Investigation of Local Hydrogen Uptake in Rescaled Model Occluded Sites Using Crevice Scaling Laws
Abstract
The effects of occluded site geometry and applied potential on hydrogen production and uptake in a martensitic stainless steel (Fe-l3Cr-8Ni-2Mo-1Al) were explored. On planar electrode surfaces, the total hydrogen concentration was found to increase exponentially with hydrogen overpotential. The x(exp 2)/gap scaling law, where x is the pit/crevice depth and "gap" is the pit/crevice width, was utilized to rescale model pits from micrometer to millimeter dimensions. Such rescaling enabled local hydrogen measurements as a function of pit depth in rescaled pits. Two values of x(sub crit) were identified. Significant local hydrogen (H) uptake was observed at x > x(sub crit) under conditions where external surfaces were in a passive state and above the hydrogen electrode potential (EH/H+). The local potential drops below EH/H+ at a depth, x(sub crit1)= x(sub HER) and reaches the primary passivation potential (E(sub pass)) of the stainless steel at a depth, x(sub crit2) = X(sub Pass). Thus, at X > X(sub crit1), the stainless steel experiences H production and uptake but remains passivated. At X > X(sub crit2), the material absorbs hydrogen on an actively dissolving pit surfaces since the local potential drops below E(sub Pass). Nuclear reaction analysis revealed that concurrent metal dissolution and hydrogen uptake lead to significant amounts of local hydrogen absorption just beneath simulated pit surfaces.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2005
- Accession Number
- ADA450375
Entities
People
- John R. Scully
- Michael Switzer
Organizations
- University of Virginia