In galvanic corrosion, what is the primary cause when two different metals are in contact?

In galvanic corrosion, what is the primary cause when two different metals are in contact?

• A. Dissimilar metals in contact with an electrolyte and different surface areas
• B. Same metals in contact with air
• C. Using copper in contact with aluminum
• D. Uniform material with no contact

Answer: (A)

Two dissimilar metals placed in electrical contact with an electrolyte form a tiny electrochemical cell. The metal more prone to oxidation becomes the anode and dissolves, while the nobler metal acts as the cathode and is protected. The electrolyte is essential because it carries ions and closes the circuit, letting current flow between metals. The corrosion rate depends on the relative surface areas: if the cathode is large compared to the anode, the current density on the small anodic area increases, accelerating its dissolution. If they’re the same metal or there’s no electrolyte, galvanic action doesn’t occur, so there’s no galvanic corrosion.

Two dissimilar metals placed in electrical contact with an electrolyte form a tiny electrochemical cell. The metal more prone to oxidation becomes the anode and dissolves, while the nobler metal acts as the cathode and is protected. The electrolyte is essential because it carries ions and closes the circuit, letting current flow between metals. The corrosion rate depends on the relative surface areas: if the cathode is large compared to the anode, the current density on the small anodic area increases, accelerating its dissolution. If they’re the same metal or there’s no electrolyte, galvanic action doesn’t occur, so there’s no galvanic corrosion.