Corrosion Damage Behavior of X65/Incoloy 825 Welded Bimetallic Composite Pipe in H2S Environment

Abstract

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For the long-term service of X65/Incoloy 825 bimetallic composite pipe girth welds in the H2S environment, the corrosion damage behavior was investigated. Characterizations of welded joints were conducted by OM, SEM, XRD, and EDS. The pitting corrosion’s 3D surface morphology of welded joints in NACE-B solution saturated with H2S was investigated. The results show that composition segregation occurs in the welding process, and the Laves phase appears between dendrites, which lead to the decrease in corrosion resistance. The maximum depth of the corrosion pit is 2.46 μm after 30 days, 4.54 μm after 60 days, and 10.94 μm after 180 days. The cell automata (CA) model of corrosion damage was established based on the MATLAB program, and the basic elements of the cell automata model were determined. Through the simulation of the electrochemical reaction and diffusion process, the influence of different parameters of the pitting corrosion morphology was determined. The simulation results were compared with experimental data, which are available for the prediction of the morphology and size of the corrosion pits on the sample surface after 300 days. The results will be beneficial for the long-term service of the bimetallic composite pipe.

Keywords

• bimetallic composite pipe
• welded joint
• microstructure
• corrosion damage
• cell automata model