Buried piping without adequate cathodic protection should be included in external inspections. What area must be inspected?

Buried piping without adequate cathodic protection should be included in external inspections. What area must be inspected?

• A. The interior of the pipe
• B. The exterior coating only
• C. The soil-to-air interface shall be included in the external inspection schedule
• D. The buried pipe support foundations

Answer: (C)

When buried piping lacks adequate cathodic protection, the most vulnerable area for external corrosion is where the pipe meets the soil and the air—the soil-to-air interface. This zone is exposed to moisture, oxygen, and soil chemicals that drive corrosion, especially if the coating is damaged or degraded and the protective current from CP can’t reach the metal effectively. Inspecting this interface helps reveal coating holidays, disbondment, moisture intrusion, or other conditions that foster corrosion, which might not be visible higher or lower in the soil. Interiors aren’t exposed to external conditions, so they aren’t the focus for external CP-related corrosion. Checking only the exterior coating misses damage at the soil surface where the corrosion cell is most active. Buried pipe support foundations can influence conditions, but they don’t pinpoint the primary area where external corrosion risk concentrates when CP is inadequate.

When buried piping lacks adequate cathodic protection, the most vulnerable area for external corrosion is where the pipe meets the soil and the air—the soil-to-air interface. This zone is exposed to moisture, oxygen, and soil chemicals that drive corrosion, especially if the coating is damaged or degraded and the protective current from CP can’t reach the metal effectively. Inspecting this interface helps reveal coating holidays, disbondment, moisture intrusion, or other conditions that foster corrosion, which might not be visible higher or lower in the soil.

Interiors aren’t exposed to external conditions, so they aren’t the focus for external CP-related corrosion. Checking only the exterior coating misses damage at the soil surface where the corrosion cell is most active. Buried pipe support foundations can influence conditions, but they don’t pinpoint the primary area where external corrosion risk concentrates when CP is inadequate.