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Fact Sheet: Selective Seam Corrosion (SSC)

Quick Facts:

  • SSC is a form of corrosion that tends to affect pipe manufactured prior to 1970 using low-frequency electric resistance welding (LR-ERW) or electric flash welding (EFW) processes.
  • SSC is a localized corrosion attack along the weld bondline of ERW and EFW pipe, that leads to the development of a wedge shaped groove that is often filled with corrosion products.
  • SSC is affected primarily by the degree of exposure to corrosive conditions such as poor or absent pipe coatings and ineffective cathodic protection.
  • Improved technologies have led to better prevention, monitoring, detection, and mitigation of pipeline SSC.
  • New pipeline Integrity Management regulations promote early identification and repair of SSC.
  • Refer to other Fact Sheets for specific discussion of issues related to corrosion in general, external corrosion, internal corrosion, and stress corrosion cracking.

What is Selective Seam Corrosion and why does it occur?

SSC is a localized corrosion attack along the bond line of low-frequency electric resistance welding (LR-ERW) and electric flash welding (EFW) piping, that leads to the development of a wedge shaped groove that is often filled with corrosion products. LR‑ERW or EFW pipe manufacturing processes first came into use in the 1920s. Both types of pipe are manufactured by forming steel plates into round cylinders and then joining the longitudinal edges through a welding process. Due to technology and quality control issues with some of the pipe manufactured prior to 1970, the weld bondline may be susceptible to corrosion processes. This is particularly true if the pipeline has the following conditions present:

  • Exposure to corrosive conditions due to poor or absent coating
  • Ineffective cathodic protection
  • The presence of non-metallic inclusions in the weld bondline region (e.g., contaminants present during the manufacturing process).

SSC is generally not considered to be a concern with pipe manufactured subsequent to 1970 due to the use of cleaner steels having greatly reduced sulfur contents and the replacement of low frequency welding equipment with high frequency equipment in the manufacturing process.

What are the risks from Selective Seam Corrosion?

SSC results in a long, sharp V-notch or crevice-like corrosion area centered on the bondline of the pipe’s longitudinal weld. The corrosion may reach a critical depth and length combination that can result in a pipeline failure unless the SSC is repaired, the affected pipeline section is replaced, or the operating pressure of the pipeline is reduced.

Pipeline SSC creates weaknesses at points in the pipe, which in turn makes the pipe more susceptible to third party damage, overpressure events, etc. (i.e., SSC doesn't necessarily need to cause the leak or rupture itself to increase risk).

Pipeline failure rates from Selective Seam Corrosion

The failure rate due to SSC is low, approximately 1 percent of the incidents reported to OPS, however, it is a risk that must be addressed as it can manifest itself wherever the right combination of factors exist.

What is being done to prevent/mitigate Selective Seam Corrosion?

  • Research into the causes and prevention of SSC are ongoing within the industry. It has been found that cleaning and preparing pipe surfaces through shot-peening and then applying special coatings (fusion bonded epoxy) will protect the pipe from the occurrence of SSC.
  • Operators use cathodic protection systems to protect pipelines from corrosion. Annual surveys of the effectiveness of their cathodic protection reveal areas where coating may be disbonded from the pipeline, allowing corrosion solutions to come in contact with portions of the pipe surface and potentially creating conditions conducive to SSC.
  • The Office of Pipeline Safety has implemented new Pipeline Integrity Management (“IM”) regulations that require all pipeline operators to inspect and assess all of their pipelines that could affect areas of high consequence such as populated areas and environmentally sensitive areas. The operators are required to inspect and assess their pipelines for integrity issues, such as SSC, and repair or replace affected pipe. Inspection techniques may include:
    • Inline inspection tools – “smart pigs”
    • Hydrostatic pressure tests
    • Direct assessment
  • By implementing the requirements of the regulation and through responsible maintenance programs, pipeline operators continuously inspect their pipelines for indications of SSC.

Selective Seam Corrosion : What more can be done?

  • Public : Be aware of pipelines located near you. Be observant for signs of pipeline damage, leakage, or security concerns. Report any concerns you have regarding pipeline safety to the pipeline operator immediately. Always respect the pipeline right-of-way. Do not dig or build on a pipeline right-of-way without first contacting the pipeline operator or your state one-call center.
  • Industry : Pipeline operators and industry stakeholders can continue to develop and implement improved SSC detection and prevention technologies. Operators must continue to implement SSC protection effectively and strengthen pipeline integrity management programs. Operators must mitigate the effects of SSC when it is detected.
  • Regulators : OPS and state regulators must continue to inspect pipeline operators to ensure they effectively implement required integrity management programs, including protection for SSC, to ensure that risks to pipelines are identified and mitigated at the earliest possible time. Better coordination is needed between local permitting agencies and pipeline operators to facilitate expeditious granting of permits when public safety is potentially threatened.

Selective Seam Corrosion: Where Can I Learn More?

Date of Revision: 12012011