Final answer:
Galvanic corrosion is most likely to occur when two dissimilar metals are in direct contact, such as iron and copper in plumbing, especially in the presence of oxygen and water. The metal with the more negative electrode potential, like iron, will act as the anode and corrode faster.
Step-by-step explanation:
Galvanic corrosion occurs when two dissimilar metals are in direct contact in the presence of an electrolyte, which allows for the transfer of electrons from one metal to the other. This type of corrosion is most likely to happen in environments where the two metals are exposed to oxygen and water, such as at a joint between copper and iron pipes in older homes. The standard electrode potentials, such as those for Sn (E° = -0.14 V) and Fe²+ (E° = −0.45 V), indicate that iron is more easily oxidized than tin. As a result, tin can accelerate the corrosion of iron by acting as the cathode. The presence of a scratch through a protective paint coating on an iron surface can also give rise to a galvanic cell, further increasing the risk of corrosion.