sample to the sample treated at 0.45 A cm-2
. From Eq. 2,
the lower value of Q, obtained for the samples treated at
high current density, can be correlated with an increase in
the thickness, in agreement with the results from SEM
observation.
The Nyquist impedance plots and the results of the
data fitting, for AZ91 alloy, are reported in Fig. 13b and
in Table 5, respectively. Similarly to the results obtained
for pure commercially magnesium, a decrease in the
values of Q and an increase in the values of R2 were
found for the samples with PEO treatment, in comparison
with the untreated sample, suggesting the presence of a
thicker and more protective layer. It should be noted, that
the value of R2 for the sample treated at 0.45 A cm-2 was
two order of magnitude higher than the one of the
untreated sample, whereas for commercially pure magnesium,
at the same operative conditions, this value was
only one order of magnitude higher than the one of the
untreated sample. The Nyquist impedance plots and the
results of fitting of the data for AM50 alloy are reported
in Fig. 13c and Table 5, where a behaviour very similar
to AZ91 alloy can be observed. These results evidenced
that the PEO process caused an enhancement in the corrosion
resistance of both pure magnesium and magnesium
alloys, but the improvement was more evident for magnesium
alloys, in agreement with the results coming from
anodic polarization tests.
sample to the sample treated at 0.45 A cm-2. From Eq. 2,the lower value of Q, obtained for the samples treated athigh current density, can be correlated with an increase inthe thickness, in agreement with the results from SEMobservation.The Nyquist impedance plots and the results of thedata fitting, for AZ91 alloy, are reported in Fig. 13b andin Table 5, respectively. Similarly to the results obtainedfor pure commercially magnesium, a decrease in thevalues of Q and an increase in the values of R2 werefound for the samples with PEO treatment, in comparisonwith the untreated sample, suggesting the presence of athicker and more protective layer. It should be noted, thatthe value of R2 for the sample treated at 0.45 A cm-2 wastwo order of magnitude higher than the one of theuntreated sample, whereas for commercially pure magnesium,at the same operative conditions, this value wasonly one order of magnitude higher than the one of theuntreated sample. The Nyquist impedance plots and theresults of fitting of the data for AM50 alloy are reportedin Fig. 13c and Table 5, where a behaviour very similarto AZ91 alloy can be observed. These results evidencedthat the PEO process caused an enhancement in the corrosionresistance of both pure magnesium and magnesiumalloys, but the improvement was more evident for magnesiumalloys, in agreement with the results coming fromanodic polarization tests.
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