When welding dissimilar metals, why might special filler or barriers be required?

When welding dissimilar metals, why might special filler or barriers be required?

• A. To mitigate galvanic corrosion and accommodate different thermal expansion
• B. To improve aesthetic appearance
• C. To increase weld cost
• D. To reduce electrode consumption

Answer: (B)

When two metals with different electrochemical potentials are joined, a galvanic couple can form at the weld that drives corrosion at the interface. They also expand and contract at different rates when heated and cooled, which can create high residual stresses and cracking in the weld and heat-affected zone. Using a special filler metal that is compatible with both base metals, or introducing a barrier/interlayer, helps isolate the metals, reduce diffusion that could form brittle intermetallics, and balance the joint’s properties. This keeps the weld both more resistant to corrosion and mechanically reliable. Aesthetic appearance is not the primary reason for this practice, and increasing cost or reducing electrode use isn’t the goal.

When two metals with different electrochemical potentials are joined, a galvanic couple can form at the weld that drives corrosion at the interface. They also expand and contract at different rates when heated and cooled, which can create high residual stresses and cracking in the weld and heat-affected zone. Using a special filler metal that is compatible with both base metals, or introducing a barrier/interlayer, helps isolate the metals, reduce diffusion that could form brittle intermetallics, and balance the joint’s properties. This keeps the weld both more resistant to corrosion and mechanically reliable. Aesthetic appearance is not the primary reason for this practice, and increasing cost or reducing electrode use isn’t the goal.