What measures mitigate galvanic corrosion in dissimilar metal welding?

• A. Use different filler metals for every joint.
• B. Electrode selection, coatings, thermal compatibility, electrical isolation where needed.
• C. Ignore coatings.
• D. Keep metal in water.

Answer: (B)

Galvanic corrosion happens when two dissimilar metals are in electrical contact in the presence of an electrolyte, so a corrosion cell forms at the weld joint. The way to mitigate this in welding is to manage both the electrochemical differences and the path the current would take. Choosing an electrode (filler metal) that is chemically compatible with the base metals reduces the potential difference and the driving force for galvanic attack. Applying protective coatings or sealants over the joint keeps moisture and electrolytes away from the metal interface, breaking the electrochemical circuit. Ensuring thermal compatibility—by selecting appropriate materials and controlling heat input so the weld and base metals don’t develop problematic microstructures or excessive residual stresses—helps prevent localized attack. Electrically isolating the metals where feasible, using insulating barriers or coatings to interrupt the electrical connection, further stops galvanic currents from forming. Together, these practices lower the galvanic driving force and the availability of electrolyte at the joint, reducing corrosion. Using different fillers for every joint would introduce more mismatches, ignoring coatings leaves the joint exposed to moisture, and keeping metal in water creates the very electrolyte environment galvanic corrosion needs.