Better racks/jigs to reduce plating defects

A. Hi Glenn. Production platers usually use custom-designed plastisol coated plating racks, usually made mostly of copper, but often with stainless steel spring clips or tips ... reserving 'wiring' for special situations.

There is a good chapter on the subject in the old but reliable Electroplating Engineering Handbook.

When parts are wired, copper wire is usually used because it's conductivity is 15X to 25X the conductivity of stainless steel. And aluminum wire is not much used because unreliable contact can be a problem, and it's not resistant to the strong caustics that are part of most plating cycles.

Electricians generally consider 14 gauge copper wire good for 15 Amp circuits, and 12 gauge good for 20 Amps. That's probably a rather conservative estimate for this application, but it should give you a starting point.

Luck & Regards,

A. You can use Teflon coated hangers for hand tools. It is definitely helpful to avoid chrome yellow mark.

A. Any place that the jig touches is going to leave a mark so the whole idea is to have the contact point as small as possible and still carry the load. The next way is to insulate the jig to as close as possible to the actual contact point that it does not serve as a robber or thief. It can not be so large that it shields the part or you will get very thin or no plate. Professional jig makers will use copper to carry the main load and plastisol coat it so that it does not plate. Smaller coated copper will be used to carry the feeder loads and finally very short spring clip attachments might be made of stainless steel with these using a very thin insulator coating.

The best method is to make the contact point where it will not show when the tool is assembled. The rack (jig) may be a lot harder to build, but it will save a lot of grief.

A. Hi, Sanjay.

This happens because the chrome plating is attracted to, and deposits onto, the wire. Chrome has terribly low throwing power. The previous answers tell the sad story that you can't solve this problem of poor racking by altering the solution chemistry, only by correcting the poor racking so there are no wires on the significant surfaces. If you use racks, be sure to insulate the ends of the hooks, removing insulation only where absolutely necessary for contact. Good luck.

Regards,

A. Bojan, sorry to know of your difficulty. This is a very common concern and there are no easy answers. Two solutions that I have used in the past: 1. Rack the parts "loosely" so that they can move a bit but not too much to cause damage. The rack tips may need to be dulled or adjusted to allow for this. 2. Process the given items "halfway" or so then pull the parts out, adjust the positioning on the rack so that the parts are moved from their original positions and then continue. Obviously, #2 is not a preferred solution but it can be quite effective.

A. Hi Varun. Generally, plating shops do not do plastisol coating of their racks. This is a service generally done by rack manufacturers and plating equipment suppliers. I worked at a plating equipment manufacturer who did it, but never did it personally so I don't know all the fine details -- but it was generally as follows:
All loose plastisol that could be removed was cut off with box cutters, etc., and pulled off. What was too adherent would be burned off in an oven. Then the component would be solvent cleaned, then a primer / adhesion promoter was brushed on, then the component was dipped in a vat full of plastisol, then it was baked.

I'm sure there are rack manufacturers and equipment suppliers who can offer he service to you. Touch-up can be done with air-dry plastisol formulations but it is not nearly as satisfactory as bake-cured.

Luck & Regards,