As science and technology have evolved, so has humanity's understanding of the way different chemicals and compounds react to each other, and many mixtures which were thought safe in the past are finally understood to be otherwise. While a necessary component for human beings, plants and animals, zinc can wreak some fairly serious damage on diesel fuel and systems using diesel fuel.
One of the most pressing issues with zinc within diesel fuel is the way it interacts with the fuel itself, causing it to break down more quickly than it would under normal conditions. If the temperature is kept stable at around 68 degrees F the fuel can remain stable for around 12 months or even longer, but the introduction of zinc within the fuel causes it to break down down faster. As diesel begins to age and break down it creates harmful sediments and a sticky substance known as gum which can then block the reaction of diesel with oxygen, thus affecting the overall efficiency of the engine and eventually leading to complete engine shutdown unless frequent filter changes occur.
When zinc is introduced to diesel fuel it begins to break down into unstable compounds which can then coat the various components and working surfaces of the engine, eventually covering the catalytic converter as well. Once this has happened the zinc becomes a catalyst contaminant which then transfers into the exhaust and out into the atmosphere, creating harmful vapors which can be poisonous if inhaled in large quantities. It is for this reason that there are regulations against zinc-plated fuel tanks and transportation tanks.
Zinc reacts differently than metals such as aluminum and steel to diesel fuel. Regardless of which type of tank diesel fuel is stored in, water from condensation will always enter the fuel and eventually settle to the bottom of the container. A barrier of bacteria then forms between the fuel and water, and those bacteria will use zinc as a food source, eventually penetrating the layer and corroding the walls of the tank far more quickly than steel or aluminum, since they do not create such a nutrient-rich environment for the bacteria to work with. Most modern tanks include filtration devices which allow for regular draining and filtering of the water from the tank to avoid corrosion build-up.
