Hydrogen embrittlement suceptibility of steel armour wires for flexible pipes
Peer reviewed, Journal article
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Original versionInternational Corrosion Conference Series. 2020, .
Flexible pipes are frequently used both as flowlines and risers in the oil and gas industry. A flexible pipe has a complex structure consisting of layers of polymer and metallic materials. The armor wire layers – shielded with polymer materials from seawater on the outside and well fluid on the inside – are the load and pressure bearing parts. Due to diffusion from the well fluid and/or damage of the outer polymer layer, the annulus can be water-filled, and armor wire can corrode. In this work, the susceptibility to hydrogen embrittlement (HE) with the presence of atomic hydrogen due to cathodic polarization has been investigated for six different tensile armor wire materials. Samples were exposed to Slow Strain Rate testing (SSRT) in 3.5% NaCl solution and cathodic polarization to -1.1 and -1.4 VAg/AgCl at room temperature. Reference samples without hydrogen charging were tested in air for comparison. Stressstrain curves, reduction in area (RA) and the microstructure of the fracture surfaces were investigated. The HE susceptibility tended to increase with the carbon content, strength and hardness and the materials tended to be more brittle when charged to -1.4 VAg/AgCl than -1.1VAg/AgCl.