Masking Chromic Anodising

[chrisamey]

Hi

We chromic anodise an aluminium alloy cast component to MIL-A-8625 Type I Class 1. There are certain areas on this components that need to be electrical conductive, therefore we strip the anodise (using glass bead blast) and chemical film to MIL-C-5541 Class 3. This is a very long and expensive process, ideally we would like to be able to mask the areas during the initial anodising process, which would therefore remove the need for blasting.

I have been unable to find a suitable masking solution, none of the brush applied solutions are compatible with chromic anodising (due to high temp and solution).

Does anyone know of any tapes or solutions that can easily be applied and removed and that are suitable for chromic anodising? The masked areas do not need to very clean cut – we can live with a bit of leaking under the mask.

Some of the areas to be masked are flat surfaces and some are diameters.

Thank you for any help that people can supply.

Chris

 

[magic612]

Chris -

I admit I am not familiar enough with all of the specifics of anodizing to know exactly what chromic anodizing involves as far as heat and chemicals. However, my company does provide masking tape to a lot of anodizers, and I'd bet that at least a few of them are doing chromic anodizing.

I know that the following kinds of tapes have been used successfully in anodizing situations:

Lead tape (rubber adhesive)
Aluminum tape (acrylic adhesive)
Polyester tape (silicone adhesive)
Crepe tape (acrylic adhesive)

Since you mentioned high temp, I'm not sure the lead tape would be appropriate. And not being familiar with chromic anodizing and the specific chemicals involved, I would suggest the polyester tape with silicone adhesive first (as it would have the best chemical resistance), then the other options if that did not work well, as acrylic adhesives very often are more aggressive (sticky) than silicone.

 

[chrisamey]

Thanks for your reply. The temperature that chromic anodising is performed is not actually that high only about 40C it is this with the combination of the chromic acid that is normally the problem. Although some of the sealing and washing procedures can be up at around 90-100C this is normally done is less aggressive solutions.

Thank you very much for your help - I hope it works.

Regards

Chris

 

[chrisamey]

Hi

I was wondering if you could send me further details about the tape that you have recommended and maybe a URL to your companies website so that I can get further details.

Our company website is

http://www.porvairfiltration.com/microfiltrex.html

Thanks

Chris

 

[magic612]

Hi Chris -

We have more information at our website -

http://www.viadon.com

- and although there is not a specific "anodizing" link (this is due to the variety of tapes which can be used for it), check out the "Tapes - Lead foil", "Tapes - Aluminum foil", "Tapes for Powder Coating" and "Tapes - High Temperature Crepe" links.

If you need further information from there, feel free to contact us. Hope that helps.

Dave