What happens during a concentration cell corrosion?

During a concentration cell corrosion, the primary factor leading to corrosion is the difference in electrolyte concentration across a metal surface. This phenomenon occurs when two areas of a metal surface are exposed to different concentrations of an electrolyte solution. The area with the higher concentration will have a comparatively lower electrical potential than the area with the lower concentration. This potential difference drives an electrochemical reaction where the more concentrated area experiences oxidation, leading to corrosion.

In this specific context, option B accurately captures the essence of concentration cell corrosion. It highlights the critical role of varying electrolyte concentrations in facilitating this type of corrosion.

The other options, while they touch on aspects related to corrosion, do not accurately describe the specific mechanisms at play in concentration cell corrosion. For instance, a chemical reaction with water alone does not account for the electrochemical differences caused by concentration gradients. Additionally, while temperature can influence corrosion rates in general, it is not the primary factor in concentration cell corrosion. Finally, while contact between metals can lead to galvanic corrosion, this is a different process than concentration cell corrosion.