A method to evaluate the corrosive environment of annular spaces within casings of natural
gas transmission pipelines using commercially available, “off the shelf” equipment has been
devised and implemented. Three separate locations were selected for test monitoring of
corrosion rates on steel carrier pipelines operating within these environments. The locations
were monitored for 22-26 months and average corrosion rates were established for a variety of
representative conditions. Test results confirmed the initial hypothesis that cased pipeline
segments exist in relatively benign environments as long as cathodic protection/coating
systems and electrical isolation status between carrier and casing are maintained. These
results lend further credence to the position that cased segments are inherently safer than
uncased segments due to the extra layer of protection from third party damage which remains
the most significant threat to pipeline integrity.
Keywords: corrosion rate, casings, cased pipeline segments, annular space, direct
assessment, high consequence areas, natural gas transmission pipeline, external corrosion
direct assessment, ECDA, electrical resistance (ER) corrosion rate probes.