Identification of the selective corrosion existing at the seam weld of electric resistance-welded pipes

• There is a selective corrosion in electrolyte at the seam weld of welded pipes.
• Open circuit potential differences exist between the weld and the base material.
• Seam weld has higher anodic dissolution current density than the base material.
• A galvanic coupling effect accelerates the dissolution kinetics of the seam weld.
• Selective seam weld corrosion would enhance environmentally assisted cracking.

The selective corrosion existing at the seam weld of high frequency electric resistance welded pipes of carbon steel with low sulfur content in electrolyte solutions is revealed by localized electrochemical measurements. The seam weld, mainly consisted of ferrite, has more negative open circuit potential and higher anodic dissolution current density than the base metal consisting ferrite and pearlite. Between the seam weld and the base metal, there is a galvanic coupling effect accelerating the dissolution kinetics of the seam weld such that V-shaped corrosion groove preferentially occurs at the seam weld.