## 4 Discussion  
Parallel features on the clean, ground steel surface that are connected to scratches before exposure to the corrosive solution are seen in Figure 2a. Figure 2b shows that the corrosion attacks in 1 M HCl follow general and pitting corrosion with clearly visible open pits with large diameters on the steel surface. The results of gravimetric measurements (Table 1) show that weight loss in the environment without an inhibitor is up to 2.5 times higher compared to a fennel fruit essential oil inhibitor and up to 2 times with an anathole inhibitor. With an increase in the concentration of the fennel fruit essential oil (from 1 mL/L to 2 mL/L), a decrease in the weight of the steel plates (% compared to the medium without inhibitors) was found by 36.25, 33.33, and 27.08%, while in the case of anathole--the trend was the opposite--there was an increase of 50.83, 50.83, and 54.58%. The data (Figure 3) show that at an essential oil concentration of 1.0 mL/L, the inhibition efficiency is 62.52%, at 1.5 mL/L, it rises to 66.68%, and at 2.0 mL/L, its value rises to 70.85%. As the concentration of the essential oil increases from 1.0 to 2.0 mL/L, the corrosion rate decreases from 0.0765 to 0.0595 mg/(cm\({}^{2}\).h). This may be due to the adsorption of the compounds contained in the oil onto the surface of the low-carbon steel. This adsorption limits the dissolution of the metal by blocking the regions of corrosive ions in an acidic environment and thus reducing weight loss by increasing the inhibition efficiency and concentration of the inhibitor [4]. The obtained results differ from the data in the literature for the fennel fruit essential oil under the same conditions of the experiment 1 M HCl environment, exposure duration 6 h and temperature 298 K:  
* [PERSON] et al. [5]: at concentration 1.00 g/L, corrosion rate 0.19 mg/(cm\({}^{2}\).h) and inhibition efficiency 41%; at concentration 1.50 g/L, corrosion rate 0.14 mg/(cm\({}^{2}\).h) and inhibition efficiency 56%; at concentration 2.00 g/L, corrosion rate 0.13 mg/(cm\({}^{2}\).h) and inhibition efficiency 59%; composition of the steel plate: 0.21% C; 0.38% Si; 0.09% P; 0.01% Al; 0.05% Mn; and 0.05% S, and the remaining % is Fe. However, the chemical composition of the essential oil is very different, with the main components being limonene (20.8%), \(\beta\)-pinene (17.8%), myrcene (15.0%), fenchone (12.5%), and piperitone oxyde (12.5%). * [PERSON] et al. [9]: at concentration 1.00 g/L, corrosion rate 0.283 mg/(cm\({}^{2}\).h) and inhibition efficiency 75%; at concentration 1.50 g/L, corrosion rate 0.192 mg/(cm\({}^{2}\).h) and inhibition efficiency 83%; at concentration 2.00 g/L, corrosion rate 0.124 mg/(cm\({}^{2}\).h) and inhibition efficiency 89%; steel plate composition: 0.370% C; 0.230% Si; 0.680% Mn; 0.016% S; 0.077% Cr; 0.011% Ti; 0.059% Ni; 0.009% Co; and 0.160% Cu, with the remaining % being Fe. However, there is no information in the material about the chemical composition of the essential oil studied by the authors. * [PERSON] et al. [29]: at concentration 1 g/L, inhibition efficiency 84.1%; at concentration 0.8 g/L, inhibition efficiency 82.7%; at concentration 0.6 g/L, inhibition efficiency 82.4%; at concentration 0.4 g/L, inhibition efficiency 78.4%; steel plate composition: 0.20% C; 0.38% Si; 0.09% P; 0.01% Al; 0.05% Mn; and 0.05% S, with the remaining % being Fe. The content of anathole is 94%. * [PERSON] et al. [30]: at concentration 1 g/L, corrosion rate 0.16 mg/(cm\({}^{2}\).h), and inhibition efficiency 67%. The chemical composition of the essential oil is very different: anathole (24%), \(\alpha\)-pinene (22%), and trans-ocimene (17.90%). There is no information about the composition of steel. These differences, in our opinion, may be due to the different composition of the researched essential oils and the steel plates used, which are much lower in carbon (0.021%) than those in the literature (from 0.20 to 0.37%).