Corrosion

CORROSION: THE HIDDEN DANGER - ARTICLE TAKEN FROM OCTOBER 2005 ISSUE OF WORLD PIPELINES

THE PROBLEM OF CORROSION UNDER INSULATION

When designing process plant, insulation selection is sometimes thought of as being less important than other capital investment decisions. The insulation chosen can play a critically-important role in the corrosion process.

The most serious problems associated with corrosion under insulation are sudden unanticipated failures of the system and the high value of the equipment involved. Common costs include the repair of corroded piping and equipment, costly lost production time, increased potential of leaks and catastrophic failures such as fire and explosion.

FOAMGLAS® insulation resists the development of corrosion in three ways, by:

• minimizing water intrusion and retention
• not contributing to the corrosion of carbon or stainless steels
• being an integral component of a corrosion-resistant barrier.

Three approaches can help prevent the problem of corrosion under insulation:

• Vapour barriers
  This is the most obvious defence, but they are susceptible to perforation and damage.
  
• Other barriers
  Other barriers such as paints or mastics can be used to physically prevent water from coming in contact with critical equipment. With these materials surface preparation is critical and a defect-free coating is essential but not easily achieved. Aluminium foil can also be used as a physical barrier as well as a cathodic protection layer.
  
• Proper insulation
  A third alternative is the use of an insulation that minimizes water intrusion, will not retain water and will provide the best possible conditions to prevent metal corrosion.

Tried and Trusted

For decades FOAMGLAS® has been chosen as the best, most impermeable, insulation material to protect against the dangers of corrosion under insulation. FOAMGLAS® is completely impermeable (μ = infinity) and will not absorb water. A FOAMGLA® insulation system can be simpler than systems using permeable insulation materials. FOAMGLAS® does not rely on secondary protection methods to keep moisture out: it is an effective and reliable barrier for a wide range of temperatures.

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