I used to find a project specification indicate "Anti-HIC" material. It is killed carbon steel, low carbon content & carbon equivalent, very low sulfur content. However, I never find any international standard about this material. If anyone can describe in detail about Anti-HIC material, please advise.

Hydrogen-induced cracking is caused by nascent hydrogen atoms (Ho), usually produced in aqueous hydrogen sulphide (H2S). Hydrogen atoms produced, for example, by the corrosion reaction of iron, usually combine to form hydrogen gas molecules. However, in the presence of sulphide or cyanide, the hydrogen recombination reaction is poisoned so that the nascent hydrogen atoms diffuse into the steel rather than recombining on the metal surface to form hydrogen gas. Hydrogen atoms that enter the pipeline can cause embrittlement and failure. Usually HIC failures occur within a few weeks of the pipeline being put in service.

Thanks for the reply. I do understand the mechanism of HIC. However, I don't know about specific standard for "carbon steel material" such as in ASTM for the H2S service.

The material that I explained last year come with high corrosion allowance (6.0 mm.). Then I'm not sure that should I use only killed steel with high corrosion allowance or more specific requirement about sulfur content (0.01% or less)?

It's difficult for maintenace to order only small quantity of scarce material. In my feeling (no research), the high corrosion allowance of killed carbon steel with PWHT should be enough.

Purchase NACE MR-0175, specifies SSC resistant materials.

Thanks Hush. I have that one.

The following standards suggest the guideline of material selection, test & handling to avoid SSC, SOHIC, and hydrogen blistering (for anti-HIC).

1. NACE Standards: TM0284, TM0177( for solution of HIC test), and RP0472
2. API RP945
3. Materials and fabrication practices for new pressure vessels used in wet H2S refinery service, NACE Publ.8X194, item No.24179, 1994 (USA)
4. A working guide for carbon steel equipment in wet H2S service (developed largely from oil refinery experience), EEMUA, Publ. No. 179, 1997 (EUROPE)
5. Most of the oil & gas production and refinery company specifications for sour service

P.S. : NACE MR0175 ; Only for SSC

Thomas Eun/ NACE Corrosion Specialist
www.natco.ab.ca
thomase@natco.ab.ca
thomaseun@hanmail.net