Pipe Coatings and XOX: A Belt-and-Suspenders Approach to Combating CUI

Using a Corrosion Inhibitor to Defend Against CUI

One of the primary design considerations in a piping system is to ensure that it lasts as long as possible while avoiding unscheduled down time. There are a number of methods that system designers employ in order to adequately prepare a system to withstand the rigors of its application without subjecting the system to unnecessary shutdowns. Part of these “defensive” methods includes creating a system that inhibits corrosion under insulation (CUI).

In order to set up a piping system for success, designers often specify a pipe-coating as a preventative step toward combating CUI. Coatings vary by application and are typically either sprayed on or applied with a brush or roller. Most coatings used in high-temperature, industrial applications are made out of silicon/silicone.  The coatings that are used to inhibit corrosion can function in several ways; however, the primary idea behind coatings is to seal the pipe against conditions that promote corrosion, such as moisture intrusion and/or chloride contact. A properly applied coating serves as a barrier between the pipe and the moisture, disrupting the chemical reaction that often causes corrosion.

While most coatings typically only interact with the pipe surface (serving as a shield between the pipe and moisture) and must be applied before the insulation is installed, Johns Manville Industrial Insulation Group offers an additional component to strengthen the shield between the pipe and moisture.

We have engineered Thermo-12® Gold calcium silicate and Sproule-WR 1200® expanded perlite with a corrosion inhibitor called XOX™. This is a unique approach that provides protection even after water has entered the system. XOX not only coats the pipe, but it also neutralizes corrosive chemicals that are common in industrial environments (petrochemical, refinery, power generation, etc) that typically enter the system through moisture ingress.

When water enters the system, it activates XOX, causing a chemical reaction that puts two different processes to work. The first is that silicate anions in the insulation use the water to travel to the surface of the pipe. Once there, they settle on the pipe surface, creating a passivation layer between the pipe and the insulation – very much like the typical coatings that many installers apply prior to installing the insulation. The water also activates corrosion inhibitors, which have the ability to locally neutralize most of the corrosive contaminants that may enter the system.

While most systems require a fairly acidic environment to corrode (pH < 7.0), XOX is a chemically basic material (pH > 7.0). As such, it acts as a buffer to inhibit the potential for most forms of typical corrosion to occur.

Traditionally, coatings are applied prior to the insulation installation and in accordance with the manufacturer’s recommendations to ensure that they perform as advertised. XOX differs in that it is present and ready in the insulation from the moment that it is put on the pipe and activated by any moisture. Industrial insulations that include a corrosion inhibitor, like XOX, have the advantage of insulating, while simultaneously protecting piping systems by both coating the pipe surface (creating a passivation layer) and neutralizing corrosive elements (maintaining pH >7) that typically enter the system.

During the design phase, it is critical to take a proactive approach against CUI, and this includes selecting the appropriate coatings and insulation for the application. When the system requires the use of pipe insulation, corrosion inhibitors within the insulation can dramatically reduce the potential for corrosion under insulation, which can extend the useful life of the system.