Atomic hydrogen, driven off during processing, can nucleate as hydrogen gas and cause blisters to form at inclusions within the vessel’s steel shell. These "gas pockets" can become starting points for cracking which, if it continues, can cause catastrophic failure of the pressure-retaining steel wall. Concern over this phenomena, known as hydrogen induced cracking, or HIC, has led to the development of test standards by the National Association of Corrosion Engineers (NACE) to be applied to steels destined for hydrogen service.

To meet these HIC-testing standards, Fineline-processed A516 steels with a heat analysis of .002% or .001% maximum sulfur, the sulfur level being dependent on the specified test result criteria was introduced. The lower sulfur levels and smaller, shape-controlled sulfide inclusions that remain minimize the potential for hydrogen blistering and HIC.

More detailed information on HIC-testing is available on request.