Abstract
Ion vapor deposited (IVD) and electroplated Al coatings are potential replacements for electroplated low hydrogen embrittlement (LHE) Cd coatings on high strength steel substrates due to their sacrificial protection. As compared to LHE Cd coating, which needs a post baking process to remove hydrogen, both IVD and electroplated Al coatings do not introduce any hydrogen during plating process. But in corroding environments, it is possible that evolved hydrogen may diffuse through the coating into substrate and cause hydrogen damage. In this work the electrochemical permeation cell technique is used to study the effective diffusivity of hydrogen for IVD and electroplated Al coating using an LHE Cd coating as a base line. The effective diffusivities obtained from galvanostatic charging were modelled using the classical diffusion equation to obtain hydrogen permeation flux. The effective diffusivities of hydrogen in Al coated steel are further utilized to understand hydrogen embrittlement susceptibility by mechanical property measurements on Al coated, aerospace high strength steels and components.
