Influence of Robust Drain Openings and Insulation Standoffs on Corrosion Under Insulation Behavior of Carbon Steel

Abstract

CUI (corrosion under insulation) is among the key concerns for the integrity of process equipment and pipelines. Various measures to detect and fix the damages from CUI pose significant maintenance expenditures in hydrocarbons processing facilities. The key reason behind CUI is the limitation of thermal insulations to absorb the moisture and soak the underneath metal from wicking action. Other than CUI, trapped moisture in the soaked thermal insulations causes heat loss from process systems, thereby posing the risk of additional damage mechanisms and increased operating expenditures. This study addresses the impact of robust drain openings and insulation stand-offs on the CUI rate of carbon steel under four different testing conditions namely isothermal wet, isothermal wet-dry, cyclic wet, and cyclic wet-dry, respectively. Corroded specimens were further characterized using surface topography and scanning electron microscope. The impacts of temperature and moisture cycling on the corrosion attributes were also characterized using the linear polarization resistance method followed by an investigation of corrosion modes via optical microscopy. Insulation stand-offs in conjunction with robust drain opening resulted in the lowest corrosion rate. With insulation stand-offs and drain openings, the cyclic temperature conditions caused higher metal loss than that in isothermal conditions.

In Situ Monitoring of Corrosion under Insulation Using Electrochemical and Mass Loss Measurements

“…The small values of the R film for CS over time indicate that the corrosion products on the surface were porous, nonprotective, and easy to peel off. This phenomenon was reported in other publications and was also observed after the setup was disassembled [5,34]. The decrease in R f ilm of SS can be attributed to the breakdown of protective films formed on the surface.…”

“…Most of the remaining oxide films were found at the bottom of the pits. This nonuniform deposition of oxide films may induce further differential aeration cells [34], in which regions of the metal surface beneath oxide films are the local anodes, whereas the regions of the exposed surface are the cathodes [20]. This may further accelerate localized corrosion and in turn aggravates the mass loss [20].…”

Corrosion Performance of Buried Corrugated Galvanized Steel under Accelerated Wetting/Drying Cyclic Corrosion Test

“…The two elements, oxygen and silicon, were evenly distributed in the corrosion products of all of the coupons, from 50 to 1600 wetting/drying cycles. The corrosion products developed in the present accelerated wetting/drying corrosion test were formed via electrochemical processes represented by the following chemical reactions [44,45,47]:…”

Research on Interface Modification and Thermal Insulation/Anticorrosive Properties of Vacuum Ceramic Bead Coating

“…Much equipment, such as petrochemical industry and thermal pipelines, have been in service at approximately 150 • C. The insulation layer is easy to be thermally aged and cracked under service temperature, which provides a path for the infiltration of corrosive media. A large number of infiltrated corrosive media are accumulated and held between the insulation layer and the protective layer [1][2][3], and the anti-corrosion layer on the surface of metal pipelines will soon fail [4][5][6]. Therefore, the development of thermal insulation and anti-corrosion coating is of great significance for this field.…”