I have read that, "In a typical Polarization Curve, lower corrosion current density corresponded to lower corrosion rate and better corrosion resistance." But Corrosion current density represents the rate of transfer of electrons, leading to corrosion. So, would it mean that the metal is oxidized (metal oxide formation-passive region) until a threshold potential (trans passive) and post that potential metal dissolution occurs? (For e.g., Cr to Cr2O3 to CrO3). Does it also mean that on the passive region, higher the Current density higher the metal oxide thickness?
Dear Dr. Shakthi Balan Dhinakaran ,
the current density (Icorr, often expressed in μA / cm2) is sometimes a way of evaluating the extent of uniform corrosion of a metal in a specific aqueous solution and is generally calculated by means of specific electrochemical measurements. It represents an index of the corrosion rate of the material being analysed, being able to derive from it, through the Faraday equation, the corrosion rate of the material being corroded . As well-known, a higher value of the corrosion current density indicates that a substrate has less resistance to corrosion.
The dense arrangement of atoms, for example the formation of a compact, homogeneous and defect-free state of passivation (such as the formation of oxides on certain materials such as aluminium in specific conditions), leads to the formation of a protective surface film so that the corrosion rate decreases.
We are in the presence of a system in which quality (chemical and physical type of the layer) is much more important than quantity (layer thickness).
My best regards, Pierluigi Traverso.
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