I have an aluminium water bottle that I'm rather fond of, I think it's possibly German army issue.
It has for some time been the water bottle in my van and as such often is left full for long periods of time. Now it seems to be building up a light coloured deposit on the inside of the aluminium.
Is this likely to be just limescale or is it something else? Should I be concerned at all? and if so how can I safely remove it?
Any answers would be appreciated.