As noted in Chap. 3, Sect.  3.6.5 , a plan for retrofit of sacrificial anodes is needed when the measured polarised potential is more positive than −800 mV (Ag/AgCl/Seawater) for carbon steels as an example. Retrofitting of sacrificial anodes for offshore structures are generally very costly and sometimes impractical. It is therefore normal practice to have at least the same design life as for the structure with minimal requirements for maintenance.