(a) A galvanized (zinc-coated) steel sheet is found to uniformly corrode with an average current density of 1.4 X 10-7 A/cm2. How many years will it take to uniformly corrode a thickness of 0.030 mm of the zinc coating?
(b) A new Al container develops pits right through its walls with an average current density of 1.25x10-4 A/cm2. If the average pit is 0.50mm in diameter and the aluminum wall is 0.85 mm thick, how many days will it take for a pit to corrode through the wall. Assume the pit has a cylindrical shape and that the corrosion current acts uniformly over the surface area of the pit. For Al corroding: Al? Al3+ + 3e-