keywords CATHODIC PROTECTION Chemistry Chemistry, Physical Demonstration projects Electrochemistry Energy & Fuels FATIGUE-CRACK GROWTH FRACTURE-TOUGHNESS Fatigue crack growth rate Fracture toughness GASEOUS-HYDROGEN Hydrogen compatibility Hydrogen embrittlement LINE PIPE STEELS LOW-CARBON STEEL NATURAL-GAS Physical Sciences RESIDUAL-STRESS Science & Technology Steel microstructure Technology WELDING HAZ X80 STEEL