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NACE MR 0175 / ISO 15156 - H2S and its relevance for assessment of HIC

NACE MR 0175 / ISO 15156 - H2S and its relevance for assessment of HIC

NACE MR 0175 / ISO 15156 - H2S and its relevance for assessment of HIC

Dear all

with the new combined standard NACE MR0175 / ISO 15156-2002, several changes had been introduced (with respect to previous MR 0175 versions), still present in the most recent version of 2015.

HIC (Hydrogen Induced Cracking) is among the new features, and described in Clause 8 of ISO 15156-2.
Clause 8 states that HIC shall be considered as a potential issue even in case of "trace amounts of H2S". No threshold, and - from my point of view - the magical H2S partial pressure of 0.05 psi / 0,3 kPa is irrelevant for HIC assessment: either there is H2S (even in trace amounts) or there is none.

On the other hand, HIC as potential issue is mentioned in the context of SSC (Clause 7.1.2). This implies a relationship between the applicability of SSC (Clause 7.1.2: p(H2S) > 0,3 kPa) and HIC. Whereas Clause 8 implies strict independence.
And from my background a Chemists, I'd rate Clause 8 as more reasonable.

The background is gas sweetening of natural gas of 1,3 mbar p(H2S), less than 50% of the magical 0,3 kPa.

I'd like to ask you on advice:
? How do you implement ISO 15156, and HIC assessment in particular?
? What are your experiences?
? what carbon steel grades do you apply for HIC service?

Thank you very much,

RE: NACE MR 0175 / ISO 15156 - H2S and its relevance for assessment of HIC

Hello Steve

thank you very much for the quick feedback dazed

Regards, Reinhard

RE: NACE MR 0175 / ISO 15156 - H2S and its relevance for assessment of HIC

No problem. If you want some further information to digest, try here:


Here is a ballot proposal that I put to ISO and NACE in 2013, duly rejected as being in the too hard pile:

"Replace Clause 8 with the following:

8 Assessment of carbon and low alloy steels for their HIC/SWC performance

HIC/SWC can develop in any product form of carbon and low alloy steel exposed to
environments containing even trace amounts of H2S. This cracking threat can result in
loss of containment giving rise to a hazardous event.

NOTE Even trace amounts of H2S fall within the definition sour service, see ISO 15156-1, 3.19

The equipment user shall perform a risk assessment for a hazardous event caused by
HIC/SWC. This risk assessment should be performed in accordance with an approach
described in ISO 17776, API RP 14J, or local risk assessment regulations where these
are obligatory. Regardless of the approach used, the risk assessment process shall
address the probability and consequences of HIC/SWC failure.

NOTE: Although ISO 17776 and API RP 14J are aimed at offshore activities, the risk
assessment principles contained therein can be applied to any petroleum and natural gas facility
whether offshore or onshore. For example, the International Oil & Gas Producers Association
(OGP) have drawn heavily on ISO 17776 for their Risk Management microsite
at http://info.ogp.org.uk/RiskManagement/ that addresses exploration and production
installations generally

Where the applicable product standard, design code, or regulations do not require
HIC/SWC testing, the results of this risk assessment shall be used to determine the
need for additional testing.

Annex B provides guidance on test methods and acceptance criteria to evaluate
resistance to HIC/SWC."

Steve Jones
Corrosion Management Consultant


All answers are personal opinions only and are in no way connected with any employer.

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