what do you mean by a long period of time? do you mean emersion tests?

Dear Nasimul Eshan Chowdhury ,

Corrosion is always an interesting topic of research; we are always trying to find methods to accelerate the degradation in order to quickly access corrosion mitigation options (e.g., coatings, inhibitors, environment). It is difficult to answer your question without additional context, but I hope this helps!

EIS can provide insight into the corrosion behaviour, including the corrosion rate (polarization resistance) and reactions mechanisms (when adequately modelled using complementary analytical and/or microscopy techniques). If you are performing EIS at the open circuit potential (OCP), you are likely trying to assess the corrosion rate/performance of the coating after a defined immersion time.

As such, accelerating the corrosion test from 3 weeks or months (in your case) to sometime shorter, is difficult to do without introducing additional experimental uncertainties. For example, some methods to accelerate corrosion testing include using a more aggressive test environment (e.g., increased chloride concentration, increased acidity) or performing tests at a more anodic polarization potential than OCP; however, these changes may also influence the corrosion mechanism and thus provide erroneous results for the purpose of predicting long-term corrosion testing. For example, over time coatings could have water uptake through their pores (if present) that may not occur during shorter exposure periods. I recommend performing a literature review on accelerated environments that may be used in your case without substantially changing the corrosion mechanism.

There are other accelerated EIS tests, such as ISO 17463, that have been used in industry, but again it depends on the corrosion behaviour you are looking to understand, since this test could alter the mechanism of degradation and/or is not representative in your specific case. You can also try ASTM B117, salt spray testing, as a complementary test method for accelerated corrosion behaviour, but again, this depends on your final application and if it is representative.

To directly answer your question, Tafel testing (I assume you mean a potentiodynamic polarization scan, similar to ASTM G5) would not provide accelerated corrosion rate measurements in your case (assuming both are used for an estimate of the corrosion current density for use in determining the corrosion rate, for example).

For more information on EIS, I recommend the following:

M.E. Orazem and B. Tribollet, (2008) Electrochemical Impedance Spectroscopy. John Wiley & Sons.

http://www.doi.org/10.1002/9780470381588

R.G. Kelly, J.R. Scully, D.W. Shoesmith, and R.G. Buchheit (2002) Electrochemical Techniques in Corrosion Science and Engineering. Marcel Dekker.

All the best in your research!

Best regards,

Leo