USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #PI-91-013 ([Office of Pipeline Safety] [Walter Kelly])

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date:

Company Name: Office of Pipeline Safety

Individual Name: Walter Kelly

Location State: MN Country: US

View the Interpretation Document

Response text:

Mr. Walter Kelly


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.


George W. Tenley, Jr

Associate Administrator

for Pipeline Safety

Regulation Sections

Section Subject
192.479 Atmospheric corrosion control: General
192.481 Atmospheric corrosion control: Monitoring