I want come to know about the DLEPR test to check the sensitization of stainless steel.
You can follow the standard JIS G 0580 (1986).
For stainless steel you need 0.5M H2SO4 solution with 0.01M KSCN at a temperature of 30 °C.
You do the polarization curve starting with the potential slightly below the open circuit potential (corrosion potential) and increase it with 1.66mV/s up to the 750mV above the open circuit potential or up to some very high current density. Then (immediately afterwards) you do the scan back in reverse direction. Each curve (activation and re-activation) should have a maximum. Re-activation maximum should have lower peak. Degree of sensitization (DOS) is the ratio of the re-activation maximum (amperes) divided by activation maximum (amperes). These two peaks do not need to occur at the same potential.
This electrochemical test is performed with a potentiostat in a three electrodes configuration.
The electrolytic solution is often a mixture of H2SO4 with KSCN whose ratio can change with the stainless steel you test and someone ads also HCl (exemple:https://online.unileoben.ac.at/mu_online/voe_main2.getVollText?pDocumentNr=26062&pCurrPk=21619) .
The tested specimen has to be polished (some say at least a 100 grit finish).
This method involves polarizing the specimen anodically from the corrosion potential to some preselected passive potential using a chosen scan rate (forward scan). Then, using the same scan rate, a reverse potential scan is performed to the corrosion potential (reverse scan).
The current peak formed during the forward scan is called “activation peak” whereas the current peak formed during the reverse scan is called “reactivation peak”.
During the forward sweep, the whole surface is active and contribute to the peak current ; during the reverse sweep, only the sensitized grain boundaries contribute to the passive-active transition
The degree of sensitization is given by the ratio of the two peaks (some use maximum of currents density other use the charge) : higher is the peak , heavier sensitized is the tested specimen.
Hoping it could help.
Ther are many papers on this topic in the litterature.
I suppose using ISO 12732:2006 standards yields results with repeatability.
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