Be aware of pipe corrosion beneath the insulation layer

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Example: A stainless steel pipe is used to transport a hot (80°C) weakly acidic solution. There is an insulating layer outside the tube to maintain the temperature. The insulation material is covered with an aluminum waterproof layer, and the pipes have been in use for several years without any problems. Due to the marine environment, the pipeline support frames suffered corrosion; to repair them, the aluminum covers and insulation materials were removed, and they were reinstalled after the repairs were completed. But just a few months later, the repaired pipe section leaked. Inspection shows that stress corrosion cracking has occurred on the outer surface of the stainless steel pipe. The reason is that the repair workers did not install the aluminum covers properly as required, failing to provide protection against rain. Rainwater seeps in, wetting the insulation material. Chloride ions from rainwater and those leached from insulation materials accumulate and concentrate on the surface of stainless steel pipes. Combined with the residual stresses present in the pipeline, this led to chloride stress corrosion cracking, with the cracks penetrating and causing leakage. Comment: Here again, corrosion is caused by poor maintenance quality. During equipment maintenance, it is often necessary to remove the insulation layer, and it should be restored in accordance with the requirements of the construction specifications after the maintenance is completed. During the operation of the equipment, the insulation layer may sometimes get damaged, and it should be repaired promptly once damage occurs. For stainless steel equipment and pipes, it is very important to prevent the insulation layer from absorbing moisture and becoming wet.