Faradays law Thermodynamics and Pourbaix diagram

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Academic Year 2018-2019 Master of Science in Energy Engineering CORROSION AND MATERIAL PROTECTION Prof. A. Brenna Numerical Exercise #1 1) A zinc plate with total surface area of 1 m2 is exposed to an aggressive solution, then suffering a uniform mass loss of 2 g/day. Calculate the corrosion rate expressed in: mdd (mg/(dm2·day)), mmh (mg/(m2·h)), μm/y (Zn = 7.14 Mg/m3). 2) A home heating system is made of carbon steel (MWFe = 55.9 g/mol). Total volume is 1 m3. After the water filling of the circuit, internal corrosion of carbon steel takes place. Write the corrosion reaction and calculate the mass loss of steel assuming that oxygen content in water is 8 mg/L (MW O = 16 g/mol). 3) A steel plate has corroded in seawater. After 10 years, a thickness reduction of 3 mm is measured. Calculate the average corrosion current density. Mass density and atomic weight of iron are 7.8 Mg/m3 and 55.9 g/mol, respectively. 4) Calculate or give the general equation of the equilibrium potential or equilibrium pH of the following electrochemical/chemical reactions (consider (2.3RT)/F = 0.059): a. Fe2+ → Fe3+ + e- ([aFe3+] = 0.5 mol/L; [aFe2+] = 10-6 mol/L; E0 = +0.77 V SHE) b. O2 + 4H+ + 4e- → 2H2O (pH = 3; pH = 7; pH = 12) c. 3Fe2+ + 4H2O → Fe3O4 + 8H+ + 2e- ([aFe2+] = 10-6 mol/L; [aFe3O4] = [aH2O] = 1 mol/L; E0 = +0.98 V SHE; pH = 6) d. Ni2+ + H2O → NiO + 2H+ ([aH2O] = [aNiO] = 1 mol/L) e. Ti + H2O → TiO + 2H+ + 2e- ([aTi] = [aH2O] = [aTiO] = 1 mol/L; E0 = -1.306 V SHE; pH = 10) f. CuO + H2O → CuO22- + 2H+ ([aCuO] = [aH2O] = 1 mol/L) 5) For the metal/environment coupling reported in the table, indicate whether corrosion is possible. If so, calculate the driving voltage. Assume metal ions concentration equal to 10-6 mol/L. Metal E 0 (V SHE) z E eq,a (V SHE) Environment Eeq,c (V SHE)…