📋 Case Study
Selecting Material for Offshore Pipeline
Simultaneous threats of sour service SCC, pitting, and microbial corrosion under cathodic protection
🏗️ Project Overview
Subsea gas export pipeline in Norwegian North Sea (120 km, 22 MPa, 120°C, high H₂S/CO₂)
🎯 Challenge
Simultaneous threats of sour service SCC, pitting, and microbial corrosion under cathodic protection
🔧 Design Approach
Hybrid material specification: UNS S32760 for flowlines, UNS N08825 cladding on carbon steel risers; qualified per ISO 21457 + NORSOK M-001
📐 Design Diagram
AI-generated project design illustration
📐 Key Calculations
PREN Requirement
PREN = %Cr + 3.3×%Mo + 16×%N
Result: ≥40 for flowline base metal
Ensures resistance to initiation in acidic chloride media
CPT Validation
ASTM G48 Method F at 40°C
Result: No weight loss <0.1 mg/cm² after 72h
Confirms crevice corrosion immunity at max operating temp
📊 Results
Zero corrosion-related shutdowns in first 8 years; 22% lower inspection frequency vs. legacy 2205 design💡 Lessons Learned
- •Cathodic protection potential must be monitored continuously to avoid hydrogen embrittlement
- •Clad interface integrity is more critical than bulk alloy performance
✅ Key Takeaways
- 1Cathodic protection potential must be monitored continuously to avoid hydrogen embrittlement
- 2Clad interface integrity is more critical than bulk alloy performance
📐 Prerequisites
Understand these before this topic
🔗 Engineering Applications
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