What is the required negative polarized potential with cathodic protection applied, according to SP0169?

According to the NACE SP0169 standard, the required negative polarized potential for effective cathodic protection on buried or submerged metallic structures is typically -850 mV. This threshold is determined to ensure that the structure is adequately protected from corrosion due to electrochemical processes.

Achieving this potential indicates that the structure has been sufficiently polarized and is undergoing effective cathodic protection. It represents a balance between providing enough protection to prevent corrosion while avoiding excessive polarization, which could potentially lead to issues like hydrogen embrittlement in certain materials.

Other potential values listed are not recognized as the standardized target for cathodic protection under SP0169. -750 mV, while closer to the mark, does not provide the necessary assurance of corrosion prevention. -900 mV might seem adequate, but it typically exceeds the threshold and can present risks. -1200 mV indicates a level of polarization that is generally considered excessive for most applications, and could lead to complications. Thus, -850 mV stands out as the ideal target for achieving effective cathodic protection.