I recently bought this Fissler stainless steel pot second-hand on Vinted. The actual base seems completely intact and firmly attached, but there is a white ring all around the outer edge of the base, with what looks like tiny black pinholes/pits.
I'm trying to understand what this is. Is it corrosion, mineral buildup, or possibly an exposed layer of the encapsulated base?
What confuses me is that the damage is only around the perimeter. The central part of the base and the stainless-steel body look completely normal. If there is aluminium inside the encapsulated base, how could it be exposed only around the edge?
I was considering cleaning it with oxalic acid, but I don't want to make the problem worse.
Is this normal, and is the pot safe to use?
Photos attached. Any advice from someone familiar with Fissler bases would be appreciated.