Comparative Study of Protection Efficiency of C-Steel Using Polystyrene Clay Nanocomposite Coating Prepared from Commercial Indian Clay and Local Khulays Clay

Abstract

This work aimed to compare the coating protection efficiency of C-steel using two kinds of clay: a local Khulays clay (RCKh) from Saudi Arabia and a commercial clay (CCIn) from India. Clay-based polymer nanocomposites have a unique layered structure, rich intercalation chemistry, and availability at low cost. They are promising reinforcements for polymers. The raw clay for both clay types was washed before being treated with NaCl to produce sodium clay (NaC). The cationic surfactant cetylpyridinium chloride (CPC) was then used to convert the NaC into the organoclay (OC) form. Polystyrene/organoclay nanocomposites (PCNs) were prepared by combining different concentrations of organoclay (1%, 3%, and 5% OC) in toluene solvent and polystyrene (PS) as the matrix. To ensure the success of the PCN modification process, the organoclay and PCN films were characterized using a variety of techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The shifts in the FT-IR spectra after the CPC treatment of NaC confirmed the presence of CPC in the organoclay samples and the presence of OC in the PCNs. The exfoliated structure was obtained from the XRD spectrum for low clay loading (1–3% PCN), while the intercalated structure was the dominant form for the 5% PCN. The XRD results were confirmed by TEM images. To calculate the coating efficiency of the PCNs, various electrochemical methods were used. The electrochemical measurements included electrochemical impedance spectroscopy (EIS), the electrochemical frequency modulation (EFM) method, and Tafel plots. The PCN with a concentration of 1 wt.% OC has a fully exfoliated structure and higher coating efficiency than the PCNs with partially exfoliated structures (3 wt.% and 5 wt.%). It was found from the Tafel plots that commercial Indian clay has better corrosion protection (81.4%) than local Khulays clay (60.2%). A comparison with other studies using current density values shows that our results are superior to those of many studies.