Anticorrosion and Antimicrobial Evaluation of Sol-Gel Hybrid Coatings Containing Clitoria ternatea Modified Clay

Abstract

In this study, Clitoria ternatea (CT) was incorporated into the structure of sodium montmorillonite (Na+-MMT), then these new nanoparticles (CT-MMT) were added to sol-gel-based hybrid silanol coatings (SGC). The results of the CT-MMT investigation using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM) confirmed the presence of CT in the structure. The results of polarization and electrochemical impedance spectroscopy (EIS) tests showed that the presence of CT-MMT in the matrix improves corrosion resistance. The EIS results showed that the coating resistance (Rf) of the sample containing 3 wt.% CT-MMT after immersion was 687 Ω·cm2, while this value was 218 Ω·cm2 for pure coating. CT and MMT compounds improve corrosion resistance by blocking anodic and cathodic regions, respectively. Additionally, the presence of CT in the structure created antimicrobial properties. CT contains phenolic compounds that have the ability to suppress by membrane perturbation, reduction of host ligands adhesion, and neutralizing bacterial toxins. Therefore, CT-MMT showed inhibitory effects and killing of Staphylococcus aureus (gram-positive bacteria) and Salmonella paratyphi-A serotype (gram-negative bacteria), and also improved corrosion resistance.

The Use of Plant Extracts as Green Corrosion Inhibitors: A Review

“…Corrosion is always lurking in metal structures; this phenomenon has a slow but continuous behavior and causes major failures [31]. Although corrosion is mostly slow, in some environments, such as the sea and industrial towns, it is very rapid and severe [14,31].…”

“…Corrosion is always lurking in metal structures; this phenomenon has a slow but continuous behavior and causes major failures [31]. Although corrosion is mostly slow, in some environments, such as the sea and industrial towns, it is very rapid and severe [14,31]. In general, metals and metal-based alloys are affected by many factors such as moisture, chemicals, pollutants, fuels, and mineral raw materials, and thus, the conditions for corrosion are created [14].…”

“…Chloride ions are one of the most aggressive species that can cause corrosion and there is a high content of them in the marine atmosphere [14,15]. In coastal areas, chlorine ions dissolve in the moisture layer and cause the solubility of corrosion products to increase and the passive layers to be destroyed [14,31]. Also, a high salinity atmosphere can lead to the formation of thick layers of rust on the wet surface of carbon steel, causing it to easily separate from the metal substrate, as a result, the surface becomes unprotected and this means accelerating the corrosion process [14,34].…”

“…Protective coatings have the most important effect in preventing corrosion. In this regard, many coatings are used such as paint, polymer, metallic coating, and phosphating coating [15,31]. Meanwhile, the use of nanoparticles to strengthen the coating is common [51].…”

“…For several years, GCIs (in cluding plant extracts and fruit waste) have received much attention [30]. Many of them have antimicrobial properties in addition to anti-corrosion properties due to being rich in bioactive compounds [31]. It can be said that almost all parts of the plant such as leaves roots, bark, flowers, fruits, wood, and seeds are used to prepare the inhibitor, but the leaves are considered more often because they have the highest abundance of phyto chemicals, although this does not apply to all plants [32,33].…”