Electroplating Calipers help

[stubble88]

Anyone here plate their own calipers in zinc?
I’m having some issues with the calipers plating only on some areas.
Nuts and bolts plate perfectly.
I have cleaned the calipers extensively. Boiled in simple green. Dipped in muriatic acid, wire wheeled etc.
I can’t find a single thing online about this specific problem.
5 amps
Vinegar Solution
Epsom salt
4 big zinc anodes
Solution about 90 degrees
Circulating pump

[fanaudical]

I've never tried plating calipers personally, but do know a few things about electroplating (mostly for big, round, flat things where it's important to get a really even layer of something deposited). Couple of observations/questions:

Looks like your plating bath is a 5 gallon bucket and your anodes are around the sides. This probably makes a short path in a few areas and I'm guessing that you're plating closest to the anodes. Am I right?

If that's the case, you may need to increase the surface area of your anodes and and get them further away from the caliper. I think an ideal situation would be some zinc sheet formed into a surface that would be the same distance away from the caliper on all sides.

[stubble88]

That’s funny you mention that. I bought a roll of pure zinc and circled it around the perimeter inside the bucket. I got the same result. I’ve tried a couple different calipers and it attaches to the same areas, usually the edges.
Shouldn’t I have enough zinc in the solution by now to not even need anodes?
I’m calling PMB tomorrow. Looks like they also offer advice for DIYers.

[jmc1313]

Electrolysis is line of sight so may be some areas are shielded from the anode. You might try rotating the calipers so all areas are equally exposed.

[fanaudical]

+1 for PMB - My calipers went in with problems and came back perfect.