The most recent estimates from the National Association of Corrosion Engineers (NACE) put the global cost of corrosion into the trillions of dollars1. These costs include corrosion in the industrial industry where corrosion under insulation (CUI) has been plaguing the industry for decades. To help combat this, industry experts have come up with a number of different technologies and methods to help prevent corrosion.
While there is no guaranteed method that will preclude CUI 100% of the time, there is one guiding principle behind each of these preventative technologies: inhibit water from contacting the pipe surface. Of course, this is more easily said than done. Any minor flaw in either the insulation or the jacketing increases the risk for water intrusion. To preemptively address this, savvy designers will typically select insulation materials and implement design components that can help prevent CUI before it occurs.
Many system designers will start by selecting a pipe coating to cover the pipe. Pipe coatings prevent water or corrosive substances from contacting the pipe surface. There are a number of different types of coatings in use today, including thermal spray aluminum (TSA), zinc coatings, and epoxy coatings. It’s important to understand that most coatings have an upper temperature limit ranging between 300°F and 400°F. For systems that operate beyond these temperatures, designers shouldn’t rely on a pipe coating as the sole method for preventing CUI as it will no longer be able to serve as a barrier between water and the pipe. This may be because the coating has physically burned off, or because it has undergone “galvanic reversal,” an issue that only applies to zinc coatings.
This is where other strategies can be implemented to work with the coating as a “belt and suspenders” approach. For example, some insulations are manufactured with a hydrophobic treatment that will actually prevent water from penetrating into the system. Most hydrophobic treatments are silicon based and are applied either as a coating on the outside of the insulation or as an integrated part of the insulation during the manufacturing process. Most hydrophobic treatments have an upper temperature limit of 600°F – beyond this temperature they will begin to burn off and become ineffective. There are three common hydrophobic insulations: InsulThin™ HT (a thin, microporous blanket for high-temperature applications), Sproule WR-1200® (expanded perlite, ideal for many applications in the gulf coast), and silica aerogel (a thin, aerogel blanket).
For systems that operate at temperatures above 600°F, the outer layer of insulation will likely remain hydrophobic, however the inner layer that is next to the pipe will lose its hydrophobicity. As such hydrophobic insulations should not be considered the be-all-end-all solution for CUI prevention. At these higher temperatures we recommend using products like Thermo-1200® calcium silicate or Sproule WR-1200 expanded perlite, insulations that are manufactured with XOX™, an active corrosion inhibitor.
XOX is an integral part to Thermo-1200 and Sproule WR-1200, and it offers a two-pronged defense against CUI. First, the corrosion inhibitors actively neutralize corrosive ions that enter the system through water ingress, and second, XOX combines with the water to create a silicate coating that settles and hardens on the pipe surface. This coating works just like other coatings by preventing water from touching the pipe; however, unlike other coatings, the efficacy of the XOX silicate coating is unaffected by the operating temperatures of the system. For systems that operate at temperatures at or below 1200°F, Thermo-1200 and Sproule WR-1200 are excellent components to a proactive CUI strategy.
Finally, many system designers recommend drilling holes through the insulation at the bottom of the pipe. This allows any water that has entered the system to drain in case it can’t escape through the insulation itself. As the holes are at the bottom of the pipe, gravity prevents any water from using the holes as a point of ingress into the system.
By selecting materials and incorporating design elements that can help prevent CUI, system designers can take a proactive approach that addresses CUI even before water has entered the system. If you have additional questions about hydrophobic insulations or the corrosion inhibitor XOX, please contact our technical team. We will be happy to discuss where you can find additional resources as well as answer your questions about the materials you can use to prevent CUI.
We will also be hosting a live webinar on June 7th discussing the findings from cutting-edge CUI research, the importance of real-world application testing, and the evolving future of CUI testing. Join us for CUI Research: Critical Components and Findings, as Leo Caseres, PhD., from Southwest Research Institute, and Ames Kulprathipanja, PhD., from Johns Manville, reveal the innovative research that is at the forefront of evolving CUI prevention technology.
- Study Sets Course Toward Corrosion Management Practices to Increase Safety, Decrease $2.5 Trillion Global Cost of Corrosion.