Understand the moisture loop
In many tank installations, mineral wool insulation wraps around the tank shell and roof and is then covered with metal sheathing. Over time, that system becomes compromised. As water enters, it saturates the insulation, often reaching 30 percent water content, as reported by multiple terminal owners. This insulation holds moisture directly against the tank’s steel surfaces.
That moisture evaporates due to the tank’s heat, condenses on the underside of the cladding, and drips back into the insulation. The result? A closed-loop moisture cycle accelerates corrosion in areas that are often difficult to inspect without removing the entire insulation system. The risk is further intensified in operating ranges between -4°C and 175°C, where thermal cycling exacerbates water ingress and corrosion rates. What’s the solution?
A new protection: Spray-on thermal insulation
Storage operators increasingly turn to spray-on insulation coatings to protect tank roofs. Unlike traditional cladding and wrap systems, these coatings form a continuous, water-resistant barrier that adheres directly to the steel surface.
Based on silicone technology, hydrophobic SOI coatings shed water instead of absorbing it. Its monolithic finish eliminates the seams and overlaps found in mechanical systems, which are common ingress points for moisture.
Terminal operators report a growing interest in using SOI systems on tank roofs, where mechanical systems are hardest to maintain. Because these coatings are easy to apply without banding or jacketing, they significantly reduce labour hours and eliminate many vulnerabilities that lead to CUI. Applicators can complete a single coat in one day, achieving 80 to 250 mils in thickness with minimal downtime and provide safe-to-touch properties or achieve energy efficiency targets.
Proven in the field
In one recent U.S. installation for a major integrated energy company, PPG PITT-THERM® 909 SOI coating outperformed a competing product that required six days and multiple coats to achieve the same thermal resistance. PPG’s system was applied in a single layer, cutting downtime, labour costs and exposure risks. It resulted in faster project completion, lower potential of inter-coat contamination compared to competing SOI technologies and a 5 percent cost savings compared to traditional insulation.
Another large-scale application was for a large operator. The coating’s efficiency and long-term moisture resistance played a critical role in protecting assets.
Look ahead: Beyond the roof
Tank roofs remain the focal point for SOI systems. However, attention turns toward the tank shell. Mechanical insulation on vertical walls also faces moisture ingress, especially at the seams of the outer jacketing. Though less exposed than roofs, these areas are not immune to CUI. As industry familiarity with SOI systems grows and operational demands increase, the adoption curve will likely expand. The shift from segmented, moisture-prone insulation toward continuous, high-performance systems reflects a broader push toward smarter, more sustainable terminal operations.
For more about PPG Pitt-Therm 909 spray-on insulation, click here.
For PPG’s coatings selector, click here.
Bill Pernice is the PPG Global segment director for oil and gas, protective and marine coatings. He leads strategic initiatives to advance corrosion protection and insulation technologies across the energy sector.
Originally published in Storage Terminals Magazine.
