External Corrosion Protection

Below are advantages of choosing Polyurethane as a surface coating for underground storage tanks:

• Excellent hardness and impact resistance

• Good elasticity because of the relative thin coating layer
• Long term resistance to UV and sun light
• Perfect adherence to steel
• Less prone to transport damage
• Easy to see a surface damage
• On site repairable
• Very good resistance to:
  • All fuels
  • Micro-organisms contained in soils
  • Alkaline and Acidic Water Solutions
  • Salt Water

External Corrosion Protection
Underground Tanks

Coating Material   Minimum
External surface
coating tested to the following minimum
test voltage V
Bitumen With fabric reinforcement


14 000
Without reinforcement 5 20 000
Epoxy   0.7 6 000
Glassfibre (GRP)   2 15 000
Polyurethane   0.8 6 000
PVC   1.25 10 000
Note: The minimum test voltages indicated are related to the minimum thickness mentioned in this table. If the thickness is increased, the voltages should also be increased. Coatings can be tested at higher voltage than indicated.

Ref: EN12285-1 Table 7 P19

External Surface Treatment
Aboveground Tanks

Minimum Thickness – DFT

Sigma – Base Coat


Sigma – Top Coat

40 μm


Tanks are offered in standard colours as below:

Dust Grey


Sky Blue

Signal White RAL9003
Graphite Black RAL9011

Other colors can be offered as per customer’s specification,
however this might be at an additional cost.




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