scope:

General

This standard presents standard practices for using galvanic anodes to apply CP to the internal submerged surfaces of steel tanks used for the storage of potable and reclaimed water, drinking water, irrigation water, and fire protection water. Appendix A (nonmandatory) provides guidance for the use of CP for the internal surfaces of tanks and vessels containing other waters.

Impressed current CP systems are used extensively for the internal surfaces of water storage tanks; however, this standard addresses only galvanic anode CP systems. For a description of impressed current CP systems, refer to NACE SP0388.¹

The ground level and elevated storage tanks considered in this standard are of welded, bolted, or riveted-steel construction, and include many shapes and sizes. The guidance and recommendations in this standard may be considered by the corrosion engineer for application to similar buried or vaulted tanks or tanks of other construction, where appropriate.

CP as described in this standard may be used alone to control corrosion of submerged steel surfaces or may be used as a complement to the protection provided by protective coatings compatible with CP.² CP cannot protect surfaces that are not submerged. Non-submerged surfaces should be protected by coatings alone. CP does not reverse metal loss already caused by corrosion.

CP may be installed to control corrosion in both newly constructed and existing tanks. When installing CP on existing tanks, it is not necessary to recoat the surfaces to be protected, but it may be necessary to drain the tank during installation.

Tanks under consideration for application of CP are often associated with potable water and fire protection systems that may be subject to public health and safety regulations.³ This standard shall not infringe on those regulations. Proper disinfection of the tanks may be required after installation.

The provisions of this standard should be applied under the direction of a competent corrosion engineer. The term "corrosion engineer," as used in this standard, refers to a person who, by reason of knowledge of the physical sciences and the principles of engineering and mathematics as acquired by professional education and related practical experience, is qualified to practice corrosion control, including CP, for water storage tanks. Such persons may be Registered Professional Engineers or persons recognized as being qualified or certified as Corrosion Specialists or CP Specialists by NACE, if their professional activities include suitable experience in corrosion control and CP.

This standard may not be applicable in all situations. The responsible corrosion engineer may consider alternate corrosion control methods.