According to a 2014 report by the Association of State and Territorial Solid Waste Management Officials’ (ASTSWMO) Underground Storage Tank (UST) Task Force, one of the most common violations found during UST inspections involved deficiencies in corrosion protection.

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 Corrosion Protection (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, this article focuses on the corrosion of metals. According to NASA’s Corrosion Technology Laboratory, most corrosion of metals is electrochemical in nature.

Check for Corrosion in Your AST

Simple AST checks you can perform to prevent corrosion include:

 

  1. 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.

 

  1. 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).

 

  1. During visual inspections, note the general appearance of paint on the shell, roof, ladder, and structural members.

 

  1. Is rusting or pitting occurring on any of the above? If yes, explain where and if repairs are needed immediately.

 

  1. Are all insulating flange washers and sleeves in place? If missing, cracked, or broken, explain where and repairs needed.

 

  1. Are all ground and/or anode straps in place? If missing or damaged, indicate location on a drawing and explain repairs needed.

 

  1. 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).

 

  1. Make sure that concrete surfaces and the ground are free from any evidence of spills or leaks.

 

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).

 

Cathodic Protection

 

Cathodic protection uses direct electrical current to mitigate corrosion.

 

There are two types of systems for cathodic protection:

 

  • Sacrificial anodes, which can be attached to a coated 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. Therefore, the UST is protected while the attached anode is sacrificed. Depleted anodes must be replaced for continued corrosion protection of the tank.

 

  • Impressed current systems use rectifiers 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.

 

Maintenance and Testing Tips

 

General Tip 1: Cathodic protection systems require periodic maintenance and testing to ensure that they are functioning properly. Some checks require only visual observations. Others are more involved. For detailed information about cathodic protection operation and maintenance, see the NACE International SP0169 standard (Control of External Corrosion on Underground or Submerged Metallic Piping Systems). Another NACE standard for USTs is SP0285 (Corrosion Control of Underground Storage Tank Systems by Cathodic Protection). Both standards can be purchased on the NACE website.

 

Tip 2: Ensure that aboveground equipment such as rectifier cabinets, junction boxes, and test stations are screened and that there are no unused or unsealed openings that would allow insects such as wasps and spiders to access the equipment.

 

Tip 3: Allow only trained and qualified staff to perform the required maintenance and testing on cathodic protection systems.

 

Tip 4: Inspections for sacrificial anode systems:

 

  • Monthly/bimonthly: Inspect exposed system components on a monthly basis to ensure that equipment is intact. Look for damage to test stations or junction boxes, and open them to verify that connections are intact. Clean out any debris found, and schedule repairs if needed. (Note: If monthly checks are repeatedly acceptable, you can go to a bimonthly schedule.)
  • Detailed yearly inspections and testing must be performed by qualified personnel, and the records should be reviewed by a qualified corrosion professional. Make or schedule repairs as recommended by the corrosion specialist.
  • Maintain yearly inspection records along with recommendations and actions taken.

 

Tip 5: Procedures for impressed current systems:

 

  • For safety of personnel, make sure the cabinet of the rectifier is grounded per the National Electric Code (NEC) and local standards. Train personnel to verify the case is grounded and not energized before taking hold of it.
  • Padlock rectifiers and junction boxes prevent unauthorized tampering.
  • Inspect the system on a monthly basis to:
  • Verify that the rectifier is energized and no unauthorized adjustments have been made.
  • Verify that the rectifier tap settings are in the positions recorded on the last inspection sheet.
  • Verify that there is DC voltage and current output.
  • Look for scorch marks and indications of excess heat.
  • Look for damage to test stations and/or junction boxes. Open them to verify that connections are intact.
  • Clean out any debris found in rectifier cabinets, test stations, junction boxes, and bond boxes.
  • Make or schedule repairs.
  • Note: If monthly checks are repeatedly acceptable, you can move to a bimonthly schedule. Be aware, however, of rectifiers losing power due to lightning or other power interruptions.
  • Detailed yearly inspections and testing must be performed by qualified personnel, and the records should be reviewed by a qualified corrosion professional. Make or schedule repairs as recommended by the corrosion specialist.
  • Maintain yearly inspection records along with recommendations and actions taken.

 

Tip 6: For USTs, the EPA requires that all cathodic protection systems be tested within 6 months of installation and every 3 years thereafter, and within 6 months of a repair according to a nationally recognized association code practice. UST systems with compressed current cathodic protection systems must also be inspected every 60 days to ensure equipment is running properly.

 

Tip 7: For USTs, the EPA requires that records related to corrosion be kept until the UST is closed and 3 years after.

 

For more information or assistance with your Environmental and Health & Safety regulatory compliance needs, contact Ralph Carito at Total Environmental & Safety, LLC (Total) at rcarito@TotalEnviron.com or 908-442-8599.