man spraying external endoprene coating on an underground fuel storage tanks

Underground Tank coatings

The outer coating of an underground tank plays an important role in its overall performance

The coating applied to the outer skin of an underground tank plays an important part in protecting the skin from corrosion and preventing any deterioration in its performance.

Over the years the choice of coatings available to protect underground tanks has increased, however the coating choice needs to be decided on with consideration to the material that will be used to back fill the tank once in place.

The guidelines regarding backfill material as laid out in En12285-1 are as follows :

  • The backfill used should be non-cohesive granular material which will surround the tank to give adequate support and restrain.
  • The choice of backfill used can depend upon the native soils and their compatibility with the coating of the tank.
  •  All backfill material should be washed, graded and free flowing, free from ice, clay, organic materials and free of heavy objects. The minimum bulk density should be 1 500 kg/m3.

The standard mentions 5 possible materials that can be used to coat underground tanks:


This is no longer widely used as the bitumen required additional treatment and the mixing of reinforcing fibres, it is also difficult to apply.


Epoxy coating are used but require precise mixing and application


This can be found among a number of European manufacturers and has some advantages over steel outer skins, however it is more difficult to work with and is prone to damage during transport and installation.


This is by far the most common material used to coat the outer surface of underground tanks. Supplied under the trade name of Endoprene©, it is bright yellow or plum colour and is a common site. Its combination of excellent performance characteristics with ease of application makes it the popular choice among tank manufacturers worldwide.


PVC coating are very uncommon