Discuss the causes of metal corrosion beneath insulation layers

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Most causes of Corrosion Under Insulation (CUI) are similar to those of other types of corrosion; the main difference lies in the environment. Of course, moisture and oxygen are the main factors causing corrosion. The enclosed environment created by the insulation materials in pipes, storage tanks, or equipment can lead to the accumulation of moisture, thereby causing corrosion. Corrosion tends to be more severe because insulation materials prevent water from evaporating, and they can also act as carriers that allow water to move from one area to another, thereby facilitating faster spread of corrosion. High temperatures usually cause water to evaporate more quickly and reduce the corrosion rate. However, the surface covered by insulation material creates an environment that retains moisture, preventing it from evaporating. Traditional insulation materials contain chlorides. If they are exposed to moisture, chlorides may be released into the moisture layer on the pipe surface, which can lead to pitting/stress corrosion cracking. Acids, acidic gases, and strong bases (such as caustic alkalis and salts) are all corrosive agents that not only cause but also accelerate existing CUI.