Wellp, being that both lid and tub are physically/electrically connected at the hinge, and there’s overlap of the lid over the tub, and the latch is also electrically conductive on the opposite end of the hinge… would a separate gasket be that necessary?
You’d have to scrape off the paint on both tub and lid to make contact (and expose those surfaces to rusting), and if it’d rust over anyway, even the lightest coating, it’d break that electrical contact anyway.
Unno, I’d be happy with them as-is.
Worst case, take something like a cellphone jammer (ie, high freqs), lock it in the can, and see if any signal leaks out. If not, then chances of anything leaking in would be about as dim.