Task Order #1: External Corrosion of Line Pipe Steels

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• Damage Condition Assessment
• External Corrosion
• Stress Corrosion Cracking

Main Objective

The US Department of Transportation (DOT), Pipeline and Hazardous Materials Safety Administration (PHMSA), has a requirement to provide technical expertise as it implements its program of research and standardization activities, focusing on pipeline materials, inspection processes, and measures of materials performance and reliability to support PHMSA efforts to maintain and ensure the integrity of natural gas and hazardous liquid pipelines. The Pipeline Infrastructure Protection to Enhance Safety and Security Act (H.R. 3609) provides NIST and PHMSA with an opportunity for increased coordination and collaboration on natural gas and hazardous liquid pipeline facility research, development, demonstration and standardization.

Year 2 Objective:
The objective of the proposed research is to provide critical standards and data for improving pipeline integrity and speeding the evaluation of new pipeline designs or failures. This objectivewill be accomplished by working with PHMSA and the pipeline community to improve and update pipeline corrosion standards. To update such standards requires an assessment of the environmental and electrochemical conditions that cause corrosion damage that could lead to failures in modern pipeline materials, and the development of databases of corrosion damage mechanisms and kinetics for steels in different types of soils.

Public Abstract

PHMSA will seek technical expert services from NIST to assist PHMSA in evaluating emerging technologies and standards. This technical expertise will respond to research and standardization activities focusing on pipeline materials, inspection processes, and measures of materials performance for enhancing pipeline reliability.

Total project proposal = $500,000.00 ($250,000 this project and $250,000 for Project No 158, "Fatigue Fracture and Crack Arrest in High-Strength Pipeline Steels")

Year 2 Background:
External corrosion, stress corrosion cracking, and hydrogen stress cracking are the main mechanisms by which the external environments and corrosion can cause failure of pipelines. External corrosion results from the breakdown of coatings and cathodic protection systems. Typically, pit-like defects form and grow until the stress intensity exceeds that for critical fracture or initiation of fatigue or stress corrosion cracking. External Corrosion � The pipeline industry has found that the 0.4 mm/yr (0.016 in/yr) allowance
for pitting specified in existing standards is overly conservative for most pipeline environments. This pitting allowance was determined largely on the NBS (now NIST) underground corrosion experiments conducted between 1910 and 1955 and published in 1957 [1,2]. Since the alloys, coatings, and protection systems used in these studies are not representative of current systems and the corrosion rates and mechanisms observed on the coupons are not representative of the long term performance of existing early generation pipelines, industry has found this allowance to be overly conservative for most environments and not conservative enough in some environments. The objective of this study is to determine if evaluation of existing data combined with modern laboratory corrosion measurement methods, statistical analysis techniques, and modeling methods can provide more appropriate guidelines for the external corrosion allowance. Corrosion Related Failure Investigations - In addition to performing the above work, NIST will conduct investigations of corrosion related pipeline failures as requested by PHMSA for the purpose of providing technical support to PHMSA and gaining knowledge that will compliment this research.