Abstract Fitness-for-service (FFS) assessment procedures evaluate whether flawed critical-pressure components are fit for purpose and aid in determining their suitability for continued operation. This dissertation investigates the effect of plasticity material models on the calculated allowable pressures in Level 3 Fitness for Service assessment of corroded piping components. Three material models are considered: Elastic Perfect-Plastic, Elastic Bi-Linear Plastic and Elastic Multi-Linear Plastic. Two cases of corroded piping components were first modelled using SolidWorks, imported into the Ansys Workbench environment, and the analyses performed using the developed material models. The results were compared to known experimental burst pressures to establish the validity of the material models and the Finite Element Analysis (FEA) applied. Following this analysis was performed on a more realistic scenario with an operating piping component on the TAQA Harding offshore platform. The multilinear material model was found to overall be the most accurate model for investigating the pipe materials behaviour under load and for finding the failure/burst pressures. However, it also requires a lengthier set up time for the material model as well as more costly computational time. The Perfect plastic model as well as the bi-linear models provided results of sufficient accuracy but crucially less computational time as well as set up for the material model. Although the multilinear model provided the most accurate values versus the experimental figures, upon applying the necessary ASME design codes, the allowable load values, most prominently for the multilinear model, are drastically reduced and therefore does not serve as an advantage over the much more simple Perfect-Plastic material model. However, the analysis shown provides still valid assessment methods for FFS according to the ASME standards.