Impressed Current Cathodic Protection of Internal Submerged Surfaces of Carbon Steel Water Storage Tanks
|Publication Date:||31 October 2018|
This standard presents recommended practices for applying ICCP 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 (natural waters). These tanks may be provided with an interior barrier coating. Appendix A (nonmandatory) provides guidance for the use of impressed current cathodic protection for the internal surfaces of tanks and vessels containing other waters.
It is recognized that galvanic anode systems can, at times, be used for cathodic protection of the internal surfaces of water storage tanks;(1) however, this standard addresses only impressed current systems
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.
Cathodic protection, as described in this standard, may be used alone to control corrosion of submerged steel surfaces or used in conjunction with protective coatings compatible with cathodic protection. Cathodic protection cannot protect surfaces that are not submerged. Non-submerged surfaces must be protected by coatings alone. Cathodic protection does not reverse structural damage already caused by corrosion.
Cathodic protection may be installed to control corrosion in both newly constructed and existing tanks. When installing cathodic protection on existing tanks, it is not necessary to prepare the surfaces to be protected; however, it may be necessary to drain the tank during installation.
It is recognized that the tanks under consideration are often associated with potable water and fire protection systems, which may be subject to public health and safety regulations. This standard should not infringe upon those regulations. Proper disinfection of the tanks may be required after installation. Any applicable regulations such as those from the U.S. Environmental Protection Agency (EPA)(2) and ANSI)(3)/NSF(4)-612 should be checked. In the United States, all materials in contact with potable water or exposed to the interior of potable water tanks must be classified in accordance with ANSI/NSF-61. In other countries, ensure conformance with applicable standards and regulations.
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 and cathodic protection for water storage tanks. Such persons may be registered professional engineers or persons certified by NACE International as Cathodic Protection or Corrosion Specialists, if their professional activities include suitable experience in corrosion control and cathodic protection.
This standard may not be applicable in all situations. The responsible corrosion engineer may consider alternate corrosion control methods.