Effects of corrosion on surface characterization and mechanical properties of butt-welded joints

• Corrosion characterizations of all three zones for butt-welded joints were studied.
• Degradation of mechanical properties of corroded butt-welded joints was studied.
• Deterioration mechanisms of ductile fracture based on pitting were analyzed.

The purpose of this study is to investigate the changes in surface morphology and mechanical properties for carbon steel butt-welded joints by ageing in salt spray environment. The corrosion characterizations of the base metal, heat-affected zone and weld metal for the butt-welded joints were tested by employing a 3D profile measurement technology, the results showed that the pitting geometrical parameters of all three zones had a similar time-dependent evolution rule, namely mean pit depth, maximum pit depth and volume-box parameter all increased with the increasing exposure corrosion time, while pitting aspect ratio decreased. In addition, it should be noted that the pitting corrosion in the heat affected zone was more severe than that in the other two zones.Tensile tests of the corroded butt-welded joint specimens were performed, the results had shown that the strength, ductility and strain hardening of the corroded butt-welded joints decreased as the degree of pitting corrosion increased. In particular, compared with the corroded base metal specimens with the same conditions, a more significant reduction of the tensile ductility for butt-welded specimens was observed. Besides, the reasons for this above degradation phenomenon were analyzed by using the numerical simulation methods.