Physical scale modelling (PSM) is a methodology in which a large structure subject to cathodic
protection is physically modelled by maintaining a linear relationship between the model size and the
conductivity of the electrolyte. In this way, the resistance path for current flow through the electrolyte
for the model is maintained similar to that for the full-scale structure. PSM has been used in some
NATO countries to evaluate and design shipboard impressed current cathodic protection (ICCP)
systems. One issue that is not well resolved in the use of PSM is the altered polarization behavior of
propeller materials in diluted seawater with reduced conductivity, as a result of the change in the
conditioning film on these materials. Another issue is that the polarization behavior under flow
conditions is not well represented in PSM. These issues affect the accurate modelling of shipboard ICCP
systems.