**3.4 SEM–EDX analysis**

Surface morphology of iron was studied by scanning electron microscopy after 1 h immersion in HCl with and without addition of the inhibitor. **Figure 12a** represents the micrograph obtained by polished steel before exposing to the corrosive medium, while **Figure 12b** showed strongly damaged steel surface due to the corrosion effect after immersion in HCl solution. SEM images of steel surface after 1 hour immersion in HCl with 1 g/100 mL TRE are shown in **Figure 12c**. It can be seen from **Figure 12a** that the iron sample before immersion seems smooth and shows some abrading scratches on the surface. Inspection of **Figure 12b** reveals that the iron surface after immersion in uninhibited HCl shows an aggressive attack of the corroding medium on the iron surface. In contrast, in the presence of 1 g/100 mL TRE (**Figure 12c**), the iron surface was corroded only negligibly. In addition, there was an adsorbed film on the iron surface that was not observed in **Figure 12b**. These results confirmed enhancement of surface coverage of steel surface that led to


#### **Table 6.**

*The percentages of the studied elements in the presence of TRE.*

*Electrochemical,Thermodynamic, Surface, and Spectroscopic Study in Inhibition of Iron… DOI: http://dx.doi.org/10.5772/intechopen.92648*

the decrease in contact between the iron and the aggressive medium. Thus, a good adsorptive protection layer that was formed by the inhibitor can efficiently inhibit corrosion of steel.

The following table shows the percentages of the studied elements in the presence and absence of TRE.

**Figure 13.** *EDX of (a) polished iron, (b) after 1 hour of immersion in HCl, and (c) treated iron in the presence of 1 g/ 100 mL extract.*

The value of <sup>Δ</sup>Ga is less than 20 kJ mol<sup>1</sup> which is an indication that physical

*SEM of polished iron (a) before immersion (b) after 1 hour of immersion in HCl 1 g/100 mL of TRE and*

**) ΔSa (J mol<sup>1</sup>**

283 0.16 13.8169 48.75 0.9986 20

293 0.04 17.7954 60.67 0.9910 303 0.13 15.2926 50.40 0.9999 313 0.15 15.4306 49.24 0.9961

**) R<sup>2</sup> ΔHa (kJ mol<sup>1</sup>**

**)**

Surface morphology of iron was studied by scanning electron microscopy after 1 h immersion in HCl with and without addition of the inhibitor. **Figure 12a** represents the micrograph obtained by polished steel before exposing to the corrosive medium, while **Figure 12b** showed strongly damaged steel surface due to the corrosion effect after immersion in HCl solution. SEM images of steel surface after 1 hour immersion in HCl with 1 g/100 mL TRE are shown in **Figure 12c**. It can be seen from **Figure 12a** that the iron sample before immersion seems smooth and shows some abrading scratches on the surface. Inspection of **Figure 12b** reveals that the iron surface after immersion in uninhibited HCl shows an aggressive attack of the corroding medium on the iron surface. In contrast, in the presence of 1 g/100 mL TRE (**Figure 12c**), the iron surface was corroded only negligibly. In addition, there was an adsorbed film on the iron surface that was not observed in **Figure 12b**. These results confirmed enhancement of surface coverage of steel surface that led to

**Element C O Cl** Without inhibitor 0.20 — — After adding HCl 0.20 29.86 1.76 With inhibitor 26.84 7.14 0.1

adsorption is dominant [30] (**Table 5**).

*The percentages of the studied elements in the presence of TRE.*

*(c) treated iron in the presence of 1 g/100 mL extract.*

**T (K) 1/K ΔGads (kJ mol<sup>1</sup>**

*Electrochemical Impedance Spectroscopy*

*Calculated parameters of Langmuir adsorption isotherm.*

**Table 5.**

**Figure 12.**

**Table 6.**

**64**

**3.4 SEM–EDX analysis**

Increasing the percentage of carbon on the surface of the iron treated with the inhibitor compared to the surface of the polished iron is presented in **Table 6** and **Figure 13**, due to the spread of the effective groups in the inhibitor and the adsorption of its electrons on the surface of the iron. Oxygen content is reduced at the surface of the iron treated with an inhibitor, compared to the surface of iron exposed to the corrosive medium, due to its interaction with iron to form a complex inhibitor film. Chlorine content is reduced in the presence of the extract compared to the iron surface exposed to corrosive medium due to the reaction of chlorine with iron forming chloride dissolved iron.

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