Electrochemical corrosion of metals (Fe–Cu, Fe–Zn, Fe–Sn) and sacrificial protection

ChemistryElectrochemistryAges 17–18

An iron bar is placed in contact with another metal in NaCl solution, distilled water, dilute acid or dry air: the metal with the lower electrode potential becomes the anode and corrodes, electrons flow to the cathode where O₂ (or H⁺) is reduced, and rust builds up. The mass-loss-over-time graph keeps the previous run for comparison: attaching Zn protects the Fe (the Zn dissolves instead), attaching Cu makes the Fe corrode faster, and a strong electrolyte with dissolved O₂ speeds up corrosion.