What is the code for external corrosion control on underground or submerged metallic piping systems?

The correct code for external corrosion control on underground or submerged metallic piping systems is SPO169. This code outlines the requirements and standards related to the prevention of corrosion, ensuring that these pipelines are protected from environmental factors that can lead to deterioration. Understanding the relevance of this code is essential for professionals involved in maintaining the integrity of pipelines, as it provides guidelines for inspection, maintenance, and the application of cathodic protection measures.

While other codes exist, they may pertain to different areas or aspects of corrosion control and may not specifically address the external corrosion protection for underground or submerged systems. Thus, SPO169 is the recognized standard that professionals should refer to when dealing with corrosion control in the context mentioned in the question.