The present work utilizes a recently proposed methodology for performi
ng tests and analysing the data from electrochemical hydrogen permeati
on experiments so as to characterize the effect of surface coating lay
ers on hydrogen ingress into the sample. This methodology has been suc
cessfully applied to nitrogen ion-implanted API-5L-X65 type pipeline s
teel. Hydrogen permeation experiments were conducted using a double el
ectrolytic cell, thermostatically controlled at 308 K, containing a 0.
1 N NaOH solution in both compartments. The hydrogen permeability beha
viour of the low alloy high strength steel is significantly altered wh
en it is coated with a nitrogen ion implanted layer. The implanted lay
er was shown to possess an apparent hydrogen diffusivity much smaller
than that of the substrate steel, while presenting an apparent hydroge
n solubility considerably greater than that of the uncoated substrate.