Inspectioneering Journal

Composite Repair Targeting Corrosion Under Insulation

By Casey Whalen, Global Engineering Manager at CSNRI. This article appears in the July/August 2021 issue of Inspectioneering Journal.


Since their introduction as a viable method of pipe repair, composites have been rapidly gaining adoption for use in the repair and maintenance of piping systems. These composite repair systems generally consist of a filler material for reshaping the pipe surface, an adhesive primer to act as a coating and bonding agent, and lastly, the composite material itself to provide strength and rigidity back to the pipe system. Perhaps one of the key aspects of a composite material is its ability to be highly versatile. From small, 1-inch pipes to large flare lines, to drums and tanks, composite repairs can be designed for very specific scenarios using standard stock material. With the ability to change resins in order to address different temperatures and chemical compatibility needs, it comes as little surprise that composites are used across pipes and vessels carrying water, acidic chemicals, hydrocarbons, gas, and many other products.

One area where composite repairs have been seen to have a large benefit revolves around corrosion under insulation (CUI). CUI generally occurs when water gets into or under the insulation material due to weather, water-based cleaning, fire suppression systems, or any other number of ways. There are several different types of CUI including galvanic, alkaline, acidic, or chloride corrosion. In almost all cases, the key component is that water containing various chemicals ends up in direct contact with a susceptible pipe, and since insulation is not airtight, it creates an environment of high potential for aggressive corrosion to occur. Once damaged, the defect will continue to grow unless the pipe is segregated from the corrosive environment once more. In many cases, the damage that has already been inflicted can be detrimental to the service of the pipe and may need to be repaired.

Many articles and research papers exist that go into details regarding CUI causes, prevention, and inspection methodologies. However, most articles do not focus on restoration and assume that the only practical options are an immediate cut and replace or recoat for continued service or future replacement. However, a solution now exists that is being more commonly used, which involves the use of composite material to mitigate light CUI damage and/or repair and restore structural strength to the piping system.

Benefits of Composites

First, a composite repair can be used as a preventative measure or early mitigation tool. In cases where the damage is non-existent or not severe, minimal layers of a composite system can provide multiple benefits. The primary benefit here is...

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