This study presents the structural reliability of steel plates on offshore platforms exposed to corrosion during their design period and beyond. The reliability-based design of steel plates exposed to corrosion was carried out with First Order Reliability Method coded in a computer based program, (FORM 5) and a Finite element method in a software (ABAQUS). The rate of corrosion of the steel plates was determined using a standard expression for extreme marine environment. From the results obtained using FORM 5, the safety indices ranged from 1.18 to 11.0, and a non-linear relationship exist between safety indices and thickness for different parameter variations. However, it was also noted that the design formulation is robust enough to exceed the design life prediction in the code by about 20% of the current prediction.