Was it blued or nickel finish?
The combination of the caustic nature of navel jelly and time/moisture exposure may necessitate and complete rework, and refinish.
Another thing to try, brass wool and brake fluid, brass is alot softer than the metal, wont alter it, brake fluid acts as a cleaner/lube to help break stuff loose. I use brass wool and brake fluid to remove rust and such on parts, it won't wear bluing or metal finishes.