Corrosion is primarily caused by a difference in __________.

Corrosion is primarily caused by a difference in voltage, which relates to the electrochemical processes that drive corrosion reactions. When two dissimilar metals are in contact with each other in the presence of an electrolyte, a galvanic cell can form due to the varying electrochemical potentials (or voltages) of the metals. The metal with a higher voltage (more noble metal) tends to remain protected, while the metal with a lower voltage (less noble metal) is more susceptible to oxidation and subsequent corrosion.

In essence, these voltage differences can lead to the flow of electrons, resulting in the degradation of the less noble metal. The driving force behind this electrochemical reaction is directly linked to the voltage levels present between the two materials, confirming the vital role that voltage difference plays in corrosion processes. Understanding this principle is fundamental in cathodic protection, where methods are employed to mitigate corrosion by managing these electrochemical reactions.