I have used sankes to fermenting. I have a homemade keg washer I used to clean them with. When I first started I tried to use a flashlight and mirror to inspect them. It was hard to peer in but what I could see looked clean, so I just ran the washer and assumed they were clean. I just cut one of them open to make a second keggle. There was some nasty krausen built up in there. Now i am concerned about the cleanliness of them and have ordered a lighted inspection mirror. Photos attached of the nastiness.
I have picked up some older style bellied kegs I was planning on using as my new fermenter. Ran them through the cleaner then inspected. They looked gross. I saw streaks down the side after cleaning as opposed to a small bit of krausen. So I soaked one overnight in Oxyclean solution and still have the streaks now. I am thinking this is some kind of staining not dirt. Should I be concerned? How should I go about cleaning these or prepare them to act as a fermenter?