What is stress corrosion cracking and why does it occur?
SCC in pipelines is a type of environmentally assisted cracking. SCC results from the formation of cracks due to various factors in combination with the environment surrounding the pipeline that together reduces the pressure-carrying capability of the pipe. When a pipeline under higher pressures (stress) comes into contact with water due to coating failure, the minerals, ions, and gases in the water at the pipe surface create corrosion that attacks the pipe. SCC tends to propagate as crack clusters or “colonies” as pipeline stress opens cracks that are subject to corrosion, which are then corroded further, weakening the pipeline metal by further cracking. There are 2 types of SCC of concern to the pipeline industry: • High pH SCC – typically occurs within 15 miles downstream of pipeline compressor or pump stations where temperatures of the transported medium may exceed 100 °F. Along with the elevated temperatures, a groundwater/carbonate/bicarbonate solution (high pH) would have to be
