Third Generation Polysiloxane (TGPS) ambient curing CUI mitigation coatings have been used in the petrochemical industry for over five years. These coating technologies have demonstrated positive results in lab testing as well as both shop and field application for asset management in elevated temperature, cryogenic and cyclic applications across a wide range of service temperatures. TGPS coatings have also demonstrated effective use of a two-step (primer-insulation) CUI mitigation system when compared to traditional (CUI coating-fibrous or granular insulation-cladding) systems.
Corrosion Under Insulation (CUI) is a well-known industrial problem that has been plaguing asset owners for decades. CUI presents one of the costliest corrosion factors for Oil and Gas, petrochemical and general processing industries and can result in unplanned shutdowns, maintenance, repairs or even explosions while in service. Due to the risk factors present, many methods to prevent CUI have been adopted, trying to find best practices to minimize the risk of potentially catastrophic events caused by CUI.
The CUI concept is composed of a three-component system:
1. Steel – substrate for processing chemicals (constant or in cyclic temperature operation)
2. Insulation – provides thermal efficiency
3. Cladding – protection for insulation and steel from atmospheric elements
In practice the cladding system is rarely sealed completely, so water from rain, dew, fire deluge water, steam condensation or cooling tower spray is often is able to penetrate the system through an ingress point in the cladding, generally where complex structures pose difficulty maintaining a watertight system. Additionally, where potentially permeable, moisture sensitive insulation is used, condensation build up is a frequent CUI contributor. Once water has penetrated the system at an ingress point such as a break, seam, gap, or incompletely sealed valve, water may be absorbed into the insulation, eventually causing saturation or a high concentration, and it may cause CUI if the steel is not fully protected. Potential contaminants like acid or high salt content from rain or chemicals (chlorides /sulphides) leaching from insulation systems can form highly corrosive compounds, accelerating the corrosion rate.