If a large cathode is in contact with a small anode, the resultant corrosion would be...

If a large cathode is in contact with a small anode, the resultant corrosion would be...

• A. Mild
• B. Uniform across surface
• C. No attack
• D. Severe and extensive

Answer: (D)

In galvanic corrosion, when two dissimilar metals are in contact in an electrolyte, the more noble metal acts as the cathode and the less noble metal becomes the anode. The rate at which the anodic metal corrodes depends strongly on the ratio of cathode area to anode area: a large cathode relative to a small anode draws more current from the small metal, increasing the current density on the anodic surface and accelerating its dissolution. Therefore, a large cathode in contact with a small anode causes the small metal to corrode rapidly and extensively. This is why the result is severe and extensive corrosion on the small anode. To mitigate, keep dissimilar metals insulated from each other or use more closely matched metals to reduce galvanic driving force.

In galvanic corrosion, when two dissimilar metals are in contact in an electrolyte, the more noble metal acts as the cathode and the less noble metal becomes the anode. The rate at which the anodic metal corrodes depends strongly on the ratio of cathode area to anode area: a large cathode relative to a small anode draws more current from the small metal, increasing the current density on the anodic surface and accelerating its dissolution. Therefore, a large cathode in contact with a small anode causes the small metal to corrode rapidly and extensively. This is why the result is severe and extensive corrosion on the small anode. To mitigate, keep dissimilar metals insulated from each other or use more closely matched metals to reduce galvanic driving force.