When dealing with corrosion in pipelines, there are a number of different factors to consider. In recent years, new technologies have been added to the tool kit – approaches that weren't even envisioned back in 1971, when the first pipeline corrosion regulations came out.
The causes of pipeline corrosion can include soil conditions, water inside a pipeline, external damage, microbes, impurities in the pipeline and others. There is more data available than ever before to analyze these issues,contributing to the innovative corrosion control methods coming into use. However, one of the biggest concerns facing pipeline builders and operators is an aging infrastructure.
North American Oil & Gas Pipelines noted that there are a large number of pipelines built in the 1950s that are still in service. Dirk van Oostendorp, director of engineering services for Corrpro, was quoted as saying "Typically, when you design and build a pipeline, you design it to last for 25 years. Many of our pipelines are well beyond their design life." Since the cost of replacing them all would be astronomical, Oostendorp said many operators are focusing on "geriatric rehabilitation" to keep lines functioning.
Technology to the rescue
What are the technologies being used to keep corrosion in check? Here are a few of the most common strategies.
- Coatings – These can be employed both internally and externally, protecting the pipeline against both the environment outside and the material flowing through its interior. According to the Canadian Energy Pipeline Association, the most common coating is epoxy, a paint-like substance that seals the surface of the pipeline.
- Cathodic protection systems – These use anodes, rectifiers and DC currents to detour the corrosion to a replaceable anode, reducing the damage to the pipeline itself.
- AC mitigation – This is a strategy developed for a very specific situation. When you have pipelines built in parallel to overhead power lines, methods such as fault shielding, gradient control mats, grounding systems and gradient control wire help protect the pipeline from AC interference.
- Microbial control – Non-destructive evaluation is used in instances of microbially influenced corrosion, and mitigation methods are decided on a case-by-case basis once the particular microorganisms are known.
- Repairing external damage – Third-party strikes or installation errors can cause damage to the pipeline coating, sometimes as small as pin pricks or microscopic scratches. Stress corrosion cracking is another problem, caused by a combination of environmental and material factors. Experimental treatments for these include new technologies that do a better job of seeping into all the various cracks and fissures, forming a new, more effective coating layer.
- Other methods of corrosion control – These include inline inspection, ultrasonic testing, large wire brushes that scrape the pipeline interior, application of corrosion inhibitors, radiographic testing, hydrotesting, visual surveillance (including both aerial inspections and walking pipeline right-of-ways) and other means.
What the future holds
Alasdair Stoddart, director of pipeline integrity management at Corrpro, says he thinks pipeline operators will be looking to service providers in the next few years to be stronger partners in the fight against corrosion.
"We're looking to become an integrity partner with our customers, being more of a full suite provider from pipeline commissioning to monitoring thereafter," he said. "Asset owners are looking for integrity companies to provide more guidance. Let the experts do the role they were designed to do more effectively."