Sir, Is corrosion occurs when rate of oxidation equals to rate of reduction? Or When the condition is at equilibrium? And What happens to metal or substance when it dissolve in unity activity solution?
At corrosion potential, the rate of oxidation is same as the rate of reduction, but for different reactions. Like, in case of Zn corrosion in deaerated pure HCl, at Ecorr, cathodic current density of hydrogen evolution is same as anodic current density of Zn dissolution. So, corrosion involves two different species (H and Zn) in this case. However, equilibrium is at Eo or Eeq, when exchange current density is experienced. At Eo or Eeq, cathodic current density for Zn(++) + 2e = Zn and anodic current density for Zn - 2e = Zn(++) are equal. So it is basically for the same half cell reduction as well as oxidation. Therefore, no net change is observed at Eeq. But, at corrosion potential, there is net change in reactions. .....For second part, unit activity cannot be maintained if corrosion process starts in an open system.
Would “metal on metal embrittlement” count as dry corrosion?
Sir, Thank you very much your valuable teaching.
Sir, Could you please categorized this forms of corrosion under dry and wet corrosion.
Very well teached sir
Full complicated
Sir, Is corrosion occurs when rate of oxidation equals to rate of reduction? Or When the condition is at equilibrium?
And What happens to metal or substance when it dissolve in unity activity solution?
At corrosion potential, the rate of oxidation is same as the rate of reduction, but for different reactions. Like, in case of Zn corrosion in deaerated pure HCl, at Ecorr, cathodic current density of hydrogen evolution is same as anodic current density of Zn dissolution. So, corrosion involves two different species (H and Zn) in this case. However, equilibrium is at Eo or Eeq, when exchange current density is experienced. At Eo or Eeq, cathodic current density for Zn(++) + 2e = Zn and anodic current density for Zn - 2e = Zn(++) are equal. So it is basically for the same half cell reduction as well as oxidation. Therefore, no net change is observed at Eeq. But, at corrosion potential, there is net change in reactions. .....For second part, unit activity cannot be maintained if corrosion process starts in an open system.