Best Masking Materials & Methods for Aluminum Anodizing

A. The picture says the coating was not completely sealed, which is not unusual with room temp fluoride seals that are a few days old.

A. Hi John,
I've got 2 things that come to mind:

-moisture
-pH

That's a natural rubber adhesive. I don't know what sort of chemical interaction it might have with the surface, but if it's a bit alkaline, you could absolutely get lightening and softening. I do not have experience with rubber adhesives applied after processing. Only silicone.

As for moisture, do you notice any difference in severity if the tape is applied within minutes vs within hours or days? This is sort of related to the pH thing in that the presence of residual moisture activates-for want of a better explanation - corrosion. The fact that it's natural rubber... disclaimer, this is not scientific as much as a hunch... it MAY be more prone to interaction with your finished surface.

Check out some different types of adhesive. Green powdercoat tape is a silicone adhesive and pretty inert! Also... Very very sticky. You may be able to achieve the same bond without substrate degradation.

Run a test panel and stick a bunch of different tapes to it, as soon as it's blown dry. Run another and do the same after a couple days drying. You'll find a good adhesive and technique for sure.

A. adv.
Please email MASKCOAT for any questions info@maskcoat.com

We have customers who use our products for electroless nickel plating on a continuing basis. We can certainly help with this.

A. One could write a book about the best masking techniques and materials and still not answer your questions. I worked in a shop that did selective hardcoat for IBM, Boeing, and others, and we usually found that each part had its own quirks and oddities. This is one area that is more art and intuition than science. We usually had a few women who did masking almost all the time (sorry guys, women did a better job than men, since they had more patience and better dexterity). These employees made more than the standard rackers, since their work required more skill.

As to who makes masking materials, there are several firms who make a living selling plugs, tapes, paints, even plastic screws for masking. Some are probably listed in the suppliers' section of this site, and "Products Finishing" now has their suppliers' Directory at their site. We used to like to visit the masking vendors' booths at the Trade Shows such as SurFin, and with just a little bit of talking, they become most willing to send samples of the masking devices which they sell, and they would also express their willingness to make custom masking if the volume warranted it. We ended up using several suppliers, because we would find one plug from one vendor, and another plug or tape from another vendor.

One trick we learned when using tape or paint, whether it was required or not, was to give the parts a light conversion coating prior to application of paint or tape. It dramatically improved the chances that the tape or paint would stick through the whole process without undercutting or even lifting off the surface, which can be a disaster, of course.

Phil Johnson
- Madison Heights, Michigan

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Ed. note: Sorry, we can't compare brands and sources on this no-registration-required site (why?). Thanks for your deft handling of the question, Phil.

A. The most common methods are tape, liquid masking (paint like) and solid masking methods like plugs.

A. Hi Tony,

Since this guy is roaming around here and he keeps tabs on my posts *GRIN*. Call Mark at U.S. Specialty Color. They sell a liquid maskant that can be purchased in 1 gallon and 5 gallon containers; I've got a 1 gallon can myself and it will probably last me a very long time, and its relatively inexpensive, around $35-40 for a 1 gal. container. If you're looking for something more along the lines of caps, plugs or tapered masks, well take your pick. There's no less than 10-12 that I can think of.

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Ed. note: Thanks, Matthew, but we don't praise or slam brands or sources in this forum (huh? why?)

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A. The best way depending on the flatness of the area is the liquid maskant. I use about 1 gallon per week for flat surfaces and it works faster and cleaner than tapes, but if you want to use tape C.S. Hyde have a green poly tape, inexpensive and can be dye cut to the right size with a release liner, we're talking pennies here for over 5K. Liquid mask is best put on by silk screen ( you can get a cheap one from a PCB supplier if they have some around and screens are also low cost.

A. There are many ways of doing masking on aluminium.

One way I can suggest is by using a special ink which is printed on the area to be masked and then a special powder is applied and it is baked till the powder and ink melt and resolidify. It can then be used to either etch or do multicolouring. The masked area covered is removed by a special solvent.

Hope this solves your problem. If not search the web for dyes for anodized aluminium.

A. Dear sir:

There are maskings which are a liquid that dries off in 24 hrs. Hope this will solve your problem.

A. Hi Tyler. Because chromic acid is highly corrosive and extremely oxidizing, I'd probably be happy that all the other sizes are holding up well. Per some chemical resistance charts I've looked at, there is no non-exotic elastomer that holds up as well -- neoprene, vinyl, and silicone all rank worse. Fluoropolymer plugs (Viton, PVDF, Teflon) would be more resistant but I don't know if they are available.

Luck & Regards,

A. Hi Tyler. You may want to establish a process you can determine the life of the plug then rotate them out based off your study. For example. Have 10 bins. New plugs go in first bin. After first use, they go in to the second bin so on and so forth. Once determined how many cycles they can go through, discard them prior to that cycle.

? How are you masking the part? Is it plugs or are you using some type of material to mask larger areas?

A We use a tape with polyester carrier and silicone adhesive. We are evaluating a different tape: polyester backing and liner with rubber adhesive (3M 8985L)