Which factor increases the severity of galvanic corrosion?

The severity of galvanic corrosion is influenced by the ratio of cathode area to anode area. A higher cathode to anode area ratio means that the cathode, which is the area that is protected, is significantly larger compared to the anode, which is the area that corrodes. This increased ratio enhances the rate of corrosion at the anode because the larger cathode provides a greater surface area for the reduction reactions to occur, thereby leading to a more pronounced potential difference between the two materials.

In galvanic corrosion, the anode is the metal that is more noble and will corrode more quickly when connected to a less noble metal (the cathode). The behavior of the metals involved in the galvanic couple, combined with the surface areas of each, fundamentally affects how severely the less noble metal will corrode. Thus, a higher ratio amplifies the corrosion process by allowing the anode to corrode at an accelerated rate due to the protective effect of a larger cathode surface.

Other factors such as increased distance between the metals, larger anode area, and higher temperatures can influence corrosion mechanisms, but they do not directly contribute to a higher corrosion severity in the same way that the cathode to anode area ratio does.