So I had several kegs to clean before I went on vacation. I let them soak overnight with an oxy clean and water solution. They are all 5 gallon corny kegs. The next day I cleaned them, emptied them out and finished rinsing them until they were sparkly clean. The problem is I had forgotten one, so after being allowed to sit in an Oxy clean solution for about two weeks. I got crystallized material stuck to the bottom and upper wall of the keg. I'm trying to figure out a way to remove these without damaging the stainless steel. Has this happened to anyone before? Any ideas or recommendations?