Calculate the corrosion current density of an iron rod having a surface area of 15 cm², immersed in an acid solution (pH=3) with a temperature of 50°C. The concentration of iron ions (Fe²⁺) in the solution is 0.1 M, and the standard reduction potential of iron is -0.44 V. The Tafel slope obtained experimentally is 0.12 V/decade. Use the Tafel equation to calculate the corrosion current density (in A/cm²) of the iron rod.

Question

Calculate the corrosion current density of an iron rod having a surface area of 15 cm², immersed in an acid solution (pH=3) with a temperature of 50°C. The concentration of iron ions (Fe²⁺) in the solution is 0.1 M, and the standard reduction potential of iron is -0.44 V. The Tafel slop

Answer 1

To calculate the corrosion current density, we need to use the Tafel equation, which is given by:E = E +  b * log10 i / i  where E is the corrosion potential, E is the standard reduction potential, b is the Tafel slope, i is the corrosion current density, and i is the exchange current density.First, we need to calculate the corrosion potential  E  using the Nernst equation:E = E -  RT / nF  * log10 [Fe] / [H] where R is the gas constant  8.314 J/molK , T is the temperature in Kelvin  50C + 273.15 = 323.15 K , n is the number of electrons transferred  2 for the Fe/Fe redox couple , F is the Faraday constant  96485 C/mol , [Fe] is the concentration of iron ions  0.1 M , and [H] is the concentration of hydrogen ions  10^-pH  = 10^-3  = 0.001 M .E = -0.44 -   8.314 * 323.15  /  2 * 96485   * log10 0.1 /  0.001  E  -0.44 -  -0.045 E  -0.395 VNow we can use the Tafel equation to calculate the corrosion current density  i :-0.395 = -0.44 +  0.12 * log10 i / i  Rearranging the equation to solve for i:0.045 = 0.12 * log10 i / i log10 i / i  = 0.045 / 0.12log10 i / i   0.375To proceed further, we need the value of the exchange current density  i . Unfortunately, this value is not provided in the problem statement. The exchange current density is an experimentally determined value and depends on the specific conditions of the system. Without this value, we cannot calculate the corrosion current density  i  for the iron rod.