Cathodic Protection is a corrosion mitigation practice that is used to insure the mechanical integrity of
critical steel structures such as pipelines, storage tanks, ship’s hulls, bridges, etc. Sufficient cathodic
protection current prevents galvanic corrosion between steel and an electrolytic environment but
determining the adequacy of the level of cathodic protection at the steel-to-electrolyte interface directly
is difficult. As such, NACE International (NACE) and several other industry associations have
developed standard practices that detail consensus criteria to determine indirectly, whether or not
cathodic protection of a structure has been achieved. While the usage of these criteria has greatly
reduced the incidence of integrity failures of steel structures due to galvanic corrosion, no single
criterion has proven to be universally usable and reliable. There is currently an ongoing effort within
NACE to review and improve cathodic protection criteria performance. Two of the existing NACE
cathodic protection criteria are commonly referred to as “850 On” and “850 Polarized”. This paper will
discuss the basis for these cathodic protection (CP) criteria, their individual strengths and weaknesses,
the need for both, and how the utilization of both can be improved by NACE and by CP practitioners.
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