The effect of ultrasonic nanocrystal surface modification (UNSM) on the corrosion and stress corrosion cracking behavior of low carbon steel (ASTM A139) welded joint in the simulated district heating water (internal heating water) were investigated. After UNSM treatment, the microstructures of welded joint were transformed from the grain boundary ferrite and widmanstätten ferrite to polygonal ferrite accompanied by grain refinement. In electrochemical tests, the corrosion resistance of the welded joint was increased after UNSM treatment as a result of the grain refinement and improved stability of the oxide film. The stress corrosion cracking behavior was measured by slow strain rate tests with accelerated anodic and cathodic reactions. The results indicated that the UNSM treatment had a significant effect on the corrosion condition, whereas UNSM had no effect on hydrogen embrittlement.

Subject
Water, Piping, Dislocation, Metal surfaces, Microstructure, Roughness, Oxide films, Mechanical properties, Welded joints, Corrosion resistance, Ferrite, Stress corrosion cracking, Ductility
Keywords:
corrosion resistance, electrochemical impedance spectroscopy, polarization, steel, stress corrosion cracking, surface treatment, weld
© 2018, NACE International
2018
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