What does the increase or decrease of solution resistance, charge transfer resistance and pore resistance signify in the corrosion of metals? How does these parameters affect the coating in corroding solution?
Dear Meeta Ashok Kamde
The charge transfer resistance (Rct) is a function for the electrochemical corrosion reactions intensity at coating/metal interface. The higher value of (Rct) implies the higher integrity of the coating system and then the slower development of corrosion reactions under the coatings.
Electrical resistance of solution (Rs) is highly smaller than the coatings resistance (Rf) , so the variation of (Rf) is mainly depends on the degree of solution permeation through the coating thickness .The quick decline of (Rf) suggested that solution permeation rate into coatings is high, due to the existence of initial connecting of micro-pores in the coating.
The polarization resistance Rp (Rp = Rct + Rf) is used to evaluate the corrosion resistance of the coating system materials, the greater Rp values, the higher corrosion resistance of the metal and higher coating integrity.
Finally the higher coatings integrity means that coatings are protective , pores free, crack free, coherent, adherent and chemically stable.
Best regards
Dear Meeta Ashok Kamde
The charge transfer resistance (Rct) is a function for the electrochemical corrosion reactions intensity at coating/metal interface. The higher value of (Rct) implies the higher integrity of the coating system and then the slower development of corrosion reactions under the coatings.
Electrical resistance of solution (Rs) is highly smaller than the coatings resistance (Rf) , so the variation of (Rf) is mainly depends on the degree of solution permeation through the coating thickness .The quick decline of (Rf) suggested that solution permeation rate into coatings is high, due to the existence of initial connecting of micro-pores in the coating.
The polarization resistance Rp (Rp = Rct + Rf) is used to evaluate the corrosion resistance of the coating system materials, the greater Rp values, the higher corrosion resistance of the metal and higher coating integrity.
Finally the higher coatings integrity means that coatings are protective , pores free, crack free, coherent, adherent and chemically stable.
Best regards
Dear Mr. Hussein j. H. AlAtia, Thank you for your complete and helpful answer.
Dear Mr. Hussein j. H. AlAtia sir,
Thank you very much for complete explanation
These parameters are related with each resistance of the equivalent circuit, being Rs: the solution resistance, Rp: the pore resistance and Rct: the charge transfer resistance
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