Using Modeling and Microfabrication for Insights into Mechanisms Controlling the Location of Crevice Attack

Microfabrication techniques and computational modeling were employed to examine crevice corrosion of different metal/electrolyte systems.  Standard thin-film fabrication techniques, employing spin-on-glass (SOG), were chosen to bridge the gap between experimental and model results. SOG provided the crevice structure with ideal geometry, inert surfaces, scale of real crevices (0.1 – 10 μm), and transparency to view crevice corrosion in situ. A multiphysics finite element package was employed to computationally model the crevice corrosion conditions of the selected metal/electrolyte systems.  The model allows a wide range of geometries to be probed, calculating the potential, current, and chemical distributions. Metal/electrolyte systems examined include: 316L stainless steel in chloride containing environments of varying pH/[Cl^-] and nickel substrates in sulfuric acid.  Location of crevice corrosion attack on nickel in sulfuric acid is known to be controlled by ohmic drop, whereas the mechanism(s) controlling its location in austenitic stainless steel remains under debate.  By being able to not only control the dimensions of the crevice, but also being able to observe the location of the attack and its movement with time allows greater insights into the controlling mechanisms in these systems.  Results from these studies will be presented and discussed.