BECAUSE of advantages of light weight, case of fabrication, and high resistance to corrosion, aluminum aircraft fuel tanks have been used widely for two decades. Although it was established many years ago that dry gasoline does not corrode aluminum, pitting of the aluminum shell has occurred sometimes in the presence of badly contaminated water. One of the most important factors which influence the amount and nature of the water which is present in the tank is the extent with which this water is contaminated with iron rust and corrosion products of other metals with which it has come into contact during the handling of the gasoline from the refinery to the plane. In these isolated cases of corrosion in aluminum aircraft fuel tanks, the evidence indicates that the corrosion was caused by such water, contaminated with chlorides, bromides, or heavy metal compounds, lying in the bottoms of the tanks for extended periods.
This corrosion can be prevented by: designing tanks to permit free drainage of water to the sump; selecting metals to avoid electrolytic action; handling fuel so that it will not pick up water, iron rust, or other heavy metal corrosion products prior to the time that it is introduced into the aircraft fuel tank; applying suitable coatings to the aircraft interior; the use of Alclad sheet; employing corrosion inhibitors either in capsules inserted in the tank or as an addition to the fuel; and by periodic cleaning of the tank interiors or flushing them with inhibited solutions.