# Office of Pipeline Safety — Pipeline Safety Interpretation - **operation:** document - **citation:** PI-91-013 - **title:** Office of Pipeline Safety — Pipeline Safety Interpretation - **source type:** guidance - **agency:** Pipeline and Hazardous Materials Safety Administration - **status:** guidance - **official:** true - **published on:** 1991-05-23 - **effective on:** Not available - **summary:** PI-91-013 response to Office of Pipeline Safety concerning 192.479, 192.481. - **machine formats:** - **json:** https://regulus.evalyn.ai/document/phmsa-interpretation-pi-91-013.json - **markdown:** https://regulus.evalyn.ai/document/phmsa-interpretation-pi-91-013.md - **app url:** https://regulus.evalyn.ai/document/phmsa-interpretation-pi-91-013 - **source url:** https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1991/PI91013.pdf **body:** <<>> Mr. Walter Kelly Director Office of Pipeline Safety 175 Aurora Avenue St. Paul, MN 55103 Dear Mr. Kelly: I am responding to Mr. William Barbeau's letter of January 9, 1991. He asked us to comment on his position that passive surface oxidation, or surface rust, comes within the meaning of "atmospheric corrosion" under §§192.479 and 192.481. Surface rust or passive surface oxidation caused by atmospheric corrosion would subject the pipeline to the requirements of §192.479(b) if the corrosion is deteriorating the pipeline, such as pitting. Section 192.479(a) requires that a pipeline be cleaned and either coated or jacketed with a material suitable for the prevention of atmospheric corrosion unless it can be shown that a corrosive atmosphere does not exist; e.g., showing that passive surface oxidation does not deteriorate the pipeline. In any event, §192.481 requires that pipelines that are exposed to the atmosphere be monitored for atmospheric corrosion. With regard to the assertions by two operators that passive film oxidation protects the pipeline, studies have shown that passive film oxidation inhibits atmospheric corrosion. Therefore, the rate of corrosion could be slowed to the point that the corrosion is not deteriorating the pipeline. Please let me know if you need further assistance in this matter. Sincerely, George W. Tenley, Jr Associate Administrator for Pipeline Safety DB C:\WP51\INTERPRT\192\479\91-05-23 1 - **truncated:** false - **body characters:** 1453