With respect to CUI, how well do thermal insulating coatings retard the spread of corrosion?

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With respect to corrosion under insulation (CUI), how well do thermal insulating coatings retard the spread of corrosion?


Editor's note: this question was answered in The Use of Insulation Coatings for Burn Protection, a Webinar from Corrosionpedia. See more on our Webinar page.

Thermal insulation coatings (also known as thermal barrier coatings) provide both a resistance to heat flow and a protective finish to the objects (such as pipelines and process vessels) to which they are applied.

Together with a corrosion protective primer, the system does very well to minimize or prevent corrosion under insulation (CUI).

First, there is no gap between the thermal insulation coating and the primer where water can ingress and quickly degrade the corrosion protective primer. (For more information on this topic, read The Detrimental Effects of Wet Insulation in the CUI Range.)

Second, with the temperature gradient in the insulation coating, moisture from the environment will be kept away from the metal substrate. Think of it as the opposite of the cold-wall effect, where moisture is drawn into the coating if the substrate metal is at cooler temperatures relative to the external temperature. For coating defects, like delamination and blistering, the temperature gradient should also keep moisture from migrating into the blister or delaminated area.

Third, if the insulation coating and primer are damaged and the metal substrate is exposed, resulting in rust formation at the defect, the rust will stain the area around the defect, making it highly visible so that it can be repaired well before significant metal or wall loss occurs.

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Written by Howard Mitschke
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Howard has a Bachelor of Science Degree in Biology at the University of Houston. He worked for Shell Oil Co. for 32 years and retired in 2009. During his career he worked in biochemistry, epoxy resins technology, materials testing and was a coatings specialist for 17 years. As a coating specialist he was responsible for Research & Development on many different coating issues, on technical support, writing coating specifications and for qualification of coating products. Full Bio

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