Yes you can use an exposed area of 0.5 cm^2. But after the potentio dynamic test you have to divide 0.5 from current value in order to calculate the current density. Generally 1 cm^2 is taken widely because current value is the current density.

Thank you Nilakantha Sahu sir.

Potentiodynamic polarization (PDP) testing is commonly used to assess the corrosion behaviour of various materials, including metals such as magnesium alloys.

The choice of the exposed area largely depends on the specificities of the equipment and the material under study. An exposed surface area of 1 cm^2 is commonly used for many corrosion tests. However, it's not an absolute rule, and smaller areas can also be used.

The exposed area influences the current density, which is the current per unit area. If you decrease the exposed area from 1 cm^2 to 0.5 cm^2 while keeping the current the same, the current density will effectively double. It is important to note that the results should be reported in terms of current density rather than just the current, to allow for comparability across different experiments.

So, to answer your question, yes, you can conduct a PDP test with an exposed area of 0.5 cm^2 on your magnesium alloy deposit. However, you must carefully record and consider this information when interpreting and reporting your results. Verifying that the smaller area won't lead to excessive polarization or problems associated with edge effects is also advisable. As long as these points are considered, your results should be valid and justifiable.

Remember that the ultimate purpose of these tests is to understand the corrosion behaviour of your magnesium alloy in its intended application. As such, the test conditions should be representative of the conditions that the alloy will face in service, as much as possible.

Thank you Joshua Depiver sir.

I agree with Joshua Depiver.

Thank you Jagadeesh Bhattarai sir.

The surface of the sample depends on the current capacity of the potentiostat.

Thank you Stefan Krakowiak sir.

Dear Dr. Prabhakar Kumar Singh ,

I answer to you as I have already done previously to a similar question.

Personally did electrochemical tests on different types of samples for research use, sometimes very small (uncoated, less than 1 cm2), incorporating them in cold resin followed by metallographic polishing and I still obtained significant results.

If possible, always work by comparison, so as to highlight the different behavior of the samples.

There are ASTM and ISO standards relating to electrochemical measurements on samples and cells and related methodology; some information you can find on the net.

I suggest you to have a look at the Gamry instruments notes, there are several, in particular I found the following very interesting:

-Rapid Electrochemical Assessment of Paint

Available at: https://www.gamry.com/application-notes/corrosion-coatings/rapid-electrochemical-assessment-of-paint/

My best regards, Pierluigi Traverso.

Thank you Pierluigi Traverso sir.