I'm using a Tescoma paloma moka pot (aluminium) and after three years (and one mistake made by a friend of mine - tried to clean it with detergent) I noticed a build-up of two things:
White spots that looks like oxidization (also they disappeared after brewing water with lemon)
that they are not removed after brewing or washing with water.
I read the other similar questions but I'm not able to guess if this is oxidization or something that I should be afraid of. What is your opinion on that?