As offshore oil production moves to ever deeper waters, there is an increasing need for sulfide stress
cracking (SSC) resistant low alloy steel well casing materials with higher strength than those presently
used. Over recent years one area of study has been the development of higher strength C- type low
alloy steels for use in slight to moderately sour conditions. One emphasis has been on producing Csteel
in the 100-125 ksi strength range, beyond the strength of the C-90 and T-95 type materials that
have been traditionally used. As part of a High Pressure-High Temperature (HPHT) casing selection
program, experiments comparing hydrogen permeation and corrosion rates were performed. This
publication documents the experiments and results, and provides a tentative interpretation with respect
to the performance of the P-110 and C-110 casing steels examined. The techniques used were
electrochemical corrosion measurements using the linear polarization resistance (LPR) technique, and
the hydrogen permeation rate as measured by the hydrogen flux through the steel. Hydrogen
permeation measurements were performed on the rear side of the C-110 and P-110 steel test coupons.
Simultaneously, corrosion measurements were performed on the front face of the coupons, exposed to
the H2S containing environments.