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Table 7 The Tafel polarization parameter values for the corrosion of mild steel in 1 M hydrochloric acid containing different concentrations of
the PII
Dose (ppm)
-Ecorr (mv)
icorr (mA/cm2)
Rp (ohm cm2)
Ba (mv)
Bc (mv)
Corr rat (lm/y)
Eff. (%)
0.0
10
512.1
529
0.052
0.0338
0.014
0.013
0.011
0.012
0.008
585.8
1,240
1,790
2,250
2,610
1,930
3,160
97.5
140.3
131.6
154.5
153
-119.9
-142.0
-139.1
-142.2
-152.9
-127
607.7
394.8
169.9
157.4
135
0.0
35
20
542.8
547.8
556.6
546.9
568.9
72
30
74
50
78
100
200
124.8
148
148.8
97.6
76
-142
84
and presence of the compound PII. As shown in Table 7 the
corrosion current density (icorr) of bare low carbon steel
electrode was 0.0520 mA cm-2 and has a corrosion rate of
607.7 lm/Y. It is clear that addition of PII to the corrosive
media decreases the corrosion current density and corrosion
rate. This decreasing is depending on the dosage of the PII.
It is clear that the addition of the PII to acid media
affected both the cathodic and anodic parts of the curves.
Therefore, these compounds behaved as mixed inhibitors.
The corrosion potential shifted to negative direction more
markedly. This shows that the effect of inhibitors on the
cathodic reaction is more observable than on the anodic
reaction. Increasing the concentration of the PII caused the
corrosion potential to be more inert.
properties against the corrosion of low carbon steel in 1 M
HCl and H2SO4 solutions at room temperature, and the
inhibition efficiency is increased by increasing the con-
centration of the inhibitors. However, the corrosion inhi-
bition of the prepared compounds depends mainly on their
solubility.
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Table 7 lists the polarization parameters for corrosion of
low carbon steel in the presence at different concentrations
of the investigated compounds. The corrosion inhibition
efficiency (gP%) is defined as:
ꢀ
ꢁ
i0corr
gP%
¼
1 ꢂ
ꢁ 100
ð6Þ
icorr
The i0corr and icorr are the corrosion current densities of
corrosive medium with and without inhibitor, respectively.
It is clear that corrosion current density decreases with
increasing the concentration of the inhibitors. The depo-
larization of both anodic and cathodic branches after
addition of the inhibitors indicates that not only was dis-
solution of the metal, but the evolution of hydrogen and
oxygen (we did not try to purge the dissolved oxygen out of
the cell) was also suppressed. Therefore, the imidazoline
derivatives cause a decrease in the corrosion rate of steel in
acid media by influencing both the anodic and cathodic
reactions. The maximum efficiency was 84% for a con-
centration of 200 ppm of PII.
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Conclusions
The results indicate that all the prepared compounds have
good surfactant properties and exhibit good inhibition
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corrosion inhibitors. Corrosion 41:28–287
123