Mod 6 - Wet H2S Damage

Module from the Materials and Corrosion Curriculum curriculum.

WET H2S DAMAGE MECHANISMS · Learning Objectives · 1. Distinguish between SSC, HIC, SOHIC, and SWC damage 2. Apply NACE MR0175 and MR0103 material requirements 3. Specify hardness limits for sour service components 4. Implement inspection strategies for wet H2S service · Wet H2S Damage Mechanisms (API 571)

Mechanism	Cause	Appearance	Susceptible Materials	Key Variables	Prevention
SSC (Sulfide Stress Cracking)	High-hardness steel + wet H2S + tensile stress	Brittle transgranular cracking at welds/HAZ	CS with hardness >HRC 22, welds without PWHT	Hardness, H2S partial pressure (>0.05 psi), pH	PWHT, hardness <HRC 22 (HB 235), MR0175/MR0103
HIC (Hydrogen-Induced Cracking)	H atom diffusion at inclusions, H2 buildup	Internal blisters, step-wise cracking parallel to plate	CS plate with high S/elongated sulfides	Plate quality, S content, H2S level, pH	HIC-tested steels (NACE TM0284), low-S steel (<0.003%S)
SOHIC (Stress-Oriented HIC)	HIC with applied stress	Through-thickness HIC stacks, branched cracks	CS plate in wet H2S	Stress + HIC-susceptible steel	HIC-tested plate + low residual stress, PWHT
SZC (Soft Zone Cracking)	Low-strength HAZ in welded high-strength steel	Cracking at weld toe or HAZ	High-strength CS welds in sour service	Weld procedure, filler metal	Controlled welding, hardness testing of welds
AUBC (Alkaline Blister Cracking)	H2S + alkaline conditions (amine systems)	Similar to HIC but in alkaline environment	CS in rich/lean amine	Alkaline conditions + H2S	PWHT, HIC-resistant steels
Wet H2S Corrosion	Uniform/pitting corrosion in wet H2S + CO2	Pitting, scale formation (FeS)	CS exposed to sour water	H2S, CO2, Cl⁻, pH, temperature	Appropriate material, chemical treatment, MR0103
NACE Material Requirements for Sour Service
Standard	Scope	Key Requirement	Hardness Limit	Application	Notes
NACE MR0175	Oilfield sour service (upstream)	Materials resistant to SSC	HRC 22 (HB 235) for CS/LAS	Wellhead, drilling, production	Upstream standard
NACE MR0103	Refinery sour service	Materials resistant to SSC	HRC 22 (HB 235) for CS/LAS	Refinery process equipment	Refinery-specific version
NACE TM0284	HIC test for CS plate	Immerse in test solution, measure crack ratio	CLR <15%, CTR <5%	HIC-resistant plate for wet H2S	Qualification test
NACE SP0472	Refinery welding procedures	Weld hardness control	Weld + HAZ: HRC 22 / HV 248	All sour service welds	Welding qualification for MR0103
API RP 945	Monoethanolamine (MEA) service	Guideline for amine plant design	PWHT all CS equipment	MEA/DEA/MDEA service	PWHT mandatory even below thickness triggers
Source: NACE MR0175/MR0103, API 571, API RP 945, FOS Chief Files — Corrosion folder, IPE-EP-10-1 series

Source: Materials_and_Corrosion_Curriculum_v1.xlsx · Sheet: Mod 6 - Wet H2S Damage

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