Maybe I will, but wherever the oxidized portions are in the coil may not be in the cut area. This homemade CFC is over 35 feet long which is likely much longer (2x?) than most CFC coils available on the market. Wherever the oxidation exists, the one thing I do know is the boiling water I recirculate through it turns light green. Let me see if I can figure out how to post a picture of this beauty… it’s @2’ in diameter!! I’ve forgotten how to attach an image… 
https://photos.google.com/photo/AF1QipMQlJIHs1nQseHa1zDCR8ZLmro1VD5tNwh0Y6–
That’s assuming corrosion isn’t throughout center section of pipe.
Can’t view image. This site is not user friendly to share images.
I believe you can’t attach an image, you have to link to it, which I see you did.
You have to set permissions to the image your trying to share.
I don’t post many pics because sometimes it works, sometimes it doesn’t
Others post pics at ease with some app. I’ve seen some trying to post pics
and give up. Perhaps others will chime in to help.
Cheers
See if this works… its a thing of beauty! 
Looks just like my garage floor did early last year, floor paint color, wear and all.
Was looking to go with epoxy, but last summer went with polyaspartic.
I’m going a completely different direction. What’s your water stats? What hops?
It looked great when I bought the house (which was unoccupied) 6 years ago, but immediately and presently sticks and pulls off onto all things rubber. There’s floor paint constantly pulling off on my kegs and tires. The house is 50 years old and obviously the garage floor wasn’t prepped properly and was painted to wow a potential buyer (me).
The recipes have been works in progress. Early batches were pretty soft Birmingham, AL water (100%) which has morphed to @ 75% distilled. Hops have been noble German / Czech and or Liberty. I used Nugget once for a bittering addition but think I over did it and am back to using low alpha nobles. I love this beer (made a pilgrimage to the brewery) and recipe and have been tweaking it over a few iterations. Tasted the original and my homebrew side by side and the recipe is pretty close. https://beerandbrewing.com/recipe-schoenramer-isch-pils/
UPDATE: Problem SOLVED!
The metallic off flavor kept getting worse and worse and was no longer subtle by any means. I dumped way too many batches… Looking back, I should have known better. I use floating dip tubes in both my 10g corny keg fermenter and serving kegs. I had bought some cheap “stainless” rings to move the pick up tube just slightly further below the beer’s surface. Turns out those little rings weren’t quality stainless and eventually the discoloration caught my eye. They were corroded and the smell from them was really strong for such a small item. I spent a lot of money on going full stainless everywhere in my brewery and was defeated by tiny $.10 POS rings. Copper was never the culprit. I should have known better than take a chance on unknown stainless.
I’m glad you found the culprit. Here’s to the next beer with no metallic taste! Cheers! [emoji482]