*2.2. Methods*

#### 2.2.1. Modification Methods of Clay

The scheme of synthesis of PCN starting from raw clay using present study technique is shown in Figure 1. The local Khulays clay was prepared in our laboratory from raw rocks by grinding to a fine grain size in the micrometer range [26], and the CCIn was supplied as a fine powder. An amount of 30 g of raw clay (RC) was dispersed in 500 mL of distilled water and shaken overnight to remove undesirable salts and contaminants from both clay types. After setting the solution aside for a while, the supernatant solution was removed. Three days were spent repeating this action. A 250 mL solution of 0.25 M NaCl was added to the raw clay suspension of both types of clay (RCKh and CCIn), which was then agitated overnight. This process was repeated for three days. This is referred to as the inorganic cationic-exchange modification that creates a homo ionic clay surface. Following this process, the solution suspension was separated by centrifuging at 3800 rpm for roughly 10 min. When the AgNO3 test for chloride ions was negative, the produced homo ionic clay (NaC) was washed and separated by centrifuging. After this alteration, the NaC was ground to fine powder and stored in a desiccator after being dried in an oven. The organic modification of the NaCl of both clay types was then achieved through a cationic-exchange reaction with cetylpyridinium chloride (CPC), in which organic cations replaced sodium ions to prepare the organoclay (OC).

**Figure 1.** Scheme of synthesis of PCN starting from raw clay using present study technique.

This procedure was carried out by dispersing 5 g of NaC from both clay types in 500 mL of distilled water, stirring the solution, and leaving it overnight. CPC solution was made by dissolving 3.58 g of cetylpyridinium chloride (two times the CEC of clay) in 100 mL distilled water. The CPC surfactant solution was added dropwise to the NaC suspension while vigorously stirring, and the mixture was stirred for 24 h at room temperature to ensure CPC insertion within the clay layers. The OC was collected and separated by centrifugation at 3800 rpm for about 10 min, followed by several washes with distilled water until no chloride ions were found in the solutions. The organoclay was oven-dried overnight before being ground with a mortar and pestle to a fine grain size in the micrometer range and stored in a desiccator [17].

#### 2.2.2. PCN Preparation Methods

Polystyrene/organoclay (PS/OC) composites, or PCNs, were prepared utilizing solution techniques, with the OC contents ranging from 1% to 5%. A specific amount of organoclay (0.02, 0.06, or 0.1 g) was added to 10 mL of toluene solvent in 50 mL glass bottles, and the mixture was magnetically agitated for 24 h at room temperature. The next day, two grams of PS was added to the organoclay suspension, which was magnetically stirred for six hours at room temperature. The PS/OC (PCN) mixture was then subjected to 10 min of sonication. For the characterization methods, the PCN solutions were cast into Petri dishes and allowed to dry at room temperature for 24 h before being delicately removed from the glass surface [26]. Figure 1 shows the process of preparing a PS/OC nanocomposite from raw clay to the final goal of preparing the coating protecting the C-steel using PCN.
