Which corrosion phenomenon occurs when different metals are in contact with each other in the presence of an electrolyte?

Which corrosion phenomenon occurs when different metals are in contact with each other in the presence of an electrolyte?

• A. Pitting Corrosion
• B. Intergranular Corrosion
• C. Exfoliation Corrosion
• D. Galvanic Corrosion

Answer: (D)

Galvanic corrosion occurs when two dissimilar metals are in electrical contact and an electrolyte is present. The metal that is more electrochemically active becomes the anode and tends to corrode, while the more noble metal acts as the cathode and is protected. Electric current flows from the anode to the cathode through the metal junction and the electrolyte, driving accelerated metal loss at the anode. The rate depends on factors like the relative surface areas (a small active area against a large noble area speeds up the corrosion of the active metal), temperature, ion concentration, and especially chlorides in salt-containing environments. In practice, this is why you isolate different metals with nonconductive spacers or coatings or choose compatible materials to interrupt the electrical path and minimize corrosion. Other forms listed involve localized attack within a single metal or its microstructure and do not require dissimilar metals in contact, so they are not the galvanic type.

Galvanic corrosion occurs when two dissimilar metals are in electrical contact and an electrolyte is present. The metal that is more electrochemically active becomes the anode and tends to corrode, while the more noble metal acts as the cathode and is protected. Electric current flows from the anode to the cathode through the metal junction and the electrolyte, driving accelerated metal loss at the anode. The rate depends on factors like the relative surface areas (a small active area against a large noble area speeds up the corrosion of the active metal), temperature, ion concentration, and especially chlorides in salt-containing environments. In practice, this is why you isolate different metals with nonconductive spacers or coatings or choose compatible materials to interrupt the electrical path and minimize corrosion. Other forms listed involve localized attack within a single metal or its microstructure and do not require dissimilar metals in contact, so they are not the galvanic type.