Hi there dear Jakirahemed Md

In my opinion, there are three factors that may have influenced your results, and addressing these may help you get the desired outcome:

First, you might have an unstable surface state or oxide layer condition. This means the layer may have formed due to exposure to ambient conditions or prior electrochemical reactions before your test. To resolve this, you can either reduce the formed oxide layer by treating the specimen in a solution like 0.5 M H2SO4, then immediately transfer it to the test electrolyte for measurement, or you can polish the specimen right before placing it in the electrolyte.

Second, the scan rate during your LSV measurement could be affecting the results. I recommend using a potential window from -250 mV versus OCP to +1.1 V versus your reference electrode with a scan rate of 1 mV/s or less.

Lastly, rechecking the entire setup would be beneficial. Any intermittent discontinuity in the current path due to loose connections might cause the issues you described.

Please let me know if this helps or if you would like any further recommendations.

Thank you Soroush Asgharian for your response

I have tried even at 0.16mV/s scan rate but got the same response for different experiments on the different samples of same material

As initially for some flat scratch free polished samples ocp is becoming stable just below zero such as at -0.1 to -0.2

But didn't get proper tafel plot even after considering -0.5 to +0.5 vs ocp at 0.16mV/s scan rate with sensitivity 10^-3

Same instrument is given good results for aluminium samples

Got it,

Using -0.5 V from OCP is too low. Applying such a low voltage for a long duration (as the Scanning speed is low) may cause the formation of an unstable surface condition, as I mentioned earlier. Try using a scan rate of 1 mV/s and a narrower potential window, such as from -0.1 V to +0.5 V. This adjustment will likely resolve the problem.

okay

I will try again and update