I have two fermenting vessels in the garage on metal shelving. Painted metal shelving. To be accurate they actually sit on some inch thick wood that sits on the metal shelves as the metal gets very cold at this time of year. In fact to keep things cosy I wrap around some insulation blankets normally used for hot water tanks.
Anyway I was bottling my attempt at a clone of Bishops Finger when I notice that the yeast (WYeast Activator 1275 - Thames Valley Ale) had been a bit shall we say vigorous. So vigorous in fact that it had forced its way out of the top of the FV and spilled down the back of the FV between the insulation blanket and between the planks of wood and pooled on the metal shelf. None of this was visible from the front and it must have been there about a week. What surprised me was where the yeast had pooled on the metal shelf, it had managed to eat through the paint of the shelf.
The clean up took ages and things have been left to dry out overnight. It would be enough to put a sane man off brewing for life. Fortunately I don't meet that criteria