I've got a drop sheet (those ones you get from Mitre 10 for when you are painting) on the bed. It covers the whole bed under the mattress protector (which I figure can be washed later if need be) - it cost $1.25.

It's most definitely not corrosive - unless you happen to be giving birth to an alien being - I think the concern is that if it gets in to the padding in you car seats it can rot them, like any liquid would. We have leather car seats and my husband would absolutely freak out if my waters broke on his beloved leather, which he conditions by hand every month. (He's gunna get a shock when master/miss comes along and pukes!!)

I've heard it doesn't smell so flash, but I guess I will find out if that is true well enough. Of course, Alan having had it in his shoes would be able to tell us that.