Plates, Iron and steel--Cathodic protection

Computerized modeling techniques have been developed for the
analysis of polarization behavior, using the expected
chemical reactions and transport phenomena applicable to the
formation of calcareous deposits. The method uses the ADINAT
finite element heat transfer program and is modeled, as much
as possible, on theory rather than laboratory measurements.
In contrast, the presently available cathodic protection
computer models base their polarization behavior on
empirical data. The thesis presents experimental versus
theoretical data for a simple flat plate configuration under
cathodic protection in natural sea water over a range in
temperatures. The flat plate allows for a simplified
experimental apparatus and simplifies the derivation of
equations for the transport phenomena. The program can,
however, handle complex three dimensional geometries.
Effects of temperature and flow on the formation and
protection of calcareous deposits are also discussed in
light of the experimental results.

The influence of hydrodynamic parameters and cathodic
polarization on the formation of calcareous deposits on a
steel plate in flowing seawater is investigated. Current
density variations on the plate are determined for a
combination of applied potentials and seawater
velocities. Equations are developed to relate the
cathodic current density distribution to variations in
hydrodynamic and diffusional boundary layer thickness
along the plate for laminar and turbulent flow regimes. A
comparison of experimental current densities on a bare
plate to that predicted by theory is examined. Effects of
flow on the formation and properties of calcareous
deposits are discussed in light of recent developments in
marine cathodic protection.