Scooterotica

Compatibility with fuel system materials Ethanol may have the dubious virtue of being a renewable energy source (which is good news if the machine using it has been specifically designed to use this fuel) but unfortunately a less desirable quality of the fuel is its corrosive nature. This is partly due to the high oxygen content. Oxygen is a very active element…in fact it reacts with almost everything. It is oxygen that turns iron into rust amongst other things. In liquid form these reactions are accelerated (consider how much quicker metals corrode in water compared to the air) and when mixed with hydro-carbon fuel, unexpected issues have been identified. Ethanol is also acidic, and this acid damages many materials.

Starting at the beginning where the fuel is added to the vehicle…the filler neck of the fuel tank is attacked. In older vehicles this often has a rubber connection. Natural rubber is quickly broken down by Ethanol. A well-known motoring organisation noticed a worrying trend involving the filler neck of a certain popular air-cooled German camper vehicle. The rubber pipe would perish allowing fuel to leak during re-fuelling and petrol smells emanating from the vehicle. When a new pipe was fitted it also would perish within six Months.

...Moving on to the fuel tank. Many older fuel tanks are made using two sheets of pressed mild steel welded together. A sealant is used to ensure a perfect seal (unlike water, petrol has no surface tension and will leak through the tiniest of gaps). Ethanol will react with this sealant releasing it as a gooey substance into the fuel. Instances have been found of fuel tanks that have been efficiently sealed for decades being damaged by Ethanol in petrol. Even the metal itself is not safe. Hydrogen bonding causes Ethanol to be hydroscopic to the extent that it readily absorbs moisture from the air. In a humid country like Britain this equates to a significant amount of water being added to the fuel and the steel (which has now had its protective layer stripped off by the Ethanol) begins to oxidize (rust).

Ferrous metals are not the only ones to be adversely affected by Ethanol. Copper fuel pipes, brass fittings etc are also corroded. Moving parts in fuel pumps (including rubber diaphragms if they have them) are damaged. Fuel filters are rapidly blocked by the residue of all these reactions. Rubber petrol pipes will break down and crack leading to fuel leaks. Carburettors and the jets inside them are also corroded by Ethanol. Ethanol also attacks cork (often used as a gasket in older carburettors). Below is a list of materials known to be damaged by Ethanol…the list is not exhaustive.

Zinc and galvanised materials, Brass, Copper, Terne plate (lead/tin coated steel), Aluminium, Magnesium alloys, Zamak 5, Polyurethane, Polymers containing alcohol groups, Fibreglass-reinforced polyester and epoxy resins, Shellac, Acrylonitrile butadiene styrene (ABS), Polyvinyl Chloride flexible version (PVC), Natural rubber, Polyethylene Terephthalate (PET), Cork, Petseal, Nitrile rubber (NBR) [Buna N] with low acrylonitrile (CAN) content, Viton A, Polyamide 6 (PA 6) [Nylon 6], Polyamide 66 (PA 66) [Nylon 66].