**4. Using chitosan-nanoparticle composite form for metal protection**

Chitosan composites have mainly been applied as inhibiting coatings and are used for corrosion protection purposes in different media. Some works have reported the preparation of composite coatings with chitosan to obtain protective systems to metal substrates [42, 44, 45]. To improve the anti-corrosion properties of the polymeric matrix, it is necessary to invest in improving the mechanical and adhesion properties through the incorporation of inorganic and organic fillers. It is reported that Nano-scaled fillers imply better barrier properties in the polymer

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**Figure 4.**

protection against corrosion.

*The Application of Chitosan-Based Compounds against Metallic Corrosion*

ing sustainable corrosion protection coatings for different metals.

more effective in corrosion protection of carbon steel.

the galvanic coupling of graphene oxide with the metal surface [51].

coatings compared to the micron-size additives [15]. In general, a schematic for

Biopolymer chitosan-based nanocomposite coatings have been investigated for protection against copper corrosion [46]. Coatings are composed of chitosan matrix with 2-mercaptobenzothiazole and silica nanoparticles. Overall, the combination of the organic corrosion inhibitor and inorganic nanoparticles enhanced the protection efficiency of chitosan coatings, which is an important advance toward develop-

Several researchers have reported the viability of chitosan composites films e.g. chitosan/ZnO nanoparticle composite for protection against corrosion for steel [47, 48] and bio-corrosion inhibition for S150 carbon steel [49]. All of these studies showed that the quality of the chitosan film was improved due to the addition of ZnO nanoparticles. Another study [50] evaluated and compared corrosion protection of carbon steel using two different systems of chitosan e.g. oleic acid-modified chitosan-graphene oxide composite coating and pure chitosan coating. In this case, it was observed that the corrosion protection of oleic acid-modified chitosangraphene oxide composite coating improved by 100 folds when compared with pure chitosan coating. Thus, oleic acid-modified chitosan-graphene oxide composite is

Another composite coating [51] consisting of graphene oxide-chitosan-silver on Cu-Ni Alloy with enhanced anti-corrosive and antibacterial properties show graphene oxide retards the diffusion of corrosive ions to the substrate and minimizes the electron transport between the electrolyte and metal, while chitosan prevents

The system chitosan/hydroxyapatite nanoparticle composites revealed that they could inhibit corrosion in steel, however, it was found that the combination of chitosan/hydroxyapatite nanoparticle with other species provides more effective protection against corrosion [52–54]. Different composites such as chitosan/ hydroxyapatite-Mg [55], chitosan/hydroxyapatite-Si [56], chitosan/hydroxyapatitemultiwalled carbon nanotube [57], chitosan/hydroxyapatite-CaSiO3 [58], and chitosan/hydroxyapatite-cellulose acetate [59] were synthesized and tested as corrosion protective layers. The composites chitosan/hydroxyapatite-Mg, chitosan/ hydroxyapatite-Si, chitosan/hydroxyapatite-CaSiO3 and chitosan/hydroxyapatitecellulose acetate demonstrated that the insertion of the third component exhibit a representative improvement in the corrosion protection of the chitosan/hydroxyapatite nanoparticle composite, except for composite chitosan/hydroxyapatitemultiwalled carbon nanotube. Consequently, it could be expected that the presence

of carbon nanotubes in any non-conductive polymer coating provides lower

*Schematic presentation of chitosan-nanoparticles composites formation process.*

*DOI: http://dx.doi.org/10.5772/intechopen.96046*

composite formation is shown in **Figure 4**.

### *The Application of Chitosan-Based Compounds against Metallic Corrosion DOI: http://dx.doi.org/10.5772/intechopen.96046*

*Chitin and Chitosan - Physicochemical Properties and Industrial Applications*

A wide range of organic heterocyclic molecules has been employed to face against metallic corrosion. In this context, azole-based compounds have shown an excellent capacity to act as good anti-corrosion compounds for several metallic materials in different corrosive environments, especially in acidic ones. The latter molecule set includes N-azole, thiazole and oxazole cyclic molecules with different architectures [40]. The chemical incorporation of azole moieties or their derivatives into the chitosan backbone has shown excellent results in terms of inhibition efficiency. Recently, a novel triazole modified chitosan (**Figure 2(d)**) has been reported to act as an efficient retarder of carbon steel corrosion, which a maximum inhibition efficiency of 97% is reached using just 200 ppm of developed chitosan derivative [41]. The benefic effect of this triazole-modified chitosan biomacromolecule against corrosion can be revealed from the reported scanning electron microscopy (SEM) images as depicted in **Figure 3**. It is clear from **Figure 3(a)** that the morphology of carbon steel surface is more rough and damaged in the absence of modified chitosan inhibitor. Nevertheless, in its presence (**Figure 3(b)**) the morphology of steel surface become smoother, which supports the protection capacity of the developed chitosan derivative. In this work, it was found that the synthesized compound could block cathodic

*SEM images of carbon steel surface (a) without and (b) with the addition of developed triazole-modified* 

sites at the metal surface via the physical and chemical adsorption process.

**4. Using chitosan-nanoparticle composite form for metal protection**

Chitosan composites have mainly been applied as inhibiting coatings and are used for corrosion protection purposes in different media. Some works have reported the preparation of composite coatings with chitosan to obtain protective systems to metal substrates [42, 44, 45]. To improve the anti-corrosion properties of the polymeric matrix, it is necessary to invest in improving the mechanical and adhesion properties through the incorporation of inorganic and organic fillers. It is reported that Nano-scaled fillers imply better barrier properties in the polymer

In addition to the amine group, i.e. –NH2, the functionalization of chitosan can be also carried out on both extra-functional groups including –OH group. This approach to amplify the inhibiting effect of chitosan has been attracting interest. We can list the example of poly (N-vinyl-imidazole) grafted carboxymethyl chitosan (**Figure 2(e)**), which is a polymer grafted chitosan. The newly synthesized chitosan derivative has exhibited interesting corrosion protection for steel metal in

**236**

acid solution [43].

**Figure 3.**

*chitosan at 200 ppm [42].*

coatings compared to the micron-size additives [15]. In general, a schematic for composite formation is shown in **Figure 4**.

Biopolymer chitosan-based nanocomposite coatings have been investigated for protection against copper corrosion [46]. Coatings are composed of chitosan matrix with 2-mercaptobenzothiazole and silica nanoparticles. Overall, the combination of the organic corrosion inhibitor and inorganic nanoparticles enhanced the protection efficiency of chitosan coatings, which is an important advance toward developing sustainable corrosion protection coatings for different metals.

Several researchers have reported the viability of chitosan composites films e.g. chitosan/ZnO nanoparticle composite for protection against corrosion for steel [47, 48] and bio-corrosion inhibition for S150 carbon steel [49]. All of these studies showed that the quality of the chitosan film was improved due to the addition of ZnO nanoparticles. Another study [50] evaluated and compared corrosion protection of carbon steel using two different systems of chitosan e.g. oleic acid-modified chitosan-graphene oxide composite coating and pure chitosan coating. In this case, it was observed that the corrosion protection of oleic acid-modified chitosangraphene oxide composite coating improved by 100 folds when compared with pure chitosan coating. Thus, oleic acid-modified chitosan-graphene oxide composite is more effective in corrosion protection of carbon steel.

Another composite coating [51] consisting of graphene oxide-chitosan-silver on Cu-Ni Alloy with enhanced anti-corrosive and antibacterial properties show graphene oxide retards the diffusion of corrosive ions to the substrate and minimizes the electron transport between the electrolyte and metal, while chitosan prevents the galvanic coupling of graphene oxide with the metal surface [51].

The system chitosan/hydroxyapatite nanoparticle composites revealed that they could inhibit corrosion in steel, however, it was found that the combination of chitosan/hydroxyapatite nanoparticle with other species provides more effective protection against corrosion [52–54]. Different composites such as chitosan/ hydroxyapatite-Mg [55], chitosan/hydroxyapatite-Si [56], chitosan/hydroxyapatitemultiwalled carbon nanotube [57], chitosan/hydroxyapatite-CaSiO3 [58], and chitosan/hydroxyapatite-cellulose acetate [59] were synthesized and tested as corrosion protective layers. The composites chitosan/hydroxyapatite-Mg, chitosan/ hydroxyapatite-Si, chitosan/hydroxyapatite-CaSiO3 and chitosan/hydroxyapatitecellulose acetate demonstrated that the insertion of the third component exhibit a representative improvement in the corrosion protection of the chitosan/hydroxyapatite nanoparticle composite, except for composite chitosan/hydroxyapatitemultiwalled carbon nanotube. Consequently, it could be expected that the presence of carbon nanotubes in any non-conductive polymer coating provides lower protection against corrosion.

**Figure 4.** *Schematic presentation of chitosan-nanoparticles composites formation process.*

As shown previously, the use of chitosan-nanoparticle composites led to improvements in the corrosion protection of different surfaces, i.e. copper and steel. Bahari *et al.* [46] concluded that addition of nanoparticles contributes to the reduction in swelling of chitosan coatings and crosslinked chitosan coatings are superior to the non-crosslinked ones vis-a-vis in mitigation of corrosion of copper surface. When, John *et al.* [47] concluded that mitigation of corrosion of mild steel by nanostructured chitosan/ZnO nanoparticle films was obtained based on chemical stability, oxidation control of coatings. Therefore, the process of corrosion control depends on the structure of the coating (polymeric matrix, crosslinking, adhesion, among other parameters).
