It is extremely important to maintain the integrity of on-grade metallic storage tanks for both economic and environmental reasons. The proper design, installation, and maintenance of cathodic protection systems can help maintain this integrity and increase the useful service life of on-grade metallic storage tanks.
The purpose of this recommended practice is to outline practices and procedures for providing cathodic protection to the steel bottoms of on-grade storage tanks that are in contact with the electrolyte.
Recommendations are included for both galvanic anode systems and impressed current systems.
Design criteria are included for the upgrade of existing tanks as well as for newly constructed tanks. This standard should be used by people planning to install new on-grade metallic storage tanks, upgrade cathodic protection on existing tanks, or install new cathodic protection on existing tanks.
This NACE International standard recommended practice was prepared by NACE Task Group
T-1 0A-20, a component of NACE Unit Committee T-lOA on Cathodic Protection, and is issued under the auspices of NACE Group Committee T-10 on Underground Corrosion Control. The task group was composed of corrosion engineers, technicians, and other people experienced in the design, installation, and maintenance of cathodic protection systems for on-grade metallic storage tank bottoms.
1.1 This recommended practice presents guidelines for the design, installation, and maintenance of cathodic protection for the exterior bottoms of on-grade metallic storage tanks. Cathodic protection can be installed to protect new or existing tanks, but cannot protect metallic surfaces that are not in contact with the electrolyte.
1.2 Tanks considered in this recommended practice can be welded, bolted, or riveted. For the purpose of this recommended practice, field- and shop-fabricated tanks are discussed together.
1.3 It is understood in this document that cathodic protection may be used alone or in conjunction with protective coatings.
1.4 All cathodic protection systems should be installed with the intent of conducting uninterrupted, safe operations. When cathodic protection is applied, it should be operated continuously to maintain polarization.
1.5 The criteria for cathodic protection are based upon current industry standards.
1.6 Corrosion control must be a consideration during the design of on-grade metallic storage tanks.
Historical document 1993