**6. Anticorrosive properties of layered silicate nanocomposites**

It is well known that polymeric coatings are not permanently impenetrable, as the presence of defects in the coatings will lead to the formation of the pathways for the corrosive species to reach and attack the metallic surface, and a localized corrosion will be initiated. Various fillers such clays as were incorporated into the polymeric coatings to improve their barrier properties by reducing their permeability and increase the length of the diffusion pathways for oxygen and water species [52]. Indeed, the addition of clay as filler creates a maze that impedes the diffusion of corrosive molecules as illustrated in **Figure 2**. The use of clay as pigments appears to be one of the promising solutions to enhance the corrosion performance of nanocomposites. This section presents an overview on the recent advances of using of polymer-clay nanocomposites for corrosion protection.

Polymer-Clay Nanocomposites for Corrosion Protection http://dx.doi.org/10.5772/intechopen.74154 69

**Figure 2.** The difference between conventional composite and nanocomposites.

in the literature [45, 46]. In general, the corrosion protection methods commonly used are mainly organic and metallic coatings, inhibitors, cathodic, and anodic protection. This latter

The use of organic coatings on metal is usually an effective way to protect metal surfaces from corrosion while still preserving the desirable physical and mechanical properties of the metal [47, 48]. Corrosion on a bare metal surface is very complex process in itself, as the morphology of the corrosion layers formed on the surface and corrosion rate depends on several factors [49]. To evaluate the performance of any organic coatings, several parameters must be taken into consideration such as the permeability to water and oxygen, adhesion performance to the metal, coating thickness, ionic conductivity, as well as pore size distribution [50]. Commonly, the corrosion mechanism of an organic coating to protect the metal against corrosion can be divided into three groups: the electrochemical effect, the physicochemical effect, and the adhesion to the substrate [8]. The organic coating is a complex formulation of variety of materials each having a specific function. Examples of those materials include, but not limited to the following: polymeric materials, solvents, pigments, and various additives. Organic coating simply acts as a barrier between the metal surface and the surrounding environment. The barrier ability of such coating might be attributed to its structure or due to some additives or pigments implemented inside the coating. For this reason, understanding the nature and the constituents of the coating to be applied is essential to predict the performance of this coating as a corrosion protective technique. There are several reasons that can lead to failures in the coating applied, and the most common failures and the reasons leading to such failures are the permeability of the coating, adhesion, blistering, and cathodic delamination. Importantly, it was reported that a poor coating applied to a well-prepared surface is better than a good coating applied to a poorly prepared surface [51]. Contaminations on the surface of the metal can cause a direct failure to the applied coating. These contaminations can be the reason for a poor coating adhesion, which is one of the most critical factors controlling the quality of the coating. It is also well known and documented that no matter how good the coating is, the corrosion still can take place under the coating if the surface is

is relatively new, and it was first demonstrated and tested by Edeleanu 1954 [47].

68 Current Topics in the Utilization of Clay in Industrial and Medical Applications

**6. Anticorrosive properties of layered silicate nanocomposites**

mer-clay nanocomposites for corrosion protection.

It is well known that polymeric coatings are not permanently impenetrable, as the presence of defects in the coatings will lead to the formation of the pathways for the corrosive species to reach and attack the metallic surface, and a localized corrosion will be initiated. Various fillers such clays as were incorporated into the polymeric coatings to improve their barrier properties by reducing their permeability and increase the length of the diffusion pathways for oxygen and water species [52]. Indeed, the addition of clay as filler creates a maze that impedes the diffusion of corrosive molecules as illustrated in **Figure 2**. The use of clay as pigments appears to be one of the promising solutions to enhance the corrosion performance of nanocomposites. This section presents an overview on the recent advances of using of poly-

contaminated.

Different kinds of polymers were used to prepare nanocomposites coatings such as conjugated polymers and thermoplastic polymers [53]. Using the in-situ thermal polymerization, Yeh and colleagues prepared a series of polymer-clay nanocomposite by dispersing layered montmorillonite (MMT) clay into an organic poly(methyl methacrylate) matrix [54]. Firstly, methyl methacrylate monomers were intercalated into the montmorillonite that was exfoliated by cation-exchange reaction with quaternary alkylammonium cations or alkylphosphonium cations followed by a typical free-radical polymerization. The as-synthesized polymer-clay nanocomposites exhibited enhanced Tg compared to pure polymer. TEM analysis revealed that after the dispersion of the clay, the prepared nanocomposite displayed a mixed nanomorphology with well-exfoliated silicate layers into the polymer matrix. The electrochemical measurements using polarization resistance, corrosion current, and impedance spectroscopy revealed that nanocomposites coatings with the low clay loadings (e.g., 1 wt%) exhibited better anticorrosion protection for steel compared to the pure poly(methyl methacrylate). In an independent study, the same group has also designed several nanocomposite materials containing polyaniline (PANI) and layered montmorillonite clay and investigated their corrosion performance for cold-rolled steel [55]. Firstly, the organophilic montmorillonite was prepared via cation-exchange reaction with cocamide-propylhydroxysultaine before being mixed with aniline monomers in diluted hydrochloric acid followed by one-step oxidative polymerization. TEM analysis of as-synthesized nanocomposite revealed that the prepared materials possessed mixed nanomorphology, and the silicate layers were found to be well dispersed in the polyaniline matrix. The electrochemical measurements of potentiodynamic (e.g., Tafel plots) of a series of polyaniline nanocomposites with varying clay loadings at room temperature are illustrated in **Table 3**. Electrochemical corrosion current values of polyaniline nanocomposites were found to be decreasing progressively with further increment in clay loading. Importantly, visual inspection of the corrosion products revealed the presence of grayish oxide layer formed over polyaniline nanocomposites, showing better corrosion performance. It is very important to stress that the incorporation of the montmorillonite in polyaniline matrix resulted in a decrease in mechanical strength and in thermal decomposition temperature. This could be attributed to the significantly decreased molecular weight of polyanilines formed in the montmorillonite. Same research group evaluated the effect of adding organo-modified clay on the corrosion protection performance of conducting polymer/layered silicate, such as poly(o-methoxyaniline) and poly(3-hexylthiophene) [56]. The experimental findings revealed that the conducting polymer/layered silicate nanocomposites with low clay loading (3 wt.%) were found exhibiting better anticorrosion properties compared to the pure conducting polymer.


The montmorillonite clay was firstly modified with quaternary or primary octadecylammonium cations before being mixed with the epoxy resin. The experimental findings revealed that the mechanical and thermomechanical of all epoxy-organoclay nanocomposites were enhanced compared to those of the pure epoxy polymer. The electrochemical impedance measurements indicated that the epoxy-montmorillonite clay modified with primary octadecylammonium cations exhibited better protection performance compared to those modified with quaternary octadecylammonium cations. Indeed, the total resistance value, *R*tot, after 4 days

ite made from modified clay with primary octadecylammonium ions. Importantly, the total resistance values decrease continuously in case of bare steel, with exposure time and the relation between these two factors were observed to be linear, indicating a constant corrosion rate. Importantly, the protective corrosion protection performance of the nanocomposite coatings was found to depend on the clay loading up to the saturation level. The excellent mechanical properties and thermal stability, as well as the high corrosion protection of these epoxy-clay nanocomposites, make them attractive candidates for various demanding coating applications. Al-Shahrani and colleagues demonstrated that the incorporation of modified bentonite with intercalating agents in the epoxy-based coatings resulted in the development of epoxybentonite nanocomposites with intercalated structures as shown in the **Figure 3** [62]. The presence of the silicate layers was evident in the TEM images with different degree of intercalation. The corrosion resistance abilities of a series of epoxy-bentonite nanocomposites, as coatings on carbon steel, were evaluated by electrochemical impedance spectroscopy, in 3.5% NaCl solution, at room temperature and compared to unpigmented epoxy. The experimental findings indicated that the presence of nanolayers has successfully improved the corrosion protection of epoxy resin as shown in **Table 4**. Furthermore, the amount of bentonite has an influence of the performance of the coating as the epoxy modified with 3% of bentonite led to

of bare steel, to 5.34 × 10<sup>3</sup>

) in the case of nanocompos-

in the case of epoxy-loaded with clay modified with

Polymer-Clay Nanocomposites for Corrosion Protection http://dx.doi.org/10.5772/intechopen.74154

(Ωcm2

in

71

exposure in the corrosive environment, improved from 1.03 × 102

**Figure 3.** TEM micrographs of epoxy/bentonite nanocomposites: 3% (left) and 5% (right).

quaternary octadecylammonium ions, and to 2.96 × 10<sup>4</sup>

the case of pure epoxy resin, to 7.40 × 10<sup>3</sup>

a As determined by thermogravimetric analysis.

b Saturated calomel electrode was employed as reference electrode.

**Table 3.** Relations of the composition of polyaniline (PANI)-MMT clay nanocomposite materials with the *E*corr, *R*p, *I*corr, and *R*corr measured from electrochemical methods<sup>a</sup> .

In a subsequent study, the same research group investigated the corrosion properties of polyaniline/clay nanocomposites prepared from Na<sup>+</sup> -montmorillonite or organo-modified montmorillonite with dodecylbenzene sulfonic acid using in-situ emulsion polymerization in the presence of aniline monomer [57]. The authors conducted a series of electrochemical measurements and concluded that the polyaniline nanocomposites coatings modified with low loading of Na<sup>+</sup> -montmorillonite exhibited better anticorrosion performance compared to conventional polyaniline on cold-rolled steel. This was attributed to the co-existence of the redox catalytic properties of polyaniline and the barrier effect of montmorillonite dispersed in the nanocomposites. Yeh and colleagues were also reported the anticorrosive properties of thermosetting polymer-layered silicate nanocomposites, such as polyimide and epoxy nanocomposites, prepared by solution dispersion procedure and thermal ring opening polymerization [58, 59]. The standard electrochemical measurements such as impedance spectroscopy, corrosion potential, and corrosion current revealed that the prepared thermosetting polymer/layered silicate nanocomposites exhibited enhanced protection against the corrosion on cold-rolled steel compared to bulk polymers. Danaee and co-workers investigated the effect of adding nanoclay on corrosion protection of zinc-rich epoxy coatings on steel [60]. The TEM findings revealed that the clay nanolayers were effectively dispersed and successfully separated between zinc particles in coating. The electrochemical measurements revealed that the incorporation of 1 wt.% clay enhanced the cathodic protection duration and sacrificial properties of the coatings. These findings clearly demonstrate that the incorporation of clay into the coating decreased the electrical contact between the zinc particles without affecting the zinc sacrificial properties. The authors indicated that high clay loadings lead to the increment of the porosity in coatings and the decrease in the intercalation of clay which could decrease the long-term protective performance of the coating. Spathis and co-workers investigated the performance of epoxy-clay nanocomposite coatings for steel protection [61]. The montmorillonite clay was firstly modified with quaternary or primary octadecylammonium cations before being mixed with the epoxy resin. The experimental findings revealed that the mechanical and thermomechanical of all epoxy-organoclay nanocomposites were enhanced compared to those of the pure epoxy polymer. The electrochemical impedance measurements indicated that the epoxy-montmorillonite clay modified with primary octadecylammonium cations exhibited better protection performance compared to those modified with quaternary octadecylammonium cations. Indeed, the total resistance value, *R*tot, after 4 days exposure in the corrosive environment, improved from 1.03 × 102 of bare steel, to 5.34 × 10<sup>3</sup> in the case of pure epoxy resin, to 7.40 × 10<sup>3</sup> in the case of epoxy-loaded with clay modified with quaternary octadecylammonium ions, and to 2.96 × 10<sup>4</sup> (Ωcm2 ) in the case of nanocomposite made from modified clay with primary octadecylammonium ions. Importantly, the total resistance values decrease continuously in case of bare steel, with exposure time and the relation between these two factors were observed to be linear, indicating a constant corrosion rate. Importantly, the protective corrosion protection performance of the nanocomposite coatings was found to depend on the clay loading up to the saturation level. The excellent mechanical properties and thermal stability, as well as the high corrosion protection of these epoxy-clay nanocomposites, make them attractive candidates for various demanding coating applications. Al-Shahrani and colleagues demonstrated that the incorporation of modified bentonite with intercalating agents in the epoxy-based coatings resulted in the development of epoxybentonite nanocomposites with intercalated structures as shown in the **Figure 3** [62]. The presence of the silicate layers was evident in the TEM images with different degree of intercalation. The corrosion resistance abilities of a series of epoxy-bentonite nanocomposites, as coatings on carbon steel, were evaluated by electrochemical impedance spectroscopy, in 3.5% NaCl solution, at room temperature and compared to unpigmented epoxy. The experimental findings indicated that the presence of nanolayers has successfully improved the corrosion protection of epoxy resin as shown in **Table 4**. Furthermore, the amount of bentonite has an influence of the performance of the coating as the epoxy modified with 3% of bentonite led to

**Figure 3.** TEM micrographs of epoxy/bentonite nanocomposites: 3% (left) and 5% (right).

In a subsequent study, the same research group investigated the corrosion properties of

**Table 3.** Relations of the composition of polyaniline (PANI)-MMT clay nanocomposite materials with the *E*corr, *R*p, *I*corr,

.

montmorillonite with dodecylbenzene sulfonic acid using in-situ emulsion polymerization in the presence of aniline monomer [57]. The authors conducted a series of electrochemical measurements and concluded that the polyaniline nanocomposites coatings modified with

to conventional polyaniline on cold-rolled steel. This was attributed to the co-existence of the redox catalytic properties of polyaniline and the barrier effect of montmorillonite dispersed in the nanocomposites. Yeh and colleagues were also reported the anticorrosive properties of thermosetting polymer-layered silicate nanocomposites, such as polyimide and epoxy nanocomposites, prepared by solution dispersion procedure and thermal ring opening polymerization [58, 59]. The standard electrochemical measurements such as impedance spectroscopy, corrosion potential, and corrosion current revealed that the prepared thermosetting polymer/layered silicate nanocomposites exhibited enhanced protection against the corrosion on cold-rolled steel compared to bulk polymers. Danaee and co-workers investigated the effect of adding nanoclay on corrosion protection of zinc-rich epoxy coatings on steel [60]. The TEM findings revealed that the clay nanolayers were effectively dispersed and successfully separated between zinc particles in coating. The electrochemical measurements revealed that the incorporation of 1 wt.% clay enhanced the cathodic protection duration and sacrificial properties of the coatings. These findings clearly demonstrate that the incorporation of clay into the coating decreased the electrical contact between the zinc particles without affecting the zinc sacrificial properties. The authors indicated that high clay loadings lead to the increment of the porosity in coatings and the decrease in the intercalation of clay which could decrease the long-term protective performance of the coating. Spathis and co-workers investigated the performance of epoxy-clay nanocomposite coatings for steel protection [61].



**Electrochemical corrosion measurementsb**

*I***corr <sup>×</sup> <sup>10</sup>**

**−6 (A/cm2**

**)** *R***corr (mm/year)**

**cm2 )**

polyaniline/clay nanocomposites prepared from Na<sup>+</sup>

Saturated calomel electrode was employed as reference electrode.

low loading of Na<sup>+</sup>

**Compound code**

a

b

**Feed composition** 

70 Current Topics in the Utilization of Clay in Industrial and Medical Applications

As determined by thermogravimetric analysis.

and *R*corr measured from electrochemical methods<sup>a</sup>

**Inorganic content found in the product (wt%)a**

**PANI MMT** *E***corr (v)** *R***p (KΩ** 

Bare — — — −0.641 0.8 44.4 86.1 PANI 100 0 0 −0.590 3.4 12.0 23.3 CLAN0.25 99.75 0.25 0.70 −0.581 13.7 2.9 5.6 CLAN0.5 99.25 0.50 1.50 −0.568 15.4 2.7 5.2 CLAN0.75 99.00 0.75 3.80 −0.555 20.0 2.4 4.5 CLAN1 99.00 1.00 4.70 −0.551 36.2 1.1 2.1 CLAN3 97.00 3.00 7.10 −0.543 57.9 0.5 1.0

**(wt.%)**


**Table 4.** The resistance and capacitance of coated samples from electrochemical impedance spectroscopy calculations after 40 days of immersion.

a high protection level. 5 wt% clay loading showed the lowest performance, indicating that it exceeded the saturation level of clay into the epoxy and consequently generated areas of agglomeration that can be identified as weaknesses in the coating. Such findings suggest that there is a critical loading value above which the coating might be affected [63, 64].

Navarchian and co-workers prepared polyaniline and polyaniline/montmorillonite nanocomposites via in-situ oxidative polymerization, and the resulted nanoparticles were incorporated into the epoxy resins and coated on steel substrates [65]. The anticorrosion performance of prepared epoxy-based coatings was conducted through electrochemical Tafel and electrochemical impedance spectroscopy tests. It was reported that the epoxy coating modified by polyaniline/montmorillonite nanocomposite particles exhibited improved corrosion protection compared to unpigmented epoxy and epoxy/polyaniline coatings as it can be seen in **Table 5**. Furthermore, these findings indicated also that the incorporation of polyaniline and organo montmorillonite (OMMT) into epoxy coating improves its anticorrosion performance compared to polyaniline/montmorillonite and neat polyaniline. Similar findings were reported by Kalaivasan and Shafi using polyaniline/montmorillonite clay nanocomposites prepared by mechanochemical intercalation method [66].

raw Na<sup>+</sup>

a

b

**Compound code**

**Feed composition** 

As determined by thermogravimetric analysis.

measured by electrochemical methods.

Saturated calomel electrode was employed as reference electrode.

**Inorganic content found in the product (wt.%)a**

**PMBS MMT** *E***corr (v)** *R***p (KΩ** 

Bare — — **—** −0.670 1.91 80.00 37.24 PMBS 100 0 4.56 −0.644 13.87 31.40 14.62 CLMA1 99.00 1.00 6.13 −0.568 20.86 11.60 5.40 CLMA3 97.00 3.00 7.05 −0.528 67.36 10.20 4.75 CLMA3 (M) 97.00 3.00 7.28 −0.575 50.33 15.20 7.08

**(wt.%)**

latexes with Na<sup>+</sup>

**7. Concluding remarks**


as corrosion potential, polarization resistance, corrosion current corrosion rate, and electrochemical impedance spectroscopy, the nanocomposite coating containing 1 wt% of clay exhibited an noticeable improved corrosion efficiency on cold-rolled steel electrode at high temperature of 50°C and was found even much better than that of no coated and electrode coated with unpigmented polyaniline at room temperature. Indeed, the Ecorr of polyaniline nanocomposites measured at 50°C (*E*corr = −572.5 mV) was lower than that of uncoated

**Table 6.** Relations of the composition of polyacrylate-latex clay nanocomposite materials with the *E*corr, *R*p, *I*corr, and *R*corr

Yeh and colleagues recently reported the anticorrosive properties of water-based polyacrylate/

lonite clay were used for the preparation of nanocomposites. The anticorrosion performance of cold-rolled steel coupons coated with as-prepared unpigmented polyacrylate (denoted PMBS) and a series of nanocomposite latexes were evaluated by operating sequential electrochemical corrosion parameters, such as corrosion potential, polarization resistance, corrosion current, and corrosion rate as illustrated in **Table 6**. It should be noted that nanocomposite

In conclusion, an impressive progress has been reported during the last few years regarding the preparation and the use of polymer-clay nanocomposites for corrosion protection. These materials offer a number of advantages, such as excellent mechanical and thermal stability, improved anticorrosion protection, and wide accessibility of clay. The corrosion protection properties of these materials were found influenced by the type of the clay and curing agents



**Electrochemical corrosion measurementsb**

*I***corr × 10−6 (A/ cm2 )**

Polymer-Clay Nanocomposites for Corrosion Protection http://dx.doi.org/10.5772/intechopen.74154

*R***corr (mm/year)**

73

**cm2 )**

corr, *R*corr, and *R*ct.

(*E*corr = −664.1 mV) and polyaniline-coated electrode measured at room temperature.

coupons than that of with organo-MMT clay based on the studies of *E*corr, *R*p, *I*

layered silicate nanocomposites [68]. Raw Na<sup>+</sup>

It is worth noting that the effect of clay in the polymer/layered silicate nanocomposites coatings was commonly evaluated at room temperature, and the investigation of the corrosion performance of these materials at higher temperature has attracted little attention. Do the coatings operated at high temperatures still maintain their good corrosion efficiency as even compared to that of electrode coated with neat polymer at room temperature? In this context, Yeh and colleagues performed the electrochemical corrosion parameter measurements of water-based conducting polyaniline/montmorillonite nanocomposites of polyaniline with


**Table 5.** The Tafel plot data for steel panels coated with neat and modified epoxy in NaCl (3.5 wt. %) solution.


a As determined by thermogravimetric analysis.

a high protection level. 5 wt% clay loading showed the lowest performance, indicating that it exceeded the saturation level of clay into the epoxy and consequently generated areas of agglomeration that can be identified as weaknesses in the coating. Such findings suggest that

**Table 4.** The resistance and capacitance of coated samples from electrochemical impedance spectroscopy calculations

Navarchian and co-workers prepared polyaniline and polyaniline/montmorillonite nanocomposites via in-situ oxidative polymerization, and the resulted nanoparticles were incorporated into the epoxy resins and coated on steel substrates [65]. The anticorrosion performance of prepared epoxy-based coatings was conducted through electrochemical Tafel and electrochemical impedance spectroscopy tests. It was reported that the epoxy coating modified by polyaniline/montmorillonite nanocomposite particles exhibited improved corrosion protection compared to unpigmented epoxy and epoxy/polyaniline coatings as it can be seen in **Table 5**. Furthermore, these findings indicated also that the incorporation of polyaniline and organo montmorillonite (OMMT) into epoxy coating improves its anticorrosion performance compared to polyaniline/montmorillonite and neat polyaniline. Similar findings were reported by Kalaivasan and Shafi using polyaniline/montmorillonite clay nanocomposites

It is worth noting that the effect of clay in the polymer/layered silicate nanocomposites coatings was commonly evaluated at room temperature, and the investigation of the corrosion performance of these materials at higher temperature has attracted little attention. Do the coatings operated at high temperatures still maintain their good corrosion efficiency as even compared to that of electrode coated with neat polymer at room temperature? In this context, Yeh and colleagues performed the electrochemical corrosion parameter measurements of water-based conducting polyaniline/montmorillonite nanocomposites of polyaniline with

**)** *E***corr × 103**

**Table 5.** The Tafel plot data for steel panels coated with neat and modified epoxy in NaCl (3.5 wt. %) solution.

**(v)** *R***p (KΩ cm<sup>2</sup>**

**)** *R***corr (mm/year)**

**) Capacitance (F)**

there is a critical loading value above which the coating might be affected [63, 64].

Neat epoxy 5.60 4.00E-04 Epoxy and 1 wt.% clay nanocomposites 4.5E + 05 1.04E-10 Epoxy and 3 wt.% clay nanocomposites 5.60E + 05 9.65E-11 Epoxy and 5 wt.% clay nanocomposites 1.60E + 05 5.00E-10

**Coatings systems Resistance (KΩ.cm<sup>2</sup>**

72 Current Topics in the Utilization of Clay in Industrial and Medical Applications

prepared by mechanochemical intercalation method [66].

 **(A/cm2**

Epoxy 1.170 −483 11.35 0.013 Epoxy/PANI 0.798 −463 17.24 0.009 Epoxy/PANI/MMT 0.651 −459 19.97 0.007 Epoxy/PANI/OMMT 0.467 −418 28.51 0.005

**Sample code** *I***corr × 106**

after 40 days of immersion.

b Saturated calomel electrode was employed as reference electrode.

**Table 6.** Relations of the composition of polyacrylate-latex clay nanocomposite materials with the *E*corr, *R*p, *I*corr, and *R*corr measured by electrochemical methods.

raw Na<sup>+</sup> -montmorillonite clay [67]. In this study and based on the electrochemical tests such as corrosion potential, polarization resistance, corrosion current corrosion rate, and electrochemical impedance spectroscopy, the nanocomposite coating containing 1 wt% of clay exhibited an noticeable improved corrosion efficiency on cold-rolled steel electrode at high temperature of 50°C and was found even much better than that of no coated and electrode coated with unpigmented polyaniline at room temperature. Indeed, the Ecorr of polyaniline nanocomposites measured at 50°C (*E*corr = −572.5 mV) was lower than that of uncoated (*E*corr = −664.1 mV) and polyaniline-coated electrode measured at room temperature.

Yeh and colleagues recently reported the anticorrosive properties of water-based polyacrylate/ layered silicate nanocomposites [68]. Raw Na<sup>+</sup> -montmorillonite clay and organo montmorillonite clay were used for the preparation of nanocomposites. The anticorrosion performance of cold-rolled steel coupons coated with as-prepared unpigmented polyacrylate (denoted PMBS) and a series of nanocomposite latexes were evaluated by operating sequential electrochemical corrosion parameters, such as corrosion potential, polarization resistance, corrosion current, and corrosion rate as illustrated in **Table 6**. It should be noted that nanocomposite latexes with Na<sup>+</sup> -MMT clay exhibit better corrosion protection efficiency on cold-rolled steel coupons than that of with organo-MMT clay based on the studies of *E*corr, *R*p, *I* corr, *R*corr, and *R*ct.
