API
API 583
Corrosion Under Insulation and Fireproofing
Dedicated guidance on CUI: where it occurs, which temperature ranges and service types are susceptible, insulation and cladding design, and inspection strategies for damage that is hidden by definition.
This is an explanation, not the standard. PipingInspector is not affiliated with API and reproduces no part of the document. Always work to the current edition of the standard itself and to your project specification.