NACE SP21433-2019

The buried or below-grade sections of electric utility steel transmission and distribution structures are often subject to corrosive environments and are not easily accessible for visual inspection. Prior to the publication of this standard, no industry practice existed to help electric utilities determine a prioritized listing of structures to be inspected or that described an inspection and assessment procedure to evaluate below-grade corrosion problems.

This joint NACE/IEEE standard is intended for use by electric utility personnel, contractors, inspectors, and those interested in the impact of corrosion on the below-grade sections of transmission, distribution, and substation steel structures. It provides requirements to:
(1) help utilities identify structures that may be at a high risk for below-grade corrosion;
(2) excavate and inspect the selected structures;
(3) categorize the condition of structures based on corrosion degradation;
(4) prioritize structures requiring additional inspection based on those findings; and
(5) help identify next steps as required.

This standard is limited to the inspection and assessment of weathering steel transmission towers, poles, substation structures, and other similar structures.