Cathodic protection for USTs: protecting underground storage tank (UST) systems from corrosion 2005 |
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Cathodic Protection for USTs WHAT IS IT? Cathodic protection shields steel UST systems from corrosion that causes deterioration and potential failure of the UST. There are two types of cathodic protection systems: 1. Galvanic Systems (Sacrificial Anodes) 2. Impressed (Induced) Current Systems WILL YOU BE IN COMPLIANCE? Adding cathodic protection along with spill and overfill protection meets the EPA 1998 upgrade requirements (hyperlink) for existing USTs provided the UST system already has leak detection installed. Cathodic protection can only be added on tanks which are structurally sound as determined by an integrity assessment test. Contact the UST section for integrity assessment methodologies. Cathodic protection can also protect metal piping associated with the UST system. REGULATORY REQUIREMENTS & DOCUMENTATION State law requires that field-installed cathodic pro-tection systems at UST sites be designed by a cor-rosion expert. Visit the NACE website: www.nace.org or contact NACE’s customer service at (281) 228-6200 for a list of corrosion experts. TESTING & RECORD KEEPING Cathodic Protection systems must be tested by a cathodic protection tester certified by ADEQ with-in six months of UST installation or repair, and at least every three years thereafter. Call 602-771- 4316, or 1-800-234-5677, extension 771-4316 for a copy of the ADEQ-certified list of cathodic pro-tection testers. Keep the results of the last two tests to document that the cathodic protection is working. Additional requirements for an Impressed Current system: 1. Inspect an impressed current system every 60 days to verify that the system is operating. 2. Keep the results of your last three (3) 60-day inspections to document that the impressed current system is operating properly. HOW DOES CATHODIC PROTECTION WORK? A. Galvanic Systems (Sacrificial Anodes) 1. Sacrificial anodes are pieces of metal attached to the UST system that are more electrically active than the steel UST system. Because these anodes are more active, the corrosive current will exit from them rather than the UST system. Thus, the UST system is protected while the attached anode is “sacrificed.” 2. Sacrificial anodes can be attached to existing bare steel USTs or to new coated steel new USTs for a pre-engineered cathodic protection system. 3. If the sacrificial anodes are attached to a coated-steel UST, the coating must be of a suitable dielectric material. In other words, the coating will electrically isolate the UST from its environ-ment and meet applicable industry codes. An asphalt coating is not considered a suitable dielectric coating. 4. For all galvanic system, depleted anodes must be replaced for continued cathodic protection of the UST system. HOW DOES CATHODIC PROTECTION WORK? (continued) B. Impressed (induced) Current Systems 1. An impressed current cathodic protection system consists of anodes, cathodes, a rectifier and the soil. 2. The rectifier converts the alternating current to direct current. The direct current is then sent through an insulated copper wire to anodes that are buried in the soil near the UST system. 3. Typical anode materials are ceramic, high silicon cast iron, or graphite. Ceramic anodes are not consumed, whereas high silicon cast iron and graphite anodes partially dissolve each year and must be replaced over time. 4. The direct current then flows from the anode through the soil to the UST system, which acts as the cathode, and back to the rectifier through another insulated copper wire. 5. As a result of the electrochemical properties of the impressed current cathodic protection system, corrosion takes place only at the anodes and not at the UST system. 6. Depleted anodes must be replaced for continued cathodic protection of the UST system. FOR MORE INFORMATION CONTACT: Arizona Department of Environmental Quality UST & Division Support Section 1110 West Washington Street Phoenix, Arizona 85007 (602) 771-4255 toll free number: (800) 234-5677 Ext:771-4255 Website: www.azdeq.gov Impressed Current CP system checked every 60 days? Galvanic system tested within six month of installation? Galvanic system tested every three years? CP system repaired by a corrosion protection expert? Depleted anodes in galvanic system replaced? Documentation of CP system designer credentials maintained? C H E C K L I S T In the event of any discrepancy between this infor-mation and the Arizona Revised Statutes or Arizona Administrative Code, the statutes or rules shall take precedence. Publication Number: C05-02
Object Description
TITLE | Cathodic protection for USTs: protecting underground storage tank (UST) systems from corrosion |
CREATOR | Arizona Department of Environmental Quality |
SUBJECT | Underground storage tanks--Corrosion--Arizona; Cathodic protection--Arizona; |
Browse Topic |
Land and resources Water |
DESCRIPTION | This title contains one or more publications |
Language | English |
Publisher | Arizona Department of Environmental Quality |
Material Collection | State Documents |
Source Identifier | ENQ 10.4:C 17 |
Location | o68220282 |
REPOSITORY | Arizona State Library, Archives and Public Records--Law and Research Library |
Description
TITLE | Cathodic protection for USTs: protecting underground storage tank (UST) systems from corrosion 2005 |
DESCRIPTION | 2 pages (PDF version). File size: 78 KB |
TYPE |
Text |
Acquisition Note | Publication No. C05-02 |
RIGHTS MANAGEMENT | Copyright to this resource is held by the creating agency and is provided here for educational purposes only. It may not be downloaded, reproduced or distributed in any format without written permission of the creating agency. Any attempt to circumvent the access controls placed on this file is a violation of United States and international copyright laws, and is subject to criminal prosecution. |
DATE ORIGINAL | 2005 |
Time Period |
2000s (2000-2009) |
ORIGINAL FORMAT | Born Digital |
Source Identifier | ENQ 10.4:C 17 |
Location | o68220282 |
DIGITAL IDENTIFIER | cp_2005.pdf |
DIGITAL FORMAT | PDF (Portable Document Format) |
REPOSITORY | Arizona State Library, Archives and Public Records--Law and Research Library. |
File Size | 78849 Bytes |
Full Text | Cathodic Protection for USTs WHAT IS IT? Cathodic protection shields steel UST systems from corrosion that causes deterioration and potential failure of the UST. There are two types of cathodic protection systems: 1. Galvanic Systems (Sacrificial Anodes) 2. Impressed (Induced) Current Systems WILL YOU BE IN COMPLIANCE? Adding cathodic protection along with spill and overfill protection meets the EPA 1998 upgrade requirements (hyperlink) for existing USTs provided the UST system already has leak detection installed. Cathodic protection can only be added on tanks which are structurally sound as determined by an integrity assessment test. Contact the UST section for integrity assessment methodologies. Cathodic protection can also protect metal piping associated with the UST system. REGULATORY REQUIREMENTS & DOCUMENTATION State law requires that field-installed cathodic pro-tection systems at UST sites be designed by a cor-rosion expert. Visit the NACE website: www.nace.org or contact NACE’s customer service at (281) 228-6200 for a list of corrosion experts. TESTING & RECORD KEEPING Cathodic Protection systems must be tested by a cathodic protection tester certified by ADEQ with-in six months of UST installation or repair, and at least every three years thereafter. Call 602-771- 4316, or 1-800-234-5677, extension 771-4316 for a copy of the ADEQ-certified list of cathodic pro-tection testers. Keep the results of the last two tests to document that the cathodic protection is working. Additional requirements for an Impressed Current system: 1. Inspect an impressed current system every 60 days to verify that the system is operating. 2. Keep the results of your last three (3) 60-day inspections to document that the impressed current system is operating properly. HOW DOES CATHODIC PROTECTION WORK? A. Galvanic Systems (Sacrificial Anodes) 1. Sacrificial anodes are pieces of metal attached to the UST system that are more electrically active than the steel UST system. Because these anodes are more active, the corrosive current will exit from them rather than the UST system. Thus, the UST system is protected while the attached anode is “sacrificed.” 2. Sacrificial anodes can be attached to existing bare steel USTs or to new coated steel new USTs for a pre-engineered cathodic protection system. 3. If the sacrificial anodes are attached to a coated-steel UST, the coating must be of a suitable dielectric material. In other words, the coating will electrically isolate the UST from its environ-ment and meet applicable industry codes. An asphalt coating is not considered a suitable dielectric coating. 4. For all galvanic system, depleted anodes must be replaced for continued cathodic protection of the UST system. HOW DOES CATHODIC PROTECTION WORK? (continued) B. Impressed (induced) Current Systems 1. An impressed current cathodic protection system consists of anodes, cathodes, a rectifier and the soil. 2. The rectifier converts the alternating current to direct current. The direct current is then sent through an insulated copper wire to anodes that are buried in the soil near the UST system. 3. Typical anode materials are ceramic, high silicon cast iron, or graphite. Ceramic anodes are not consumed, whereas high silicon cast iron and graphite anodes partially dissolve each year and must be replaced over time. 4. The direct current then flows from the anode through the soil to the UST system, which acts as the cathode, and back to the rectifier through another insulated copper wire. 5. As a result of the electrochemical properties of the impressed current cathodic protection system, corrosion takes place only at the anodes and not at the UST system. 6. Depleted anodes must be replaced for continued cathodic protection of the UST system. FOR MORE INFORMATION CONTACT: Arizona Department of Environmental Quality UST & Division Support Section 1110 West Washington Street Phoenix, Arizona 85007 (602) 771-4255 toll free number: (800) 234-5677 Ext:771-4255 Website: www.azdeq.gov Impressed Current CP system checked every 60 days? Galvanic system tested within six month of installation? Galvanic system tested every three years? CP system repaired by a corrosion protection expert? Depleted anodes in galvanic system replaced? Documentation of CP system designer credentials maintained? C H E C K L I S T In the event of any discrepancy between this infor-mation and the Arizona Revised Statutes or Arizona Administrative Code, the statutes or rules shall take precedence. Publication Number: C05-02 |