There are few options for Hull void compartments corrosion protection including passive systems using marine grade epoxy coatings and active systems using dehumidification. Dehumidification is a cyclic process and requires Operators to run the system to maintain the humidity below 50% inside non-painted compartments. Often the void contartments are used for temporary ballast during pre-service (for topside/hull integration, for tendon lock off) and will require after platform installation to be rinsed with fresh water and drained completely in order to start the dehumidification process. Dehumidification will not work if there is standing water inside the voids. Cleaning the hull voids has been delayed due to more important facility commissioning and startup activities after the tendons are locked which can accelarate the corrosion rate in unpainted voids due to standing sea water.
While dehumidification can provide some initial cost savings, in the long run it will require equipment and piping maintenance and Operators involvement to monitor, run and maintain the dehumidification equipment and piping system in order to keep the humidity low in non-painted compartments to prevent corrosion. The Hull power requirements, watertight penetrations and piping will increase due to added dehumidification equipment and system.
The typical recommendation is to paint the void compartments.