In the polarization curve, the anodic active dissolution of the treated Mg alloy was enhanced compared to the bare sample, why? The treated sample surface was modified by ions implantation.
Dear Dr. Xian Wei,
probably, the surface modification of the treated Mg alloy generates a different, and more complex, trend of the potentiodynamic polarization curves.
For more details, I suggest you to have a look at the figures 5.5a and 5.5b which are visible at the following link:
https://www.palmsenscorrosion.com/knowledgebase/polarization-curves/
Best regards, Pierluigi Traverso.
Dear Xian,
a possible explanation for the shape of your curves could be the following:
1. the cathodic behaviour of the implanted samples shows lower current densities compared to the magnesium sample, so that the electron consuming process is suppressed (which is good from the point of view of corrosion protection)
2. the anodic curvature of the bare Mg specimen is not as steep as that of the implanted one, which may be caused by the appearance of corrosion product layers on the surface. In contrast, the implanted samples show a rather strong current rise, possibly due to a more localized dissolution.
On the other hand, it is quite useless to speculate on the curves, as a lot of important information is not given: what type of magnesium (high purity?), what type of implantation (type of atoms?), what solution, polarization speed, stirred solution, etc., etc.
Now, to your short question: It is (most likely) due to a more localized corrosion! ;-)
With kind regards, Andreas
Dear Xian Wei,
in the Potentio-Dynamic Polarisation (PDP) curves as you show, the precise form does depend strongly on the voltage sweep rate and without Electro-Chemical Impedance Spectroscopy (ECIS) supplementary measurement, I would be very cautious to draw too many quantitative conclusions.
With best regards
Petr
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