The corrosion is the result of water contained in the fuel. This can be caused by water condensation on the inner walls of the tank, contaminated fuelor carelessness when filling the tank. The longer a vehicle is not moved, the more condensation can form in the system. Seasonal and irregularly moving vehicles are therefore particularly affected.
the so-called steel finger test shows how quickly rust can form. For this test a steel rod is suspended in a glass containing naphtha, to which ten percent water has been added. Then the glass is placed in an oven at 60 °C. After only 24 hours the steel rod is covered with rust.