Effects of Lavandula and Ricinus Ϲommunis Oil as Inhibitors of Mild Steel Ϲorrosion in HCL and H2SO4 Media

Abstract

Lavandula and ricinus communis oils were used as inhibitors of mild steel corrosion in 0.5 M HCl and in 0.5 M H2SO4. The inhibition effects of these oils were studied at ambient temperature of 25°C. Gravimetric and potentiodynamic polarization measurement methods were used for the experiments. A Digi-Ivy potentiostat, interfaced with a computer for data acquisition and analysis was used for the potentiodynamic polarization experiments. The inhibition performance decreased with increasing concentration of the mixed inhibitors in the test media for H2SO4 and increased with increasing concentration for the HCl acid medium. For the test in H2SO4, the low inhibitor concentrations of 2ml, 4ml, 6ml/250 ml H2SO4 were relatively similar and the obtained weight loss were 0.152g, 0.254g, and 0.21g respectively. At 336 h of the experiment, the concentration of 12 ml/250ml H2SO4 hаԁ the highest recorded weight loss value of 0.821g. For similar concentrations as above, the corrosion rate values of 0.84 mm/yr, 1.40 mm/yr and 1.16 mm/yr were achieved. In 0.5M HCl, the 2 ml, 4 ml, 6 ml, 8 ml / 250 mL HCl concentrations had low but constant weight loss until 144 h. The 2ml/ 250 mL HCl concentrations recorded 0.307gweight loss at 312 hr. The 12 ml/250 mL HCl concentration performed best with 0.088g weight loss at 312 h and the corrosion rate was 0.48mm/yr. Inhibition efficiency for the 12ml/250 ml HCl inhibitor concentration was 88% and in H2SO4, it was 96.35% at 336 h. Also obtained was polarization resistance which was 3.90E+02 Ω; corrosion rate- 0.68 mm/yr and current density was 5.84E-05 A cm-2 for the 2 ml/ 250 mL H2SO4 concentration in H2SO4 test medium. Similarly, for the 12 ml/ 250 mL HCl concentration, polarization resistance recorded 3.07E+02 Ω; corrosion rate was 0.86 mm/yr; and current density (Icorr) was7.41E-05 A/cm2.