Gold Anodize on Aluminum

[Ohmite]

Here is the finish I am lookiing for:
#3 Gold Anodize to withstand 390 C
The process is:
Plate 25 min. 16% vol H2SO4 @ 15 volts
Rinse cold water
Dye Gold 5 min
Rinse cold water
5-7 min hot water
Rinse lukewarm water
Dry

The gold color comes off spotty when parts are cleaned after a month on the shelf. Cleaning was done with acetone.

What am I doing wrong?

[sswee]

Need more info.
Are you plating or anodizing?
If anodizing:
What current density are you anodizing at?
What kind of water are you rinsing with?
Are you sealing the parts at all?
Where did you get your procedure?
Is the color coming off the part or just has spots on it?

[acidrain]

Yes, more info please. Most of what you said doesn't make sense.
You said anodize, but then you mention plate.
For anodizing, 25 min at 15v makes no sense at all. We refer to the 720 rule which addresses amps per sq. ft current density x target millage = time reguired.
This forum deals with LCD which is Low Current Density of between 3 and 6 amps per sq. ft.
I usually ano for 90 minutes at 6 amps per sq. ft., and less time for gloss light colors.
Acetone is not an appropriate cleaner.
Etch, de-smut/de-ox, polish then cleaner without a lot of sitting around are the steps I take to ensure a clean, oxide-free surface.
Water rinses should be done with distilled water.
Sealing is usually done with at least boiling water or steam. Use of a ano-specific sealer of nickel-acetate solution is recommended.
Finishing off the sealing process with WD-40 works well for me.
Are we on the same page?

[Fibergeek]

Ohmite,
If you can tell us the surface area of the part you are trying to anodize, or at least its dimensions, and the current (amps) you used, we will calculate the current density for you. Once we know that we should be able to help you.

Guys,
Go easy on him. He just doesn't know yet what you know. He didn't say that he wasn't willing to learn.

[Ohmite]

Thank you all for your prompt reply and intrest. I was not trying to imply that I was "plating" or "Anodizing". I am the customer. I am new to either of these processes and am working with some very old company drawings concerning a part that I may have to scrap. It is my understanding that these were to be 'anodized' and gold in color. I have some parts from five years ago and they are great. They have a hard yello/gold finish and it does not discolor with a scrubbing of acetone. The warehouse has a lot (3000pcs) that had dust and grime on them from an aluminum casting process in the same building. Operations pulled them for use and had them "cleaned". The color is actually being removed during the cleaning. I am just the lucky guy whose job is to do a failure analysis and report back suggestions for the future.

Any other information is very welcome. My theory right now with your information is that these were not sealed properly after the coloring part of the process.

If you think otherwise let me kknow. Again thank you all very much. I will be learning more as time goes on. We are changing many things in our production processes. It looks like one thing to change is the drawing callout for the "anodizing process"

Thanks

[M_D]

It may be that the parts were improperly sealed. Anodized aluminum is also sensitive to caustics, such as TSP, Sodium Hydroxide (Lye), various acids, and etc. I don't know what they may have been exposed to while in storage, but you might look at that as a possibilty for failure in addition to the sealing process. If you have any unspoiled parts, some samples could be washed in water and resealed in a boiling (as near 212º as possible) distilled water bath for 20 minutes or so, and then tested again for color fastness. Since the dust and grime you mention may be caustic, and making them damp or wet will activate or accelerate the attack of the coating, you wouldn't want to soak them, but rather rinse the dust away and not allow it more time to attack the surface.

There are other possible reasons for the problem such as the anodize process, and the quality of dye and the dye process used.