# _Laasonia inermis_ as an Active Corrosion Inhibitor for Mild Steel in Hydrochloric Acid
## 3 Results and Discussion
### Gravimetric Results
This is quite appreciable and critical in assessing the reliability and performance of corrosion inhibitors to protect metals during prolonged immersion times in aggressive environments. The extract of the _Lawsonia intermis_ functions by forming a protective film across the metal surface, thus preventing the electrochemical process responsible for corrosion from taking place. With reference to one of the identified compounds in _Lawsonia intermis_, hexadecanoic acid-2,3-dihydroxy ester, the following interactions play out. It might involve breaking the ester bond according to the following equation:The dissociated product, C\({}_{16}\)H\({}_{31}\)COOH, interacts with the mild steel's surface via the carboxyl and hydroxyl groups present to form covalent bonds with the iron in the mild steel according to the following equation:  
\[\text{Fe(s)}+\text{C}_{16}\text{H}_{31}\text{COOH}\rightarrow\text{Fe(C}_{16} \text{H}_{31}\text{COOH})_{\text{ads}}+\text{H}_{2}\]  
This adsorbed layer, according to the equation above, forms a protective layer on the organic molecule on the mild steel's surface and mitigates the corrosion process. The variation in the inhibition efficiency with the concentration of the _Lawsonia internis_ for mild steel coupons in 0.1 M and 1 M HCl solutions is shown in Figure 3. The results demonstrate that the inhibition efficiency increases with a rise in the concentration of the LI extract. At 1000 mg/dm\({}^{3}\), the inhibition efficiency values obtained for LI were relatively poor. However, by increasing the concentration to 2000 mg/dm\({}^{3}\) and 3000 mg/dm\({}^{3}\), the inhibition efficiency improved significantly to 93.90% and 97.30%, respectively. This study provides valuable insights into the effectiveness of _Lawsonia internis_ as a green cor  
Figure 1: Weight loss versus concentration for mild steel coupons in (**a**) 0.1 M and (**b**) 1 M HCl with or without _Lawsonia internis_ at 30 \({}^{\circ}\)C.  
Figure 2: Weight loss versus time for mild steel coupons in (**a**) 0.1 M and (**b**) 1 M HCl with or without _Lawsonia internis_ at 30 \({}^{\circ}\)C.  
rosion inhibitor for mild steel corrosion in acidic solutions. Increasing the concentration of the LI extract to 500 mg/dm\({}^{3}\) in 1 M HCl notably increased the inhibition efficiency to 95.5%. Further increasing the concentration to 3000 mg/dm\({}^{3}\) did not show a significant increase in the inhibition efficiency, indicating that 500 mg/L is the optimal concentration for achieving a high inhibition efficiency. At the highest inhibitor concentrations of 2000-3000 mg/dm\({}^{3}\), the inhibition efficiencies were notably high, ranging from 97.2% to 97.8%. These results highlight the effectiveness of the _Lawsonia inermis_ as an excellent inhibitor of mild steel corrosion under the studied conditions. These insights underscore the importance for optimising the inhibitor concentration for highly effective corrosion inhibition, with _Lawsonia inermis_ proving to be particularly useful in mitigating corrosion in industrial applications and practical scenarios. The work of [PERSON], [PERSON], [PERSON], and [PERSON] [16] showed a similar trend of behaviour, as the inhibition efficiency of the _Solanum melongena_ leaf extract increased with the rise in the concentration of the extract. [PERSON] et al. [17] also observed a similar behaviour, as _Caesalpinia coriaria_ pod extract acted as an effective inhibitor of the corrosion of mild steel in acidic media. When the concentration of the extract was increased to 500 mg/dm\({}^{3}\), the inhibition efficiency increased to 95.5% of that of LI. Increasing the concentration to 3000 mg/dm\({}^{3}\) did not show any significant increase in the value of the inhibition efficiency, showing that 500 mg/dm\({}^{3}\) is the optimal concentration.