What does the spec that you are working with say?
Each of the specs lists alloys and the limits for H2S, temp, pH, and other criteria.

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P.E. Metallurgy, consulting work welcomed

NACE 0175, as i want to use sa-179 hic material in gas cooler with 1000ppm at 275°f.

As much as you want if the carbon steel has the correct properties. This is from a cracking point of view. High H2S may cause other corrosion issues.

https://res.cloudinary.com/engineering-com/raw/upload/v1678352593/tips/Interpretation_c12rtq.docx

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

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

I don´t know your operation pressure, but i think for a partial pressure of 0.05 psia, you are well inside in materials required by NACE 0175

https://www.bsee.gov/sites/bsee.gov/files/09-g31.p...

As Mr. Jones pointed out, the NACE spec just addresses cracking.
You need to also consider all other forms of corrosion that might impact service.

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P.E. Metallurgy, consulting work welcomed

Partial pressure 1.14 psi

Quote (ENGRANIA)

What is the partial pressure limit of wet H2S for carbon steel at what temperature

NACE MR0175 is a widely spread practice but actual limits depends on industry. What is your industry?

Natural gas air cooler

@ENGRANIA
This is an equipment type, not an industry. Check ISO 17945, ISO 21457, ISO 15156, NACE 8X194, NACE MR0103, NACE RP0296 for applicability. Note that standard applicable is affected by CO2 content and similar factors. Also para. 8 API 581 and DNVGL's report #14671 "Neutral and High pH SCC" might be useful.

Nothing like a bit of carpet bombing

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

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