"mm" wrote in message
...
How long before cold or room temperature water damages the surface of
my steel bathtub?

12 hours? 24? 96?


And everything was well. Until a few months later, I moved the foam
and the surface of the tub was damaged at the bottom. The water would
drain out at the end of every bath, except for part of the lowest inch
or less. That never drained and that's the only place the damage was.

It was probably not the water, but either some residue from the foam or
trapped minerals that caused the problem. In a porcelain coated tub, water
should be able to sit in it for months. If you have very hard water, some
of the minerals may be deposited on the surface.

If you still have stuff on the tub surface, try CLR or Lime Away to get rid
of it.