Corrosion risk planning – 2 – Above ground storage tanks – oil and gas- PART 1

 Above ground storage tanks

1. Inner walls

      • Coating degradation
      • Corrosion due to water/dissolved oxygen
      • insufficient/damaged cathodic protection system
      • dissolved sacrificial anodes

2. Outer walls/roof

      • Atmospheric corrosion
      • coating degradation due to moisture + UV radiation + temperature
      • Erosion and wear due to wind and dust particles
      • biological growth at the bottom areas near soil
      • soil corrosion near the bottom

3. Pipes

      • Atmospheric corrosion
      • Coating degradation
      • mechanical failure
      • internal corrosion due to water/dissolved oxygen
      • crevice corrosion in areas facing away from atmosphere
      • corrosion at welds and joints
      • microbial corrosion at 6 o’ clock positions
      • erosion corrosion at bends

4. Railing

      • Coating degradation
      • Wrong coating selection based on pure aesthetics
      • coating damage at joints and bends
      • corrosion at welds in the railing
      • crevice corrosion at fixtures
      • pitting corrosion

5. Breather valve

      • uniform corrosion/pitting depending on whether it is made up of carbon steel/stainless steel
      • Galvanic couple at the joining/welding point of valve to roof
      • corrosion after damage of galvanized layer

6. Spray nozzle

      • Crevice corrosion at orifices
      • clogging
      • erosion and mechanical damage at orifices and bends
      • crevice corrosion at fixtures

7. Manhole

      • corrosion at edges of cover
      • galvanic corrosion at contact points with neighbouring parts
      • pitting due to chloride ion contact
      • crevice corrosion at fixtures
      • pitting corrosion at welds

8. Lagging

      • pitting due to chloride ion contact
      • crevice corrosion at overlapping joints
      • water seepage at insufficiently bonded overlaps

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