Cathodic potential (CP) criteria have been used as a recommended minimum requirement for controlling external corrosion of buried or submerged steel piping systems. In Part 1 of the three-part paper discrepant and sometimes conflicting CP criteria in global CP standards were reviewed and the correlation between CP criteria and theory was discussed. In Part 2 a correlation between steel pipe native/rest potentials vs. soil resistivity was developed and validated with laboratory and field data and its relevance to CP criteria is reported. Field and laboratory data were evaluated to understand the effectiveness of the -850 mV on- and off?potential criteria; the results are reported in this paper.