Galvanic corrosion occurs when dissimilar metals are in contact and an electrolyte is present. How is it usually recognized?

• A. Dissimilar metals in contact with electrolyte
• B. Corrosion buildup at the joint between the metals
• C. Uniform thinning of material away from joints
• D. Pitting near fasteners

Answer: (B)

Galvanic corrosion shows up as corrosion concentrated at the contact area between two different metals. When a less noble metal is in electrical contact with a more noble metal in the presence of an electrolyte, electrons flow from the active metal to the passive one. The active metal becomes the anode and dissolves at the interface, producing corrosion products right at the joint between the metals. That localized attack at the joint is the telltale sign you’d recognize in the field. The mere presence of dissimilar metals in an electrolyte is what enables this, but the observable cue is the buildup of corrosion right at the metal–metal interface. Uniform thinning away from joints or pitting near fasteners describe different corrosion patterns that aren’t the hallmark of galvanic corrosion.