Modern fuels cause problems with Fibreglass and Composite tanks, the resins that are already in the fuel tank structure are susceptible to attack from the chemicals that are now in modern fuels, normally this presents itself by the fuel tank becoming porous.
The visual signs for this are the following
1. Strong smell of fuel on the outside
2. Decals and stickers start to shrivel, or bubble up, and eventually come of
3. Paint will start to bubble, and discolour similar to below.
Once the tank has been prepared and then Caswell Fuel Tank Sealer applied this will solve the problem.
If you intend to repaint the tank after sealing, we advise that you unless the tank has been standing empty for a period of time, that you leave for 4-6 weeks before doing this, as there will still be ethanol in that tank structure, it will not be able to go back in the tank, as the Caswell Sealer will stop that, so it will work its way out towards the paintwork, and will react with any fresh paint that has been applied.
Normally over 4-6 weeks all ethanol fuel should have evaporated, and the tank can be painted, and its best to seek advice on the best primer to use.