Gold plating of wave guides

First, what type of waveguide/cavity material? I'll assume Copper although Aluminum is also possible as well as ferrous based (you did say you were in an edu).  

The next issue is that of the matte brown finish. Sounds like you're burning the plate. I suggest a Hull cell analysis. Essentially, you plate up on a brass shim that is placed at an angle to the anode. This allows you to compare varying current density to plated appearance.

I am also assuming that you are using an appropriate anode w/ appropriate surface area. A platinum coated anode works best although stainless steel can be used for short periods of time without damaging the bath. The surface area of the anode to cathode should be about 1:1 although 2:1 will be ok.  

Good luck, Jeff

Antenna Engineering Handbook

Hi Alex,

Most professionals buy proprietary gold plating solutions rather than trying to make them from scratch according to old formulas. That way you get the most modern approaches, and you get the supplier's expertise and lab working for you. That's perhaps what you might want to try. Gold Touch and Technicspecialize in this.

Jeff,

As you probably know, many wave guides are electroformed because it's such a great way to build complicated hollow shapes. Suppose Alex were to polish an aluminum or wax mandrel, then electroplate it with gold, then back it up and give it integrity by electroforming with copper or nickel, then dissolve away the aluminum or wax. He'd have a copper or nickel waveguide with a highly polished gold surface. From your experience do you see any reason this wouldn't be feasible? Thanks.

Vijay,

Thanks for the feedback. But wave guides often are electroformed, and it's a good application for gold electroplating. The third advantage you listed for sputtering is true, i.e., that it's easier to get coatings of uniform thickness with sputtering than plating, but the other two purported advantages may not be. In many cases electroplating yields 'perfect adhesion', which means that it is impossible to separate the materials at the boundary -- either the coating or the substrate will rip instead. Plus, this application doesn't sound line-of-sight where sputtering would work; it sounds like Alex wants to plate the cavity (interior) of a waveguide, not the outside of it.