EMRFD Message Archive 6113

Message Date From Subject
6113 2011-04-13 17:05:33 joe Cleaning Coils
I have some old B/W coils that have been in storage for some time and are corroded. Any good ways to clean them? I plan to use them for a homebrew antenna tuner.

Joe W3GW
6131 2011-04-14 20:52:48 David Re: Cleaning Coils
I too have a gold mine or should I say a silver mine of roller L's, Large caps and coils that have seen better days.

2 approaches to the problem.

1) Aluminum foil silver cleaning method. Line Aluminum foil in the bottom of a container then add a warm dissolved salt/baking soda mixture. When the parts touch the Al it "wants" the sulfur from the silver sulfide more than the silver and voila! I don't know about a copper sulfide reaction but it works for silver corrosion.

2) If the first approach doesn't work I'd try what I do for rusted metal. Mix up some Arm and Hammer washing soda in a bucket and attach the part to the Neg termial of a car batter charger and the Pos terminal to a sacrificial anode. I've taken rusted ir
6138 2011-04-15 19:37:33 David Re: Cleaning Coils and noodle time
I needed to rebuild a salvaged Kay Attenuator today which was either tin or silver coated inside. The coating was blotchy and dark grey in places so this was a perfect opportunity to try the Aluminum sheet solution.

Aside from having to replace the cooked resistors and rebuild the nice custom Kay switches because contact cleaners didn't work by shooting it in and around the toggle. 100% alcohol did work in the end when I took several apart and found green stuff blocking the brass roller from mating with the switch contacts. I did have 3-48 screws to replace the long rivets that held the switch plate on.

Anyway, after obtaining a glass loaf pan, I cooked up some salt and baking soda solution (note the fizzing action that goes on). Lining the loaf pan with foil and pouring the hot solution in I expected the inside of the attenuator to instantly turn a bright finish like I had seen done with real silverwear. No, notta, nothing happened...

Ok, then I tried Tarnx and Silvo followed by acetone, alcohol, beer....

Nothing worked. The BNC connectors certainly were much brighter but not the inside. This left me with several options, the inside is tin in which case I need to check on the chemical reaction that will work or the silver coating was kinda dodgy in the first place or the Al sheet method doesn't work (unlikely as I've used it work on real silverware).

I also had a Roller L handy that was made before I was born and coil was almost black. It didn't turn bright instantly but after a minute or two I could see shiny metal. After 5 minutes and rinsing and wiping it off I now have a coil that looks brand new! The copper roller piece didn't improve however.

So the the Al sheet solution works on some metals but not on copper or tin.

Its noodle time.

6140 2011-04-16 08:58:26 David Re: Cleaning Coils part deux
Tin oxide seems to be terrible stuff. The literature suggests hydrocloric acid or its close cousin muriaic acid as a chemical cleaning agent. I elected to try my second solution first.

I mixed Arm and Hammer washing soda with water in the glass loaf pan and connected the neg terminal of my battery charger to the attenuator body and a copper wire as a pos anode. After about 1/2 hour the tin oxide coating was cleaner but not as shining compared to the first method I used. The big problem was the elecrolytic action started to remove the paint/powdercoating off the attenuator body. I stopped cleaning the attenuator at this point and put it back together.

I did take another ancient coil form and threw it in to see what would happen. After 15 minutes I washed and rinsed it off. Wow brand new!

Anything copper plated will be stripped using this method so don't use it on copper. My batter charger clamps are completely void of copper plating now.

The first method using Al foil is effective on silver and less so on tin but not as aggressive as the second solutin using electrolytic dipping. Both methods work well