Hydrogen permeation inhibition by zinc and zinc-nickel alloy electrodeposition

An experimental and theoretical study was carried out to determine the effects of zinc and zinc-nickel electroplates on the inhibition of hydrogen permeation into substrate iron. The coupled discharge-recombination hydrogen evolution mechanism and associated hydrogen permeation mechanisms were studied in detail. Several different permeation mechanisms were deduced to explain experimental hydrogen permeation data. A generalized steady state coupled discharge-recombination (CDR) model was suggested for use in explaining experimental data. In addition, an experimental method was developed to estimate the diffusion resistance of electroplated metals on metal substrates with known diffusion resistances. A dynamic model for hydrogen permeation was developed to provide simulations for comparison to experimental data. Kinetic parameters for the model were determined from steady state model regressions of experimental data. Simulations for iron and zinc electroplated on iron were shown.; The rate of hydrogen permeation through an iron foil with consecutively electroplated thin zinc layers was studied in detail. Hydrogen evolution rates and hydrogen permeation rates were followed as functions of time at different applied cathodic potentials. Hydrogen evolution and permeation decreased with each successive zinc layer until reaching an average of 93% and 96% inhibition, respectively, as compared with bare iron.; The inhibition of hydrogen permeation by zinc-nickel electrodeposited alloy was also investigated. The hydrogen evolution and hydrogen permeation rates for the zinc-nickel alloy electrodeposits on iron are compared with the rates for bare iron, zinc electroplated on iron, and nickel electroplated on iron. The hydrogen permeation inhibition for thin zinc-nickel electroplates (20 s at 10 mA/cm{dollar}sp2{dollar} and 10 s at 20 mA/cm{dollar}sp2{dollar}) averaged 80% and intermediate to that of nickel and zinc. This inhibition was considered to be mostly due to kinetic effects. Zinc-nickel electroplated for 20 and 40 min. at 10 mA/cm{dollar}sp2{dollar} inhibited the hydrogen permeation greater than 95% as compared to bare iron. This inhibition was due to both kinetics and the barrier effect caused by the diffusion resistance of the membrane.