Numerical Simulation of the Pitting Corrosion Behavior of Stainless Steel Bellows Influenced by Varying Liquid Film Thicknesses

To advance the understanding of the corrosion behavior of stainless steel bellows in marine atmospheric environments and enhance the precision of service life predictions, this study employs finite element simulations to investigate the pitting corrosion rates and pit morphologies of bellows peaks and troughs under varying electrolyte film thicknesses. The model incorporates localized electrochemical reactions, oxygen concentration, and homogeneous solution reactions. For improved computational accuracy, the fitted polarization curve data were directly applied as nonlinear boundary conditions on the electrode surface via interpolation functions. Simulation results reveal that the peak regions exhibit faster corrosion rates than the trough regions. With increasing electrolyte film thickness (from 10 μm to 500 μm), corrosion rates at both peaks and troughs decrease progressively, and after 120 hours of simulation, the maximum corrosion rate at the peaks declines from 0.720 mm/a to 0.130 mm/a, and at the troughs from 0.520 mm/a to 0.120 mm/a, with the disparity in corrosion rates diminishing over time. Furthermore, as corrosion progresses, pits propagate deeper into the substrate, exhibiting both vertical penetration and lateral expansion along the passive film interface, ultimately breaching the substrate. This research offers valuable insights into designing corrosion mitigation strategies for stainless steel bellows in marine environments.