Sometimes there are pieces to plate with really deep recesses, and can prove very difficult to get sufficient plating in the area to allow for sanding/buffing or enough to provide protection from the environment. In the case of chrome, it would be an area that would normally receive no chrome at all due to it’s low throwing power. I talked about using robbers to avoid burning high points (http://forum.caswellplating.com/elec…r-plating.html), and allowing more plate to reach low point; here’s how to attack deep recesses…

Here’s a light housing. With normal over the edge sheet anodes only the outer surface would receive sufficient plate. The lip of the housing would be prone to burning as it’s in the high current density zone. The outer surface being a medium current density zone. The inside of the housing is shielded, so it would be low current density. By adding a robber to the area around the lip, the robber would assume the higher current density, and evens out the rest of the outer surface. However it still won’t change the inside. So, here’s the fix. In addition to your regular anodes in the tank – Cut a piece of 1/2" copper pipe a little longer than the area you want to plate/more plate. Drill a 1/8" hole in the pipe, across it. Strip back 1.5" of insulation from 12 gauge wire, long enough to reach from your +buss bar to the workpiece when it’s in the tank. Insert the end of the stripped wire to the hole drilled in the pipe. Then wrap the stripped portion tightly around the pipe. The reason I said to leave the pipe a little longer is so that there’s room to cover the wrapped wire with electrical tape. If you don’t cover the copper wire it will plate out, and eventually you’ll loose connection before all the pipe is plated out. Take the wire and wrap it around the already taped up hanger bar (rack), this will allow you to position the pipe so that it doesn’t contact the piece will in solution. On the rack, I bolted through two thin pieces of sheet metal, to act as tangs to secure the piece, and it’s negative charge. The reason that they are wrapped to is because they would act like HCD areas, and pull current away. And I’m cheap, and don’t want to expend that much more of my anodes plating onto them.
So, the piece is all rigged up, ready to get a thicker more uniform plate on the inside. Attach your negative lead to the piece, and insert into the solution. I usually secure the rack to the 1/2" bar that straddles the tank with vice grips. Take the positive wire that was wrapped and secured to the rack, and connect this to the positive buss bar.
This is where CV mode as opposed to CC is beneficial. In acid copper, I get a dense but quick plate at around 2.5 – 3 volts. When you connect the wire to the positive, set in CV mode, the amps will jump up a bit due to the close proximity of the pipe. If it were set in CC mode, the volts would drop, and you wouldn’t be plate at as well a rate. If they jump really high, then somewhere the positive charge is touching the negative. If they don’t move at all, then you’ve lost connection somewhere.
The way I test for connections is by testing for continuity. Check the tag end of the wire to the pipe for continuity, and when that’s verified, test the tag end of the wire to the rack, you don’t want continuity there.

Be creative, the pipe worked well in this case as it would be equidistant installed, be other cases may require different shapes. Just keep in mind that being equidistant is the key! Sheet anodes can be cut to shape, and if it’s a small enough area, stripped back wire can work just fine too. Wire isn’t good for baths with brighteners as it’s lacking phosphorous, so don’t make a habit of using wire.

This method only works for copper baths, for nickel and chrome you need anodes other than copper, if anyone’s interested please state so and I’ll show how to make carbon anodes. Even if not, I’ll do it anyways:)

-Jimmy

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