The objective of this research project was to define pipeline conditions where use of the 100 mV polarization criterion may be conducive to possible SCC problems. Each of the controlling conditions for the two recognized forms of SCC (high pH SCC and near neutral pH SCC) was examined, using a combination of analysis of previous research results, analysis of unpublished field data, and laboratory testing. In the original proposal, it was not planned to analyze field data but the data became available and the analysis has yielded some significant findings. The results of the literature survey, the...
The objective of this research project was to define pipeline conditions where use of the 100 mV polarization criterion may be conducive to possible SCC problems. Each of the controlling conditions for the two recognized forms of SCC (high pH SCC and near neutral pH SCC) was examined, using a combination of analysis of previous research results, analysis of unpublished field data, and laboratory testing. In the original proposal, it was not planned to analyze field data but the data became available and the analysis has yielded some significant findings. The results of the literature survey, the analysis of the soil and electrolyte data from the SCC field digs, and the testing performed in this project all indicate that cathodic protection is generally beneficial in mitigating near-neutral pH SCC. Furthermore, the only testing reported in the literature, which suggests that cathodic protection is detrimental to this form of cracking, was performed under unrealistic conditions where cathodic polarization was applied to pipe steel samples containing growing cracks, but the beneficial environmental polarization that accompanies cathodic protection was not allowed to occur. One conclusion from this current research is that it is not necessary to consider the near neutral pH form of cracking in the selection of the CP criterion.