In galvanic corrosion, the anodic metal's corrosion rate typically does what?

• A. Stays the same
• B. Decreases
• C. Increases
• D. Fluctuates

Answer: (C)

When two dissimilar metals are in contact in an electrolyte, the one that is more anodic (less noble) becomes the anode and oxidizes, while the more cathodic metal is protected. This setup drives electrons from the anodic metal to the cathodic metal, pushing the anodic metal to dissolve faster than it would on its own. So, in a galvanic couple, the corrosion rate of the anodic metal typically increases. The exact rate depends on factors like the relative surface areas of the metals and the characteristics of the electrolyte, but the general outcome is accelerated anodic dissolution. For example, zinc in contact with steel in saltwater corrodes rapidly while the steel is protected. The other options don’t fit because the galvanic driving force tends to speed up the anodic dissolution rather than leave it unchanged or reduce it. Rates can vary with conditions, but the common tendency is an increased rate for the anodic metal.