Masking for Silver Plating Inside Hollow Aluminum Cylinders

A. Hi Shreyas. I'm not totally sure that I am understanding you since, to me, 'fixtures' means 'plating racks', and plating racks usually try not to shade anything, but rather to minimize any 'rack marks'.

However, from continuous plating machines for integrated circuit lead frames (less common now in this age of surface mount components) I am familiar with the idea of rubber/vinyl 'moveable masks' which would limit precious metal plating to designated areas.

So, yes, you could build some sort of fixture that you mount the hollow cylinder on which excludes the lacquer, leaving an area lacquer-free so it can accept plating. You haven't told us the size of these aluminum cylinders yet so it is hard to visualize what the fixture would be built from and what it would look like though.

Luck & Regards,

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A. Hi. Sorry, I'm not aware of any literature specifically on masking methods and materials, but the article "Continuous Strip Plating of Electronic Components" by John Donaldson (can be purchased from sciencedirect.com) in the 1998 edition of the Metal Finishing Guidebook talks about and offers general sketches of masking techniques for continuous strip plating.

The Electroplating Engineering Handbook [on AbeBooks or eBay or Amazon affil links] and recent issues of the Metal Finishing Guidebook each have chapters on racking for electroplating.

Luck & Regards,

Hi Ted,
Thanks for the digital version of Metal Finishing Guidebook and the tip about sciencedirect.com
I appreciate all your help Sir.

A. Hi Shreyas,
1. Any specialized rack, fixture, or masking-aid will make sense only if you have an expectation for a large amount of such parts.

2. Inserting a temporary rubber/silicone mask on the plating area and dipping the whole assembly into the lacquer may not work. Reason - drying lacquer will form a layer covering part AND temporary mask, so you may have troubles to cut the lacquer layer and have a well-defined plating line (lacquer edge). So, plating solution may penetrate under a lifted lacquer's edge.

3. Depends on your Silver plating solution, some plating WAX (melted wax) may work as a masking material instead of lacquer.

Good luck.

A. Hello Shreyas!

I'm not quite clear on where exactly the intended plating is within your part, but your problem may require an approach that uses more than one type of masking, because of the risk of air pockets and restriction of plating solution circulation inside a processed piece. If it's intended to plate on one end, it's easier. If you need a band of plating within the bore, but masked at the ends, it's harder.

Look at my response on the masking for keyways thread for an idea of DIY plugs that you can try, as a background for the technique.

If you are PREVENTING plating in an internal band, you can make a single pull plug with tails. Just beware of air pocketing.

If you are actually only plating in a band, you will probably have to combine methods, including adhesives, and cured gel/lacquer types, and may find use for pull plugs.

Unfortunately masking for the lacquer application itself doesn't work so great, especially in bores where you can't use a razor, because when you go to peel off the maskant, instead of a clean edge, the lacquer can lift up or crack, or if its still soft, can leave gooey contamination.

A combination of green powdercoat tape, applied carefully and rubbed down with a dull wooden dowel for full adhesion, to hold crisp edges at the margins, plus maskant lacquer over and beyond it to cover the rest of the surface, works well.

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Ed. note: Readers are encouraged to name a source which might help Shreymas, but no testimonials please (why?)

A. Argon Masking and EPSI in the US, and Vicone in Canada are reputable. I have done business with all 3. Just be ready for a hefty fee for the initial plug mold development for custom work, and a minimum order once your design is proved out.

Thanks a lot Rachel. I really appreciate your help a lot.

A. My pleasure! I'd still recommend starting with a couple of trials making your own based on what you feel will be the best approach to your project, if only for proof-of-applicability; coming close to your goal with imperfect home-made plugs, or failing miserably but catching it before you commit to a moldmaking fee, gives you a much better starting point and will almost certainly save you a few bucks in the end when and if you bring in a plug fabrication shop.

Best of luck!