International Journal of Corrosion / 2012 / Article / Tab 3 / Research Article
Inhibitory Action of Artemisia annua Extracts and Artemisinin on the Corrosion of Mild Steel in H2 SO4 Solution Table 3 Kinetics and activation parameters for mild steel coupons in 5.0 M H2 SO4 solutions in the absence and presence of inhibitors (using the gasometric technique).
System
Rate of hydrogen evolution (cm min−1 ) Inhibition efficiency (%)
(KJmol−1 )Δ
* (KJmol−1 ) Δ
* (Jmol−1 K−1 ) 30°C 40°C 50°C 60°C 30°C 40°C 50°C 60°C 5 M H2 SO4 (blank) 0.037 0.096 0.174 0.311 — — — — 58.96 56.32 −86.00 0.1 gL−1 EEAA + 5 M H2 SO4 0.017 0.060 0.119 0.257 54.50 37.70 31.70 17.27 74.83 72.19 −39.82 0.5 gL−1 EEAA + 5 M H2 SO4 0.015 0.041 0.078 0.144 60.49 56.96 55.22 53.72 63.30 60.66 −79.28 1.0 gL−1 EEAA + 5 M H2 SO4 0.008 0.023 0.064 0.120 77.93 75.71 63.40 61.27 76.55 73.91 −40.73 2.0 gL−1 EEAA + 5 M H2 SO4 0.006 0.015 0.038 0.082 84.74 84.40 77.93 73.66 75.52 72.88 −47.53 4.0 gL−1 EEAA + 5 M H2 SO4 0.001 0.005 0.014 0.039 96.73 94.97 91.82 87.33 97.12 94.48 11.34 0.1 gL−1 AEAA + 5 M H2 SO4 0.014 0.037 0.090 0.256 62.40 60.84 48.41 17.59 80.78 78.14 −23.05 0.5 gL−1 AEAA + 5 M H2 SO4 0.011 0.032 0.082 0.168 68.94 66.18 52.91 46.06 75.58 72.94 −41.17 1.0 gL−1 AEAA + 5 M H2 SO4 0.007 0.028 0.070 0.132 79.84 70.68 59.54 57.67 80.49 77.84 −27.76 2.0 gL−1 AEAA + 5 M H2 SO4 0.005 0.018 0.047 0.090 86.38 81.05 73.20 70.96 81.03 78.39 −29.39 4.0 gL−1 AEAA + 5 M H2 SO4 0.002 0.008 0.034 0.071 94.01 91.73 80.58 77.10 99.91 97.27 25.45 0.1 gL−1 TEAA + 5 M H2 SO4 0.027 0.079 0.149 0.286 26.43 17.17 14.18 7.91 64.93 62.29 −68.71 0.5 gL−1 TEAA + 5 M H2 SO4 0.023 0.066 0.123 0.263 36.24 31.41 29.34 15.37 66.27 63.63 −65.75 1.0 gL−1 TEAA + 5 M H2 SO4 0.019 0.052 0.102 0.204 47.68 45.86 41.10 34.26 65.37 62.73 −70.39 2.0 gL−1 TEAA + 5 M H2 SO4 0.012 0.035 0.067 0.145 67.57 63.66 61.21 53.39 68.59 65.95 −63.65 4.0 gL−1 TEAA + 5 M H2 SO4 0.005 0.016 0.039 0.079 86.10 83.66 77.75 74.69 76.65 74.01 −44.14 20 mgL−1 ATS + 5 M H2 SO4 0.035 0.092 0.167 0.306 5.18 3.98 3.57 1.67 59.90 57.26 −83.33 50 mgL−1 ATS + 5 M H2 SO4 0.032 0.087 0.159 0.286 12.26 9.01 8.53 7.91 60.23 57.59 −82.80 100 mgL−1 ATS + 5 M H2 SO4 0.031 0.083 0.151 0.279 16.35 13.19 13.26 10.20 60.74 58.10 −81.57 200 mgL−1 ATS + 5 M H2 SO4 0.026 0.071 0.145 0.265 28.61 25.86 16.54 14.73 64.42 61.79 −70.80 400 mgL−1 ATS + 5 M H2 SO4 0.020 0.054 0.125 0.233 44.41 43.04 27.72 25.06 68.46 65.82 −59.73