The present trend in establishing an effective level of external metallic surface corrosion control is the application of a barrier coating or adhesive on the metallic surface prior to the application of a thermal insulating material. Experience has shown that there is generally a limited beneficial effect from the application of cathodic protection (CP) to a bare or ineffectively coated metallic surface under thermal insulation.
This NACE technical committee report was prepared as an information guide for external corrosion control of thermally insulated underground metallic surfaces and considerations of the effectiveness of CP.
Control of external corrosion on buried/submerged metallic piping systems and other structures. Use of electrically insulating coatings, electrical isolation, and cathodic protection as corrosion control methods for existing bare, existing coated, and new piping systems. Interference currents. Historical Document 1976