So with one Corrosive all other weapons hitting the target get the benefit? Where is this tested or stated? I'm not saying it's not true but this is the first time I'm reading it.
Any corrosive weapon gives you a 25% damage bonus whilst active (you see the little icon on the target display) and that's it. Only need the one, weapon size isn't a factor for it either.
I have no idea where I read that.