of 30-45 minutes and DON'T boil it. You should get no mineral deposits. Steaming for 30-45 minutes is as effective as boiling (some books say it is superior).

[Monkey2674]

Thanks for the reply, I am using tap water. I will buy some more distilled water to rinse it in and then try steaming it as you suggested.

[Monkey2674]

I tried steaming it for the time you suggested and used distilled water to rinse all parts. Still came out rust color. Could it be the dye? How does sealer work? Maybe that would help.

[M_D]

It is hard to say if the problem you are experiencing is the same as ones I have seen or not, but it sounds like it may be. If you can post a good picture or two, it might help.

I’ll start by asking some questions that could help diagnose the problem.

1) What current density are you using, and are you sure of the surface area and how to calculate the required current?
2) What is the surface area?
3) What kind of power supply?
4) What acid concentration?
5) How are you prepping the part before anodizing?
6) How are you connecting the part to the current?
7) What is the starting anodizing tank temperature and ending temperature?
8 ) What temperature is the dye?
9) Did you use distilled water to mix with the dye?
10) You first said the discoloration wiped off, is it always like that, and does it wipe off easily, or does it take some effort?
11) When you are finished dying, and you rinse the part off with clean water, does it look like a brown-black, or a blue-black, or a deep dark black while it is still wet? Be sure to look at it in good light, and compare it side by side with other blacks to be sure, as a lot of tones look black until you compare it to a real black.
12) Is the whole part evenly rust colored, or are there patches or patterns that follow the shape of edges, etc.?

If the part simply wipes clean, it could still be an anodizing problem rather than a dying/sealing problem. If some of the important parameters are off, the anodize layer can be “wrong”. It could be the pore size is too large or small, and it could be the outer portion of the anodize layer is too soft and the top of it wipes off, leaving an underlying portion of it that is better. You could probably liken it too polishing old deteriorating chalky paint up to restore the proper color. If the anodize isn’t “right”, you can get rust tones (or reddish, brownish, etc.) from the black. I believe that is because some of the colors in the black are more readily held by certain pore conditions.

One possible cause is that the anodize layer is marginal because the actual current density is out of range, perhaps too low. So, you should be certain that the electrical connections are excellent. If that doesn’t help, you might try doing some tests with 15-25% more current.

I you are using tap water for your mixes, that is a possible problem. I’m sure some tap water is good enough, but a lot of it isn’t.