A copper valve is used in the waste exit line from a pharmaceutical process reactor which is producing iodine-containing organics. The waste stream is composed of air-saturated 15% sulfuric acid with the following impurities: ferric sulfate, ferrous sulfate, potassium iodide and iodine. From the following electrochemical data, determine the corrosion rate of copper in this brew. Assume all Tafel constants to be 0.1.
Cu+2 + 2e- = Cu: E = 0.350 v, jo = 10-4 A/cm2
H+ + 1e- = H2: E = 0.020 v, jo = 2x10-7 A/cm2 [on Cu]
iL[H+ to H2] = 0.2 A/cm2, iL [H2 to H+] = 10-4 A/cm2
Fe+3 + 1e- = Fe+2: E = 0.850 v, jo = 8x10-5 A/cm2 [on Cu]
iL[Fe+3 to Fe+2] = 6x10-3 A/cm2, iL[Fe+2 to Fe+3] = 2x10-4 A/cm2
I2 + 2e- = 2I-: E = 0.430 v, jo = 10-3 A/cm2 [on Cu]
iL[I2 to I-] = 2x10-3 A/cm2, iL[I- to I2] = 2x10-2 A/cm2