What ASTSWMO UST Task Force Found
The ASTSWMO UST Task Force solicited information for fiscal year 2012 from all 50 states, five territories, and the District of Columbia in an effort to determine the violations most often encountered during UST compliance inspections. Responses were received from 35 states and territories, covering nearly 59,000 UST inspections and more than 37,000 violations.
A review of the data identified corrosion protection as one of the top five inspection violation issues. According to the report, in reference to corrosion protection, there were 2,811 total violations, 49 percent of which were for failure to perform the 3-year CP test, and 20 percent for failure to maintain and operate the CP system properly. Another 17 percent of the violations were for unprotected metal in contact with soil or water, and 7 percent each for failure to complete the 60-day CP operational test and failure to maintain records.
Some Facts About Corrosion
“Corrosion” can be defined as the degradation of a material because of a reaction with its environment.
According to the a study initiated by NACE International (formerly the National Association of Corrosion Engineers), which was funded by the U.S. Federal Highway Administration, the annual cost of corrosion is $276 billion and affects every industry sector in the United States. (Note: The study was done in 2002 but is still considered influential in the field).
Corrosive chemicals are most often thought of as being liquids. But they can also be solids, such as granules or powders. Corrosive gases or mists are often released from concentrated corrosive liquids.
Because metals are the most used type of structural materials, such as tanks, we will focus on the corrosion of metals. According to NASA’s Corrosion Technology Laboratory, most corrosion of metals is electrochemical in nature.
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Check for Corrosion in Your AST
Simple AST checks you can perform to prevent corrosion include:
- Have the tank either elevated with the underside in contact only with tank supports and/or on a concrete pad designed to prevent water accumulation under the tank floor.
- Make sure the tank is cathodically protected and internally lined according to American Petroleum Institute (API) Standard 652 (Lining of AST Petroleum Storage Tank Bottoms) and internally inspected according to API Standard 653 (Tank Inspection, Repair, Alteration, and Reconstruction).
- During visual inspections, note the general appearance of paint on the shell, roof, ladder, and structural members.
- Is rusting or pitting occurring on any of the above?
If yes, explain where and if repairs are needed immediately.
- Are all insulating flange washers and sleeves in place?
If missing, cracked, or broken, explain where and repairs needed.
- Are all ground and/or anode straps in place?
If missing or damaged, indicate location on a drawing and explain repairs needed.
- Make sure that the secondary containment system is free of tank product or other liquids/debris (e.g., rainwater, snowmelt, dirt, leaves, trash, stored materials).
- Make sure that concrete surfaces and the ground are free from any evidence of spills or leaks.
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Check for Corrosion in Your UST
Under current UST regulations, new tanks must be constructed of coated and cathodically protected steel, fiberglass or reinforced plastic, or steel clad with fiberglass. New piping must be made of coated and cathodically protected steel or of fiberglass. All cathodic protection systems must be tested within 6 months of installation and, after that, at least every 3 years.
Note: The EPA released final amendments to UST regulations in late June. The UST amendments are effective 90 days after publication in the Federal Register.
The final amendments to the UST regulations replace the option of constructing new tanks from a steel-fiberglass-reinforced-composite with the option of constructing the tank of steel that is clad or jacketed with a non-corrodible material.
In addition, under the final amendments to UST regulations, UST owners and operators must permanently close tanks that use internal lining as the sole method of corrosion protection if the internal lining fails the periodic inspection and cannot be repaired according to a code of practice. The 1988 regulations allowed lining as an upgrade option to extend the life of some tanks. While linings extended the life of many tanks, the EPA did not consider this a permanent solution. As the tank linings fail, these older tanks must be taken out of service to prevent releases to the environment. This requirement is effective immediately upon the effective date of the amendments (i.e., 90 days after publication in the Federal Register).
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It would help to provide some information about what is meant by cathodic protection. The following is taken from EPA’s website:
Cathodic protection is one option for protecting an underground storage tank (UST) from corrosion. There are two types of systems for cathodic protection:
Sacrificial anodes can be attached to a coated1 steel UST for corrosion protection. Sacrificial anodes are pieces of metal more electrically active than the steel UST. Because these anodes are more active, the corrosive current will exit from them rather than the UST. Thus, the UST is protected while the attached anode is sacrificed. Depleted anodes must be replaced for continued corrosion protection of the UST.
An impressed current system uses a rectifier to convert alternating current to direct current. This current is sent through an insulated wire to the anodes, which are special metal bars buried in the soil near the UST. The current then flows through the soil to the UST system and returns to the rectifier through an insulated wire attached to the UST. The UST system is protected because the current going to the UST system overcomes the corrosion-causing current normally flowing away from it.
Federal regulations require that the cathodic protection systems installed at UST sites (field-installed) be designed by a corrosion expert.
The system must be tested by a qualified cathodic protection tester within six months of installation and at least every three years thereafter. In addition, cathodic protection systems must be tested within six months of any repair to any cathodically protected UST system. You will need to keep the results of the last two tests to prove that the cathodic protection is working. In addition, you must inspect an impressed current system every 60 days to verify that the system is operating. Keep results of your last three 60-day inspections to prove that the impressed current system is on and operating properly.