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Calculate the corrosion current density for a zinc-copper galvanic couple, with a surface area of 10 cm² each, immersed in a 0.1 M copper sulfate solution and a 0.1 M zinc sulfate solution, respectively. Given that the exchange current density for the zinc and copper electrodes are 0.0035 A/cm² and 0.1184 A/cm², respecti

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To calculate the corrosion current density for a zinc-copper galvanic couple, we first need to determine the potential difference between the two electrodes. The standard electrode potentials for zinc and copper are -0.76 V and +0.34 V, respectively. Therefore, the potential difference  E  between the two electrodes is:E = E_copper - E_zinc = 0.34 V -  -0.76 V  = 1.1 VNext, we need to calculate the corrosion current density  i_corr  using the Tafel equation:i_corr =  i0_zinc * i0_copper  /  i0_zinc + i0_copper where i0_zinc and i0_copper are the exchange current densities for the zinc and copper electrodes, respectively.i_corr =  0.0035 A/cm * 0.1184 A/cm  /  0.0035 A/cm + 0.1184 A/cm  = 0.000411 A/cmNow, we need to calculate the corrosion rate for the zinc electrode in micrometers per year. The corrosion rate  CR  can be calculated using Faraday's law:CR =  i_corr * A * M * t  /  n * F *  where A is the surface area, M is the molar mass of zinc, t is the time in seconds, n is the number of electrons involved in the reaction, F is Faraday's constant, and  is the density of zinc.For zinc, M = 65.38 g/mol, n = 2, F = 96485 C/mol, and  = 7.14 g/cm. We want to calculate the corrosion rate in micrometers per year, so we need to convert the time to seconds:1 year = 365 days * 24 hours/day * 60 minutes/hour * 60 seconds/minute = 31536000 secondsNow, we can calculate the corrosion rate:CR =  0.000411 A/cm * 10 cm * 65.38 g/mol * 31536000 s  /  2 * 96485 C/mol * 7.14 g/cm  = 44.42 m/yearTherefore, the corrosion rate for the zinc electrode is approximately 44.42 micrometers per year.

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