Cyclic polarization has been used to determine the susceptibility of metal to pitting corrosion, E breakdown and E reservation are the main parameters resulted from it, But someone says we can determine i corr and E corr without Tafel polarization, for me i think there is difference between the data obtained from them, i mean (i / E) corr resulted from Tafel was not confirm in cyclic.
Thanks and I appreciate you supports.
for Ecorr it doesn't really matter you do CV or tafel, where you read zero net current that is your Ecorr (easier way is to just measure OCP). For icorr though you need tafel slopes if you want to use stern-geary equation. Regarding scan rate, ASTM recommends a very slow scan rate but the ASTM standard only specifies stainless steel so that may not be applicable to all metals. The reason you should scan slow is to avoid capacitive charging of double layer that may give you incorrect current reading so you should go slow enough to almost reach equilibrium in each step.
The slow scan rate is true on non-stainless steel as well. If you are looking to accelerate experiments, anodic fixed polarization at set levels can allow for Ecorr and icorr data without the cyclic part, but requires more samples/experiments that need alot of attention versus a cyclic polarization that is set, run, and wait type of experiment.
Dear Alobaidi.
First, please tell us how did you measure these two parameters from cyclic polarization without using Tafel method? After then we can give you the necessary comments and advices...
Dear Jesus Israel Barraza-Fierro
Thanks a lot, actually I have been used different scan rate so I found different values, but as you mention the more accuracy value that is did with low scan rate. Thanks dear.
Dear Sina Jamali
I appreciated you addition, I like your common "capacitive charging of double layer that may give you incorrect current reading " so I found it experimentally. Thanks in advance.
Dear Joseph Fernandez
Sure more samples/experiments need to find the best results, amazing advice, so i think it's the best way to have deep understanding of the results!
Thanks again
Dear Fakiha Heakal
By using semi-log graph paper can find the all the current densities in corrosion parameters. First draw the 2-slop line in the active region and determine the point of interaction then put the semi-log graph paper which has scale from 0 to 9 to power some thing (10 ^2 for example). This method have been used to determine the current of passivity, breakdown, and reservation. Furthermore to the i corr if you didn't used Tafel technique. Thanks
Thanks for all, really I appreciated your answers which are give me big Knowledge with happiness.
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