Pipelines are the major arteries of the energy sector, transporting oil, gas and other crucial products that fuel the American economy. Keeping these arteries healthy and free of defects is critical as a failed pipeline can lead to significant property damage, injury, and death.
Corrosion is one of the leading causes of pipeline incidents with the U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA) data showing 18 percent of pipeline incidents on average were caused by corrosion between 1998 and 2017.
“Corrosion is considered a time-dependent threat which means it grows or worsens with time if left unmitigated. As a result, early detection and mitigation are necessary to minimize the impact of corrosion,” says PHMSA.
Some estimate that corrosion costs the oil and gas industry more than $1 billion annually.
Corrosionpedia, the online hub for corrosion industry professionals, says that pipeline corrosion is a natural deterioration and destruction of pipe material and essential properties due to electrochemical and other ingredient reactions of pipeline materials with their environment.
Pipeline corrosion can occur on the inside as well as the outside surfaces and occurs naturally due to the gradual and continuous environmental attack on pipe materials.
“This reaction causes the iron in the steel pipe or other pipeline appurtenances to oxidize (rust),” says PHMSA. Both metal and non-metal pipes, pipe joints, welds, and surface coatings can be affected by corrosion.
“Corrosion changes the structure, essential properties and chemical composition of materials,” says Corrosionpedia.
Environmental conditions that can cause corrosion, according to Corrosionpedia, include:
PHMSA breaks down pipeline corrosion by where and/or how it occurs:
Corrosionpedia says it helps to know the causative agent that is creating corrosion to determine the type of protection needed.
“In most cases, corrosion as an electrochemical reaction begins with a causative environmental agent that sets up an anode and cathode. The corrosion cell is generated through electrolysis in the presence of electrolyte, oxygen cell or through galvanic action, in the event of dissimilar metals in contact,” says Corrosionpedia.
PHMSA says that corrosion can result in gradual and usually localized metal loss resulting in reduction of the wall thickness of the pipe.
If not prevented or mitigated effectively, the result can be:
What happens next could be either leakage from the pipe (typical) or an open break failure (rupture) of the pipe (less typical) unless the corrosion is repaired, the affected pipe section is replaced, or the operating pressure of the pipeline is reduced.
Where corrosion involves a longitudinal seam of a pipe or cracks in the pipe, the likelihood of a break or rupture increases. Stress corrosion cracking and selective seam corrosion are in this category.
Hydrogen cracking or embrittlement can also weaken a pipeline when isolated points of elevated steel hardness exist - this is a rare material defect present in some older types of pipes.
If left untreated, PHMSA says corrosion can weaken the pipe where the corrosion occurs, and make the pipe more susceptible to overpressure events, earth movement, and other external stresses.
The prevention and mitigation of pipeline corrosion is built on a three-prong approach:
The periodic inspections for pipeline corrosion can be carried out via:
GeoCorr uses pipeline inspection pigs to perform magnetic flux leakage (MFL) inspections which can not only detect corrosion and pitting but can also find other general metal loss anomalies.
At GeoCorr, our analysis can provide preliminary reports in under 30 days and standard final reports in less than 60 days. Contact GeoCorr today to find out how our in-house experienced team can help you improve your pipeline safety with an inline MFL inspection.