OCP pitting seems to be too high (+- 15mV) to make EIS and Potentiodynamic measurements even after 12 hours. I have uploaded an image of the ocp curve ran for 17 hours. Is there a way making it more stable and stabilising faster?
Verify all conditions of your experiment. OCP has an unusual very negative value.
Provide more details.
My specimen is a Ti-doped organic coated low carbon steel. Measured with clapping on 14cm2 cylindrical cell, %3.5 NaCl, Standart calomel electrode as reference and graphite as counter electrode. Measured OCP of the bare steel substrate is -1,050+-2mV.
Cornel Radu
What grade of steel did you use? The value of OCP for many of steel substrates (mild steel, carbon and low steel, in general low alloyed steels) against SCE measured in NaCl solution opened to air is usually in the range of -500 - 650 mV. Sometimes depending on surface morphology slightly more negative but your value of OCP of bare steel is close to the OCP of zinc coating.
Lech Kwiatkowski Thank you for the information. Grade of the steel for the measurement is DC03 or DC04. Is there a relation between OCP value and OCP fluctuation?
You must try change a reference electrode. Repetitive fluctuations at the theoretically stable potential may be associated with the reference electrode itself .Potential values are also very low for titanium and steel.
regards
stefan krakowiak
I do work with 2 different SCE's and both of them have the same characteristics in terms of fluctuation range( Electrode impedance near 750 ohms after relaxation). After your recommendation i may be using Ag/AgCl reference electrode in the future.
Thank you for recommendation Stefan Krakowiak
regards
Ali Kaan Sünnetçioğlu
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