Novel Multiphysics Modeling of Electroplating Process for Metallic Aerospace Components

Low hydrogen embrittlement alkaline ZnNi is increasingly used as a replacement for toxic chromated Cd. When plated onto complex high-strength steel (HSS) landing gear components, ZnNi is variable in Zn/Ni ratio and thickness, creating variable electrochemistry, and variable electrochemical potential in corroding environments. H2 is released at the metal surface during plating, most (but not all) of which is removed during the hydrogen bake. During sacrificial corrosion of the ZnNi more H2 is released, which diffuses to high stress locations, reducing fatigue life and causing stress corrosion cracking (SCC) risk. In prior work Corrdesa has developed unique modeling methodologies to determine ZnNi chemistry and thickness based on electrolyte chemistry and plating tank tooling (auxiliary anodes, shields, etc.), and has developed extensive computational corrosion modeling methodologies that combine electrodynamics and computational fluid dynamics to model hydrogen evolution across the entire surface of complex components, which is significantly more accurate than the surface potential models currently used to design tooling for electroplating. University of Virginia (UVa) has extensive experience in crack initiation and propagation and how crack initiation and propagation rate is driven by surface structure (morphology and stress) and electrochemistry (hydrogen evolution) during electroplating and corrosion. This proposal combines Corrdesa’s electrochemical measurement and modeling with UVa’s proven crack propagation measurement and modeling to demonstrate and quantitatively evaluate how the plating process and subsequent coating and substrate corrosion interact to reduce fatigue life and increase SCC risk. The ultimate aim of the project is to develop a modeling and data toolset that will allow DoD engineers to quantitatively determine, design and model the tooling requirements for ZnNi plating on HSS. Using a multi-objective optimization method that we have successfully applied to optimizing NAVAIR Al-rich primers, the toolset will be able to minimize corrosion, fatigue, and SCC risk within the constraints of production plating equipment and parameters. This toolset will be developed in Siemens Teamcenter PLM software, where it will be a commercially available toolset for use by DoD and supply-chain engineers. If needed it will be assembled as a stand-alone software package for use by NAVAIR and other DoD organizations.