This is why I wont use silicone on a tank. This is the brand of instant gasket we use, nowhere on the tube does it say its ok with fuels, water oils ect yes.
Our fitter replaced a cork gasket that had broken on top of a fuel tank while it was in for a service.
Less than a fortnight later its leaking and the silicone has gone all mushy
The 3m gear stays intact.