Materials Performance Supplements

TANK 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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24 MAY 2018 W W W.MATERIALSPERFORMANCE.COM TANK CORROSION CONTROL SUPPLEMENT TO MP Tank Protection Articles its sides, bottom, and at any penetrations. It must allow for visual inspection and access to the contained components or be period- ically monitored for leaks from the dis- penser system. 5 The docket for the UST regulation is EPA-HQ-UST-2011-0301-0450 and can be accessed at Corrosion Protection for USTs: An Overview According to the EPA, 2 unprotected underground metal components of the UST system—tanks, piping, and metal compo- nents such as f lexible connectors, swing joints, and turbines—can corrode, and holes caused by corrosion can lead to prod- uct releases. Corrosion can begin as pitting on th e m et al sur fa c e, an d h o l e s m ay develop as corrosion continues and pits become deeper. Over time, even a small corrosion hole can release a significant amount of product. All metal UST system components that are in contact with the ground and routinely contain product must be protected from corrosion. The two com- mon methods used for protecting metal components from corrosion are isolating the metal component from the corrosive environment and CP. Tank Linings A structurally sound tank interior may be lined with a thick layer of noncorrodible material, as long as the lining material and application method comply with applica- bl e in du str y c o d e s. The lining used must al so m eet th e sam e federal requirements as for repaired tanks (40 CFR 280.33). Flexi- ble inner liners (blad- ders) that fit inside a tank do not meet the tank int erior linin g requirements. Tanks using only an interior lining for corrosion protection must pass an internal inspection within 10 years and every five years after t h a t t o e n su re t h e tank and lining are sound. Records of these inspection results should be kept. Cathodic Protection A CP system—either a sacrificial anode or impressed current system—is another option for protecting USTs from corrosion. Sacrificial anodes can be attached to a coated steel UST for corrosion protection; however, the coating must be a suitable dielectric material (i.e., a coating that elec- trically isolates the UST from its environ- ment and meets applicable industry codes. An asphaltic coating is not considered a suitable dielectric coating ). Sacrificial anodes are more electrically active than the steel UST. Because these anodes are more active, the attached anode is sacrificed w hi l e th e U ST i s prot e ct ed . D e pl et ed anodes must be replaced for continued cor- rosion protection of the UST. An impressed current CP (ICCP) system uses a rectifier to convert alternating cur- rent (AC) to direct current (DC). This cur- rent is sent through an insulated wire to the anodes, which are buried in the soil near the UST. The current then f lows through the soil to the UST system and returns to the rectifier through an insulated wire attached to the UST. The UST system is pro- tected because the current going to the UST system overcomes the corrosion-causing current normally flowing away from it. Federal regulations require that the field-installed CP systems installed at UST sites be designed by a corrosion expert. Within six months of installation and at least every three years thereafter, the CP system must be tested by a qualified CP tes- ter. An ICCP system must be inspected every 60 days to verify that the system is operating. Additionally, within six months of a repair to any cathodically protected UST system, the CP system must be tested. The results of the last two tests must be kept to prove that the sacrificial CP system is working. Results of the last three 60-day inspections must be kept to verify the ICCP system is on and operating properly. Tank Lining Combined with Cathodic Protection Applying both an interior lining and CP is another option for upgrading existing tanks. Combining the two corrosion protec- tion systems has several advantages: the USTs receive greater corrosion protection and the condition of the interior lining does not require periodic inspection . W hile these advantages can amount to significant cost savings over using an interior lining alone, the CP system must periodically be tested and inspected to ensure it is working properly. Records of these tests and inspec- tions must be kept. Source: U.S . Environmental Protection Agency, web site: References 1 " Impl em ent ation Tim e Fram e s for 2015 Underground Storage Tank Requirements," EPA, f i l e s/2015-09/do cum ents/impl em entbro- chure091515.pdf (March 29, 2018). 2 "Underground Storage Tanks (USTs)," EPA, (March 29, 2018). 3 Underground Storage Tanks (USTs), Release Prevention for Underground Storage Tanks (USTs), "Corrosion Protection," EPA, https:// ground-storage-tanks-usts (March 29, 2018). 4 Underground Storage Tanks (USTs) "Revis- ing Underground Storage Tank Regulations- Revisions to Existing Requirements and New Requirements for Secondar y Containment and Operator Training," EPA, https://www. e p a . g o v / u st / re v i si n g - u n d e rg r o u n d - st o r - age-tank-regulations-revisions-existing-re- quirements-and-new (March 29, 2018). 5 Underground Storage Tanks (USTs), Sec- ondary Containment and Under-Dispenser C ont ainm ent —2015 Requirem ent s, EPA, https://www.epa .gov/ust/secondar y-con- t a i n m e n t - a n d - u n d e r - di sp e n s e r - c o n t a i n - ment-2015-requirements (March 29, 2018). The EPA made several revisions to the 1988 UST regulation and the 1988 state program approval (SPA) regulation to help ensure all USTs in the United States meet the same release protection standards.

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