2.2.3. Characterization Methods

For the characterization, the methods FT-IR and XRD were performed at King Saud University's College of Science, the Department of Chemistry. In the absorbance range from 400 to 4000 cm<sup>−</sup>1, Perkin Elmer FT-IR (Waltham, MA, USA) was used to characterize the raw clay, Na clay, organoclay, and all prepared polystyrene nanocomposites. Wideangle X-ray diffraction (XRD) patterns were used to examine all the PCN samples and modified clays using an XRD (Bruker model D8 ADVANCE from Hamburg, Germany). The operating conditions were as follows: a Cu anode radiation source with a wavelength of λ = 0.154 nm, and a current and voltage generator of 40 mA and 40 kV, respectively. The experiments were conducted at a scanning rate of 0.30/sec in the 2θ = 3–50◦ range. Transmission electron microscope (TEM) (JOEL-1400 from Japan) measurements were taken

in the central laboratory for the Center of Science and Medical Studies for Female Students at KSU. All prepared films were immersed in epoxy resin and cured at room temperature overnight. They were then divided into segments with a thickness of roughly 70–100 nm using a microtome. The nanocomposite samples were placed on carbon-coated 200-mesh Cu grade, and the ultrathin segments were cut with a diamond knife to create clear images. TEM was used to examine the morphology of the pure PS, OC, and polystyrene/organoclay nanocomposite (1–5% wt.) films.

## 2.2.4. Electrochemical Methods

All electrochemical measurements were performed using a three-electrode electrochemical cell, with the C-steel as the working electrode, having a surface area of 9.95 cm2, which was calculated using a Mitutoyo gauging tool (Kanagawa, Japan). The standard Calomel electrode (SCE) served as the reference electrode, and rigid platinum foil served as the auxiliary/counter electrode, having a surface area of 100 mm2. The working electrode was polished to a mirror image by the polishing machine (Metaserve 2000, Buehler, London, UK) using emery papers of various grades (80, 220, 600, 1000). The electrodes were then washed several times with distilled water and cleaned with an ultrasonic cleaner in acetone for 2 min. The PCN solutions were cast dropwise onto the polished C-steel rods to completely cover their surfaces. The coated C-steel samples were then dried at room temperature for 1 h before being dried at 50 ◦C overnight. Another layer was added to achieve a final thickness of 100 ± 10 μm, as measured by a coating-thickness gauge (Elcometer 465, Manchester, UK) [8]. All of the electrodes were immersed in a 3.5 wt.% NaCl aqueous solution at room temperature (30 ± 0.5 ◦C).

The electrochemical measurements were performed using a Gamry Potentiostat/Galvanostat ZRA (model 3000, Warminster, PA, USA). Three electrochemical methods were used in the following order to assess the protection efficiencies of the prepared PCN coatings. The first step was to attain equilibrium. The open-circuit potential (OCP) was activated for 90 min to stabilize the system and achieve steady-state potential (ESS). The first method was electrochemical impedance spectroscopy (EIS) using Nyquist plots, with a sweep frequency from 10<sup>5</sup> to 10−<sup>1</sup> Hz and at an AC amplitude of 10 mV. The perturbation amplitude for the second approach, electrochemical frequency modulation (EFM), was 10 mV with a base frequency of 0.1 Hz. The potential 250 mV from the ESS was scanned using the fourth method, potentiodynamic polarization (Tafel plot), at a rate of 1 mV/sec. Each experiment was conducted three times, and the reported results are the averages of three similar results.

#### **3. Results and Discussion**

#### *3.1. Characterization Methods*

The following parts will exhibit the FT-IR spectra, XRD, and TEM analyses of the different types of clay: commercial Indian clay (CCIn), local Khulays clay (RCKh), and their derivatives (NaC, OC), in addition to all recorded from 1–5 wt.% PCN.
