can invincibility from items stack?

Currently I got an unique top that increases the invincibility time after I get hit by 2 seconds, making up a total of 3 seconds invincibility.

My question is, if i get, lets say, a bottom wear that increases my invincibilty by 2 seconds as well, can both potential bonuses stack and give me 5 seconds invincibility after getting hit?.

If this is possible it could solve the potion cooldown issue in some boss fights

Well, Empress Cygnus can also cancel potential on equips, regarding your last point. Good question, though.

Only tops and overalls can get that potential so the only question is whether 2 lines of that bonus (eg. +2sec +1sec) stacks.