A series of cathodic polarization experiments was performed in which sections of UNS G10230 steel pipe were galvanically coupled through an external resistor to aluminum anode rings. These cells were incorporated into a sea water flow loop such that the hydrodynamic conditions were quantitatively defined. Sea water velocity for the experiments was 0.03, 0.09, and 0.30 m/s. From the results, the steady-state potential versus current density trend at a given velocity was characterized in terms of the recently proposed slope parameter approach to cathodic protection design. Also, an expression for the velocity dependence of the maintenance current density was developed. Anomalous behavior was encounter for some specimens tested at velocities of 0.09 and 0.30 m/s in that these exhibited a period of depolarization followed, in some cases, by repolarization. This behavior is discussed in terms of transitory calcareous deposit protectiveness, possibly reflecting the relative amounts of Ca and Mg in the deposits at a particular time.

Subject
Depolarization, Cathodes, Water, Cathodic potential, Trends, Slopes, Current densities, Steel, Electric potential, Deposit corrosion, Polarization, Calcareous deposits, Anodes
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1998
Association for Materials Protection and Performance (AMPP)
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