To determine the rate of corrosion of the steel pipe, we need to find the mass loss rate due to the corrosion current density. The corrosion current density i_corr is given as 0.008 mA/cm. We need to convert this to A/cm:i_corr = 0.008 mA/cm 1 A / 1000 mA = 8 10^-6 A/cmThe corrosion of steel involves the oxidation of iron Fe to form ferrous ions Fe . The reaction is:Fe Fe + 2eThe Faraday's constant F is 96485 C/mol, which represents the charge of 1 mole of electrons. The molar mass of iron M_Fe is 55.85 g/mol. We can now calculate the mass loss rate R using the following formula:R = i_corr M_Fe / 2 F R = 8 10^-6 A/cm 55.85 g/mol / 2 96485 C/mol = 2.29 10^-6 g/cmsNow, let's calculate the time taken for the pipe to corrode completely. We have the initial mass m_initial of the pipe as 5 kg 5000 g . We need to find the surface area A of the pipe that is exposed to corrosion. We can use the mass, density , and thickness t of the pipe to find the surface area:Volume V = m_initial / = 5000 g / 7.8 g/cm = 641.03 cmAssuming the pipe is a cylinder, the volume can also be expressed as:V = A tSo, the surface area A is:A = V / t = 641.03 cm / 0.25 cm = 2564.12 cmNow, we can find the total mass loss rate R_total by multiplying the mass loss rate per unit area R by the surface area A :R_total = R A = 2.29 10^-6 g/cms 2564.12 cm = 5.87 10^-3 g/sFinally, we can calculate the time t_corrode taken for the pipe to corrode completely:t_corrode = m_initial / R_total = 5000 g / 5.87 10^-3 g/s = 851685.5 sConverting this to days:t_corrode = 851685.5 s 1 day / 86400 s 9.85 daysSo, the rate of corrosion of the steel pipe is 2.29 10^-6 g/cms, and it will take approximately 9.85 days for the pipe to corrode completely.