CUI Inspection - Corrosion under insulation

Element supports clients from a wide range of industries to assist in evaluating solutions using CUI inspection to help mitigate corrosion under insulation.

CUI inspection aids in identifying metal corrosion that occurs due to moisture and oxygen exposure. Often undetected for long periods, subsequently causing damage to the infrastructure, which can become hazardous and costly to repair. In severe cases, the damage caused is followed by costly site remediation, long downtimes, and legal issues. 

Corrosion under insulation typically occurs as a result of moisture infiltration on insulated carbon and low alloy steel equipment, which is operating at high temperatures with cyclic service in the CUI temperature range. Moisture trapped under or within the insulation can create an extremely aggressive environment, accelerating the rate of corrosion. 

Mitigating CUI, the role of coatings 

Protective coatings are often utilized in conjunction with installation design, insulation choice, and inspection regimes as part of a systems approach to CUI prevention. In such cases, the selection of an appropriate coating requires an understanding of the performance characteristics of the material subject to both high temperature cyclic and CUI conditions. We provide a wide range of specialist Coatings Testing Services.

Several industry bodies have published documents and standards related to the mitigation of CUI, including standards specifically relating to coatings. This includes ISO 19277: 2018, which identifies several classification environments upon which coatings are evaluated. Depending upon the intended operating temperature (including cryogenic testing service),  tests are conducted on both standard cured and heat conditioned samples for CUI categories 1, 2, and 3.

CUI inspection methods

Element Materials Technology offers a variety of testing to verify performance for suitability under insulation in accordance with ISO19277:2018, which include: 

• Heat conditioning. Cyclic heat conditioning of coatings based upon the CUI category of choice. 
• Adhesion. Evaluation of heat conditioned and standard cured materials both pre and post-exposure. 
• Artificial aging. Environmental exposure in the form of neutral salt spray and water immersion. 
• Thermal cycling test. Repeated heating and cooling over multiple cycles from the maximum temperature of the relevant CUI category, then quenching into cold water.
• Multi-phase CUI cyclic corrosion test. A horizontal square pipe test is utilized to simulate a typical environment where CUI occurs; the test process includes dry heat, thermal shock, immersion in boiling water, steam interface, and shut downtime. 
• Cryogenic exposure. Optional cryogenic cyclic testing for cryogenic categories described in the standard.
• Vertical pipe test (Houston pipe test). An optional CUI test method to evaluate the resistance of a coating to accelerated CUI conditions with shut down periods. The test includes wet/dry/heat/cool cycling of an insulated coated pipe for a total of 30 cycles. 

In addition to standardized test protocols, our engaged experts can provide bespoke corrosion under insulation testing programs for R&D, including testing of alternative materials and modified test regimes.

The Element advantage

Our coatings specialists have several years’ experience working in CUI products and testing and can provide expertise to help you with your requirements. 

For more information about the corrosion under insulation testing and CUI inspection or to request a quote, contact us today.