The inhibition of hydrogen permeation by zinc-nickel electrodeposited alloy was investigated using the Devanathan-Stachurski permeation technique. 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. Hydrogen evolution rates and hydrogen permeation rates were followed as functions of time at different applied potentials. The hydrogen permeation inhibition for thin zinc-nickel electroplates (20 s at 10 mA cm(-2) and 10 s at 20 mA cm(-2)) 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(-2) 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.