CUI is the silent killer of process piping. Here's how the best contractors design it out.
Corrosion Under Insulation (CUI) is among the most costly hidden failure modes in process plants. By the time CUI is visible from the outside, the damage to the substrate is often significant.
The CUI temperature window is well understood: typically -4°C to 175°C, where moisture can enter the insulation and remain in contact with the substrate. Above and below this range the risk drops sharply.
Prevention starts with the right primer. Modern epoxy phenolic and inert multi-polymeric matrix coatings dramatically extend the substrate life under insulation. Specifying the right primer system is non-negotiable for CUI-prone services.
Insulation material matters too. Hydrophobic mineral wool and closed-cell PIR/PUR systems reduce moisture ingress. Vapor barriers, where used, must be continuous and properly sealed.
Cladding is the first line of defense. Properly lapped joints, sealed terminations, and silicone-sealed penetrations keep water out. Once water is in, the insulation acts as a sponge — and corrosion accelerates.