Dear Kan,
Your first question has been discussed on our forum before–see the following forum topic: Meteorological codes for offshore conditions.
Modeling corrosive damage would imply a change in structural properties (e.g. mass and/or stiffness) over time. This damage would not occur instantaneously such that changes in mass and/or stiffness would need to be considered over the course of a given simulation, which is typically 10 minutes or so in length. Instead, the effect of mass and/or stiffness changes can be realized by setting up different input files characteristic of each damaged state to be considered.
Best regards,