What code relates to external cathodic protection of on-grade metallic storage tank bottoms?

The correct code that relates to external cathodic protection of on-grade metallic storage tank bottoms is RPO193. This code specifically addresses the requirements and guidelines for maintaining cathodic protection systems that are designed to prevent corrosion in metal storage tanks, particularly those that are positioned on the ground's surface. Understanding this code is crucial for professionals involved in cathodic protection, as it outlines the methods and processes necessary to ensure the integrity and longevity of these storage tanks.

RPO193 focuses on the specific considerations for underground or on-grade applications, ensuring that industry best practices are followed to mitigate corrosion risks effectively. This code helps professionals determine the appropriate cathodic protection measures and maintenance strategies needed to keep storage tanks safe from corrosion-related failures.

In contrast, the other options are not recognized codes related to this specific application. Each of those potentially serves different functions or applications in the industry, but they do not pertain to the external cathodic protection standards for on-grade metallic storage tank bottoms. Understanding the distinct roles of these codes is important for compliance and effective corrosion management in storage tank operations.