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New metal jacketing product helps combat CUI

Jun 20, 2023Jun 20, 2023

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Corrosion under insulation – it’s an uphill battle and a huge concern for engineers, specifiers and for those maintaining an industrial insulation system.

A large portion of the maintenance process for industrial facilities is focused on the prevention and treatment of corrosion under insulation (CUI).

Despite insulation systems being designed to deter ingress of water and other harmful substances, over time damage often occurs and infiltration is essentially inevitable. When a system is damaged or exposed to the elements, liquid substances like rain/flood water or chemicals can enter a system, become trapped, and begin interacting with the underlying piping or process equipment, leading to corrosion. If left untreated, CUI can lead to catastrophic consequences.

Most often, the only reactive way to resolve CUI is through regular maintenance, which includes the removal of both the metal jacketing and underlying insulation on piping or equipment and replacing these materials if necessary. This process requires costly labor, facility shutdowns and material upgrades.

When does CUI usually occur?

What's the impact?

A better solution

Mitigate the potential for corrosion under insulation, with Cross-Flo™ Jacketing* – a new innovation from Johns Manville. Cross-Flo metal jacketing is an effective tool for aiding in the rapid removal of water from an industrial piping system. Unlike standard protective jacketing products, it provides a pathway between the industrial insulation and jacketing for infiltrated water to drain to a low point and escape when a weep hole or drainage port is present. The pattern promotes cross-directional flow (CDF), a mechanism whereby liquid can travel in any direction regardless of installation orientation, reducing “dead spots” where unwanted moisture can pool throughout a length of pipe.

Many industrial insulation products are produced with features to prevent water from migrating through the insulation to the metal substrate beneath. Most experts agree that it is nearly impossible to fully prevent water ingress into an industrial insulation system, so it makes sense to focus instead on how to best facilitate water egress as quickly and thoroughly as possible from the system.

If the amount of time that water is present in the insulated system can be reduced, the chances of CUI occurring are dramatically reduced.

Cross-Flo Jacketing reduces the risk of CUI by minimizing the time unwanted water remains in the system. To test the efficacy of Cross-Flo Jacketing, simulation testing was conducted in which 100mL of water was allowed to drain through representative insulated pipe sections covered with aluminum jacketing with Cross-Flo, smooth, and stucco embossed patterns. Tested insulation types included calcium silicate, perlite, mineral wool, and silica aerogel.

These results emphasize the superior drainage capabilities when choosing Cross-Flo Jacketing for CUI protection. Whether rigid, non-rigid, hydrophobic, or non-hydrophobic insulation is used, Cross-Flo jacketing demonstrates significant improvement in removing water from insulation systems, helping to prevent CUI.

Added benefits

Aside from the risk mitigation of CUI, Cross-Flo Jacketing has various added benefits:


To learn more about Cross-Flo Jacketing and the testing performed, visit the Testing Summary Bulletin.

To request a free Cross-Flo Jacketing sample, visit Cross-Flo samples.

*Patent pending

**Cross-Flo reduced the time to drain of 100mL of water up to 80% in small-scale simulation testing over a 3” insulated pipe. Testing data is noted on our technical bulletin on

When does CUI usually occur?What's the impact?A better solution, Cross-Flo Jacketing performed better than smooth and stucco embossed jacketing with every insulation type testedCross-Flo drained the water in just 27 secondsAdded benefitsResources