fingerprinting issues on anodized alum.

[legoland]

I am looking to determine how to reduce the amount of visible fingerprint appearing on an anodized sheet of aluminum with a radial brushing pattern. I have been told previously that it has something to do with my sealing process however I was looking for something a little more precise. Is there a specfic sealing solution, sealing temp and sealing time I should be using or if there is another step in the process I should be altering.

I would like to thank you all in advance for any assistance you can offer.

[destroyer125]

Wear disposible rubber latex or plastic gloves while handling parts and use a degreaser to remove all grease off the part before sticking into the tank

[legoland]

The problem is coming after the anodizing process when we are handling the parts. I do not believe this is a pre-treatment issue. I have not seen this problem on other anodized aluminum parts before but when i have seen prints they were easily wiped off.

[destroyer125]

until the parts come out of the sealer you should not handle the parts at all with your bare hands

[legoland]

These parts are on anodizing racks throughout the entire process and are not handled at all with bare hands until they are received in my office for review. Like I mentioned before, I have seen prints on other anodized aluminum part but the prints were easily removed when wiped. This is why I think it is a processing problem.

[acidrain]

What alloy, CD, tank temp, and sealing process are you currently using?
It could be desolution... is the surface chalky?
It could be lack of thorough sealing... are you steam sealing, or using the nickel acetate high temp sealer?
I use the nickel sealer at near boiling temp for 20min for .75mil, and 30min for 1mil ano thickness.

[sswee]

If the prints are under or in the anodize layer, they are happening somewhere in one of the processes before sealing. As you said, any prints after sealing will wipe off. Without seeing it first hand it is hard to make a determination as to when they might have occurred. What processes are the parts handled at all prior to them being racked? What kind of cleaning process is used after the parts are racked? Do the prints appear in the dye or on top of an even coloring?
SS

[legoland]

I have been waiting for confirmation on the chemical solutions in our pre-treatment baths however this is what i do know about our current process. Anodizing tanks are running at 90 - 95 C, We are using a Ni acetate sealing solution which varries by color our high gloss Black runs for 3 mins @ 95 C and are matte grey color runs at 4 min @ 80 C.
Some of my initial thoughts are that the texture on the aluminum is effecting the anodizing process. Our gloss black has a radial brushing pattern and our matte grey has a horizontal brushing pattern. How much do these patterns effect or alter the anodizing process? I know we have made alterations during the pre-treat to insure we do not dull the pattern from the acidic components in the pre-treatment baths.

Once again thank you

[acidrain]

Did you mean 3min and 4min per .1 ano build?

[M_D]

The brushed texture will not cause the problem you have described. I think acidrain is thinking the same thing I am, if your sealing times are 3 - 4 minutes total that is likely the problem. That is not nearly enough time, 15-30 minutes is best, depending on anodized layer thickness and etc.

When I first read this, I thought it must be a sealing problem. Parts that are not sealed or not sealed well will likely feel sticky to the touch, especially if there is any moisture present on your fingers or in the parts pores. This is not to say if the part doesn't feel sticky that it is sealed well.