40 17. Calculate the emf of a cell made up of iron and lead electrodes in a solution of Fe and Pb2+ of equal activity. Which electrode tends to corrode when the cell is short-circuited? THERMODYNAMICS: CORROSION TENDENCY AND ELECTRODE POTENTIALS 18. Calculate the emf as in Problem 17 in an air-saturated alkaline solution of pH = 10. Which electrode corrodes on short-circuiting the cell? (Assume that HPbO forms as corrosion product and that its activity is 0.1; also assume that iron is passive and that its potential approximates the oxygen electrode.) HPыO+H₂O+2e → Pb+30H 0° = -0.54 V