Which statement about galvanic coupling and protection is correct?

Which statement about galvanic coupling and protection is correct?

• A. It always increases corrosion
• B. It can protect the more noble metal by sacrificing the less noble
• C. It never affects corrosion
• D. It only works in non-conductive environments

Answer: (B)

Galvanic coupling is about two different metals connected in a conductive environment forming a tiny electrochemical cell. The metal that is less noble (more easily oxidized) becomes the anode and corrodes faster, while the more noble metal acts as the cathode and is protected from corrosion. The statement that describes galvanic protection by sacrificing the less noble metal is the best because it captures this mechanism: you intentionally allow the less noble metal to corrode so the more noble metal stays protected. In real-world use, sacrificial anodes made of zinc, magnesium, or aluminum are attached to steel structures to provide this kind of protection. This doesn’t mean corrosion always increases overall; it shifts it—accelerating it on the sacrificial metal while reducing it on the protected metal. It also wouldn’t work in non-conductive environments, since an electrical path and electrolyte are needed for the galvanic cell to form.

Galvanic coupling is about two different metals connected in a conductive environment forming a tiny electrochemical cell. The metal that is less noble (more easily oxidized) becomes the anode and corrodes faster, while the more noble metal acts as the cathode and is protected from corrosion. The statement that describes galvanic protection by sacrificing the less noble metal is the best because it captures this mechanism: you intentionally allow the less noble metal to corrode so the more noble metal stays protected. In real-world use, sacrificial anodes made of zinc, magnesium, or aluminum are attached to steel structures to provide this kind of protection.

This doesn’t mean corrosion always increases overall; it shifts it—accelerating it on the sacrificial metal while reducing it on the protected metal. It also wouldn’t work in non-conductive environments, since an electrical path and electrolyte are needed for the galvanic cell to form.