The most dangerous corrosion in a process plant is the kind nobody can see. Corrosion under insulation happens on pipework and vessels that look perfect from the walkway, because the attack runs under the cladding where water sits against warm steel. Industry surveys consistently place CUI among the largest single maintenance costs in refining and petrochemicals.
Why insulation makes corrosion worse
Insulation traps water from rain, washdown, deluge testing and condensation, holds it against the steel, and keeps the steel in the temperature range where corrosion is fastest. The recognised danger band runs roughly 50 to 175 C, and equipment that cycles through it, or through the dew point, corrodes fastest of all. Even in the dry UAE climate, coastal humidity, cooling tower drift and deluge systems supply the water.
What good practice looks like
NACE SP0198 is the reference practice, and its logic is simple: assume the insulation will leak, and make the coating under it the real barrier. That means immersion grade thinking on hot steel: blast to ISO 8501-1 Sa 2.5 and apply a CUI rated system, typically high build epoxy up to its temperature ceiling and specialised chemistry such as inert multipolymeric matrix coatings above it. Standard high temperature coatings and CUI systems overlap but are not interchangeable; specify for the cycling range, not the nameplate temperature.
Where to start on an existing plant
Prioritise inspection where failures cluster: below insulation terminations, at low points and supports, on lines cycling through the danger band, and anywhere cladding is visibly damaged. Budget coating renewal into the same window as the inspection, because stripping insulation twice is the expensive way.
MENA Industrial Supplies quotes CUI rated systems against specification from Dubai. Start at the oil, gas and refinery coatings page.