## 3 Results and Discussion
### Inhibition Mechanism  
Various experiments conducted have shown better efficiency of the proposed mixture in inhibiting corrosion than individual inhibitors. This is due to the manifestation of a positive synergistic effect of inhibition due to the chemical compounds of banana peel and rice straw. Moreover, the higher efficiency of the mixture can be related to the formation of a more uniform protective film on the metal surface than in the case of individual extraction. The SEM analysis in Figure 10 showed that the film formed in the presence of the mixture was more uniform than in the presence of banana peel extract or rice straw extract. This behavior is associated with chemical adsorption of extracts on the metal surface through the formation of coordination bonds due to the presence of heteroatoms and pi-electrons in the structure of inhibitors and physical adsorption in the form of a mixture. This mechanism has been mentioned in previous studies of banana peel and rice straw by researchers [25; 29; 31]. In this study, FTIR and phytochemical analysis of the extracts were also completed to confirm this finding. FTIR results were obtained after immersing the metal samples in HCl solution in the presence and absence of banana peel and rice straw extracts. The results for the blank showed the absence of peaks (a constant transmittance value at all wavenumbers). Figure 12 shows the FTIR analysis in the presence of extracts at 750 ppm. The figure demonstrates that in the presence of banana peel and rice straw extracts, the spectrum was characterized by the presence of several peaks, confirming the existence of corrosion-inhibiting molecules. The results show that both extracts used were adsorbed on the surface of the steel samples, forming a protective layer. In addition, phytochemical analysis of banana peel and rice straw extracts was carried out to determine their compounds. The results showed the existence of many chemical compounds, among which gallocatechin and glycosides were the main components of banana peel extract and rice straw extract, respectively. The chemical structure of these materials is shown in Figure 13. These findings are consistent with the results of previous studies [25; 29; 43; 44].  
The high strength of chemical adsorption of the mixture compared to the extract alone is explained by the co-adsorption of heteroatoms in both green inhibitors, which simultaneously participate in surface bonds. Moreover, as shown in Figure 13, heteroatoms (pairs of free electrons in oxygen) and pi-electrons (in the aromatic rings) in the structure of gallocatechin and glycosides (as the main components of banana peel and rice straw for corrosion inhibition) can cause easier electron donation to the d-orbital of steel atoms (Fe), which leads to strong adsorption of extract molecules on the sample surface, thereby improving the corrosion protection efficiency [25; 29; 34; 45]. It should be noted that lone pairs of electrons are present in all oxygen atoms in the structure of the molecules in Figure 13.  
In addition, the formation of a compact and stable layer is associated with electrostatic interactions (physical adsorption) between protonated particles (charged inhibitor molecules INH-H\({}^{+}\)) and negatively charged surfaces [12; 29; 46; 47]. As shown in Figure 13, the main components of the extracts under study have heteroatoms in their structure. The positive charge is due to the protonation of the inhibitor molecule by H+ ions in the HCl solution. Chemical reagents containing heteroatoms can be protonated in an aggressive acidic solution according to the following relationship [29]:  
\[\text{[gallocatechin/glycoside molecules]}+\text{xH}^{+}\rightarrow\text{ [gallocatechin/glycoside molecules }-\text{H}_{\text{x}}\  
Figure 12: FTIR analysis after addition of banana peel and rice straw extracts.