marks on stainless steel tanks

Only add clean water to the milk.

Anny idea what is causing the marks?

My first remark is from a standard joke:

Health inspector to worker : I hear you are adding dirty water to the milk.

Reply : No sir only clean water.

heres how to help us help you- describe the problem!'

are the black mark on inside surface or outside surface of tank?

horizontal and continuous around the tank, or vertical and randomly dispersed?

wide like a scuff or narrower than a ball point pen mark?

seem to be associated with fluid level, or an area on the bottom?

what type off stainless? what process is performed in it?what is your cleaning procedure, including cleaner name?

problem solving is only difficult.

remote viewing and mind reading nearly impossible.

love to help, give us something to work with.

milo

Is it related to any welded area? Or near any structural element? Or near any different material connection?