## 2 Utilization of Various Nano-Modified Coatings for Corrosion Mitigation
### Metal/Metallic Oxide-Incorporated Nanoc Coatings
Moreover, compared to the oxygen level of the Ni-P covering in its deteriorated area, the oxygen level was greatly decreased in the Ni-P-SN deteriorated substratum (Figure 15a) and even substantially reduced in Ni-P-nSN (Figure 15c,e). Figure 15e shows that the Ni content in Ni-P-corroded nSN's interface (87.6 wt.%) was barely altered from the surface's initial level (Figure 15f) (88.5 wt%). It implies that, relative to the other samples, Ni-P-nSN has a much lower rate of Ni disintegration. Ni-P coverings could also be classified as high-P coverings due to their mean P-contents of 9 wt.% (Figure 15b) and 11 wt. % (Figure 15d,f), and Ni-P-nSN and Ni-P-SN composite coatings, respectively. As all the circumstances remain similar for regular Ni-P and the composite coverings, the increase in P concentration of about 2 wt.% in both Ni-P-nSN and Ni-P-SN composite coverings has only been seen as a result of particle integration. The increase in P concentration in this research is a sign that the metallic Ni stage in the composite coverings is diminishing while the Ni-P alloy stage is increasing. It is important to note that the passive nature of Ni-P-based coverings is improved with raising P concentration. The composite coatings' enhanced P concentration is advantageous for their corrosion-resistant  
Figure 14: Surface topologies of **(a)** Ni-P, **(b)** Ni-P-SN, **(c)** Ni-P-nSN composite, **(d,e)** Ni-P-SN and Ni-P-nSN composed of a coating (-5 μm). Reprinted with permission from Ref. [85]. MDPI (2022). characteristics. Furthermore, as both composites have almost similar P contents, the P addition to the corrosion protection capabilities of composite coverings should be identical. As a result, it is possible to consider that the added Si\({}_{3}\)N\({}_{4}\) particles' larger particle dimension is the only factor contributing to Ni-P-increased nSN's anti-corrosion performance. The addition of Si\({}_{3}\)N\({}_{4}\) NPs (20 nm) afforded the covering a more stable, defect-free interface morphology and served as excellent CIs for the Ni-P framework. In order to increase the corrosion prevention of steel in corrosive conditions, [PERSON] et al. [86] reported the development of novel sandwich-type composites centered on 5,15-(4-carboxy-phenyl)-10,20-diphenylporphyrin or 5,10-(4-carboxy-phenyl)-15,20-(4-phenoxy-phenyl)-porphyrin and MnTa\({}_{2}\)O\({}_{6}\). Using the drop-casting method, thinner coatings with a sandwich- or single-type configurations were produced on CS. By using electrochemical examinations including PDP and open circuit potential (OCP), the prevention of steel corrosion activity was assessed in corrosive environments of 0.1 M HCl. It was explained how changes in the anodic (\(\beta\)a) and cathodic (\(\beta\)c) Tafel curves might affect C\({}_{\text{R}}\). The steel electrode coated using sandwich-type layers of 5,15-(4-carboxy-phenyl)-10,20-diphenylporphyrin on the bottom surface and MnTa\({}_{2}\)O\({}_{6}\) on the upper achieved the highest corrosion prevention efficacy of 91.76%. The two bis-carboxyl-substituted porphyrins' dense and adhesive coatings were hypothesized to provide a physical protective function that underlies how the inhibitors prevent the oxidation of CS. These create massive, chemically acid-resistant supramolecular frameworks (see Figure 16), preventing the acid from coming into direct contact with the steel. In the instance of trans-porphyrin (Figure 16a), as opposed to the cis-derivative scenario, the dense coatings of quadrilateral construction blocks accumulated both in J-type and H-type operations are more prominent, which results in the physical barrier impact (Figure 16b). Figure 16b shows how the cis-porphyrin is helicoidally accumulated over small rings that link collectively while providing scope for big holes and tiny apertures, which could serve as sites of interaction between the acid and metal and the commencement of pitting corrosion.