As long as the metal/polymer interface is intact high corrosion potentials result from the inhibition of the anodic metal dissolution whereas rather negative potentials are observed for a corroding metal/polymer interface. [ Stratmann et al. Corros. Sci. 32 (1991) 467–470]
Is this always the case? I saw some contradicting work. I must have missed some important point of the research here by
[Nazarov et al, D. Thierry, Scanning Kelvin probe study of metal/polymer interfaces, Electrochim. Acta. 49 (2004) 2955–2964],
which says that a metal-polymer interface potential can be negative or positive compared to the bare metal depending upon the dipole interaction between the metal and the polymer.
Can anyone Please point me where I have mistaken in understanding this?
Thank you very much
Metals are electropositive in nature and polymers may of different types. Some are hygroscopic, whereas other may be hydrophobic or water resistant. It also depends on the elecrolyte medium. If the electrolyte is acidic or alkaline, it may bring upon structural changes in the molecule of the polymer, e.g., protonation of polyaniline. In such a case, the coating might not be sturdy enough to protect the surface. So synthesis of some copolymer, composite structure, blocking of active groups or the addition of protective additives may be considered. As the question is raised, the details of the Metal or the polymer is not clear. So, the suggestion is, the nature of polymer based on its structure and its behavior in different electrolyte types has to be studied.
Your question wording using the term "noble" is not appropriate. The metal does not become more or less noble with a polymer coated on the surface.
But the Kelvin potential (which has nothing to do with the property "noble") changes a lot with any material adsorbed on a metal surface. Please check the definition of the oxidation potential leading to a position in the galvanic serie (more or less "noble"), which is the result of chemical reactions, while the Kelvin potential is a physical property (removing a surface electron and bring it into the vacuum).
The protection of the metal substrate by the coated polymer film will depend on the impervious nature of the polymer film coated on it.Physical compatibility of the metal with the metal is also an important factor.The film should be adherent and the coefficient of thermal expansion of the film should match with that of the metal substrate.
with all due respect, Sanjiv, thi is not an answer to Vinod's question. He asked about whether or not the metal becomes more noble, not hwether or not and how to protect a metal surface with a polymer film.
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