To calculate the corrosion current density, we can use the mixed potential theory and the Butler-Volmer equation. The anodic and cathodic reactions can be represented as follows:Anodic reaction: Cu Cu + 2eCathodic reaction: 2H + 2e HFirst, we need to determine the exchange current densities for both the anodic and cathodic reactions. The exchange current density i can be calculated using the Tafel equation: = b * log i / i where is the overpotential, b is the Tafel constant, and i is the current density. We can rearrange the equation to solve for i:i = i / 10^ / b For the anodic reaction, we have:_anodic = E_corr - E_anodic = -0.35 V - 0 V = -0.35 Vb_anodic = 120 mV/dec = 0.12 V/decFor the cathodic reaction, we have:_cathodic = E_corr - E_cathodic = -0.35 V - -0.35 V = 0 Vb_cathodic = 60 mV/dec = 0.06 V/decNow, we can use the Butler-Volmer equation to calculate the current densities for both reactions:i_anodic = i_anodic * 10^_anodic / b_anodic - 1 i_cathodic = i_cathodic * 10^_cathodic / b_cathodic - 1 Since the corrosion potential is the point where the anodic and cathodic current densities are equal i_anodic = i_cathodic , we can set the two equations equal to each other:i_anodic * 10^-0.35 / 0.12 - 1 = i_cathodic * 10^0 / 0.06 - 1 Solving for the ratio of exchange current densities:i_anodic / i_cathodic = 10^0 / 0.06 - 1 / 10^-0.35 / 0.12 - 1 Now, we can use the fact that the exchange current density ratio is equal to the concentration ratio raised to the power of the number of electrons transferred in the reaction: i_anodic / i_cathodic = c_Cu / c_H Since the concentration of Cu is negligible compared to the concentration of H, we can assume that c_Cu 0 and c_H = 3 M: i_anodic / i_cathodic = 0 / 3 = 0This means that the anodic exchange current density is negligible compared to the cathodic exchange current density. Therefore, the corrosion current density is approximately equal to the cathodic current density:i_corr i_cathodic = i_cathodic * 10^0 / 0.06 - 1 Since the overpotential for the cathodic reaction is 0, the corrosion current density is equal to the cathodic exchange current density:i_corr i_cathodicUnfortunately, without more information about the system, we cannot determine the exact value of the exchange current density and, therefore, the corrosion current density. However, we have shown that the corrosion current density is approximately equal to the cathodic exchange current density in this system.