The results of electrochemical hydrogen permeation tests are presented
for a high strength low alloy steel of the type API 5L X-65 in the no
n-implanted and nitrogen-ion-implanted conditions. The material was im
planted under a variety of conditions to produce three series of sampl
es, each with a characteristic implanted layer depth. The results for
the implanted materials, when compared with the maximum hydrogen perme
ability value determined for the nonimplanted material, indicate the e
xistence of a critical implanted layer thickness. When the depth of an
implanted layer is less than this critical value, the hydrogen permea
bility of the composite material (implanted layer and substrate) is ob
served to increase (relative to the non-implanted material). For layer
thicknesses equal to or greater than the critical value, the permeabi
lity is unnaffected or reduced respectively. It is concluded that nitr
ogen-ion-implanted layers on steel are well suited for impeding hydrog
en contamination and that the techniques employed in this study may be
exploited to design surface-engineered hydrogen contamination barrier
layers for steel.