FRG & Methanol:
Although some types of corrosion
(galvanic, aerobic, pitting and inter-granular) do not affect fibreglass, FRG may be subject to chemical attack from hydrolysis, oxidation, or incompatible (Alcohol/Methanol) solutions.
manufactured prior to 1991 may not be compatible with gasoline (diesel?) containing ethanol. It has been reported that, in the presence of ethanol, some resins may be drawn out of fiberglass
and carried into the engine
where severe damage could occur. If an older fiberglass tank is used, check with the manufacturer to determine if gasoline with ethanol can be safely used.
There are some resins that are immune to ethanol (some vinylesters, for example) and are used in underground gasoline storage
tanks, but most resins, including common epoxies are not able to withstand contact with ethanol.
“Rubber” (Neoprene, Buna-N, Nylon etc) fuel
lines, gaskets, o-rings etc may also be affected by ethanol.
Results of BoatU.S. Sponsored Fuel and Fiberglass Gas Tank Tests ~ Seaworthy
magazine (January 2006)
behavior of aluminum
alloys in the presence of Ethanol”
“Can You- Should You- Build Your Own Fiberglass Tanks?” ~ by Ken Hankinson (Practical Sailor)