I've been working on that too. Tried scrubbing bubbles, flitz, the aluminum foil, no luck. I've been trying simple green soaks, that seems to be working. All of my green is gone, one razor had red corrosion under the green, that's coming off too. So far it seems safe, but I'm not a chemist...
My '56 Flair Tip had that on both doors. I used scrubbing bubbles, toothpaste and a paste (brand name is Twinkle) for polishing silver along with a soft toothbrush to remove it. I finally removed the corrosion but then i discovered the metal underneath had become pitted. Otherwise the razor looks good and works as it should.
I've only had mine for about 2 weeks and its get that white stuff around the head. Tried soaking it. That didn't do much. I will just need to use a toothbrush on it after every few shaves.
I had an old SS that sat in a desk drawer for years that had the green build-up on it. I gave it lots of baths, scrubbing bubbles, toothpaste/brush, etc and nothing would get rid of it all. I resorted to a brass brush. It finally got everything off, but as the plating was all gone, it does show the brass were the gunk was. It does look better than it did before.
Scrubbing bubbles always works for me. I fill a cup up with SB and let the razor soak in it. Length of time depends on how much build up there is. Soak it a while then hit it with a toothbrush. If it is still there let it soak longer. This has never failed me. Just know that when there is green gunk, the plating underneath is usually shot. Don't be surprised to lose plating in those areas when it does get clean.
I've noticed that even using a toothbrush to clean my 39C after each shave that I'm still getting a white buildup in a difficult to to place. I was wondering if I can put it through the dishwasher. I do that with my Ruger Old Army revolver!