Doping corrosion inhibition

L. Mascia, L. Prezzi, G. D. Wilcox and M. Lavorgna, Molybdate doping of networks in epoxy-silica hybrids domain structuring and corrosion inhibition, Prog. Org. Coat., 2006, 56, 13. 

R., and Medraj, M. (2014) In-vitro corrosion inhibition mechanism of fluorine-doped hydroxyapatite and brushite coated Mg-Ca alloys for biomedical applications. Ceram. Int, 40 (6), 7971-7982. 

In many applications, moderate to high electrical conduction is required to serve the purpose. In such systems, it is preferred to prepare ICPs-based BLNs or CMPs/NCs/HYBs by incorporation of highly doped forms (or ICPs) inside a variety of polymeric hosts (thermoplasts, thermosets, rubber, elastomer). Many a times, ICPs-based copolymers have also been made to optimize the conductivity, processability, electroactivity, and optoelectronic properties. These copolymers are widely employed in the areas like corrosion inhibition, EMI shielding, ECs, gas sensing, biosensing, energy storage, thermoelectric, antistatics, etc. 

Ogurtsov, N.A., et al. 2004. Corrosion inhibition of aluminum alloy in chloride mediums by undoped and doped forms of polyaniline. Synth Met 143 (1) 43. 

Visual observations and spectroscopic investigations on the various aluminum alloys coated with doped polyaniline and doped polypyrrole indicate that there is no long-range electrode polarization phenomenon like that observed on mild steel-coated samples. The corrosion protection of aluminum using conducting polymers is affected by the composition of the aluminum alloy. Corrosion inhibition is controlled solely by anodic protection. Doped polyaniline coatings provide better corro-... 

The plethora of data presented in this chapter and in the literature leaves no doubt that corrosion processes and mechanisms for inhibition are complex. Nonetheless, it is well established that conductive polymers can impart significant corrosion protection to selected metals such as steel, aluminum, and copper. Also, a picture is beginning to emerge of the corrosion inhibition mechanisms that rationalizes the observations made on corroding cold steel coated with polyaniline. For this system there are two cases to consider. Case I is where a steel surface exposed to a corrosive environment is completely covered by a coating of doped polyaniline. Case II is a case where a steel surface exposed to a corrosive environment is almost completely covered by a coating of doped polyaniline but also has small areas of bare steel exposed. 

The overall mechanism for corrosion inhibition for this case is simplistically illustrated in Fig. 31.40. Wes-sling [20] and Lu et al. [26,29] clearly demonstrated that when doped polyaniline is placed in contact with mild steel, the steel surface undergoes a rapid oxidation process to provide a layer of y-Fe203 at the polyaniline/ iron interface. This process is shown schematically in Fig. 31.40 by the transformation of (a) to (b) and occurs according to the equation... 

Fig. 31.40 Schematic illustration of the mechanism of corrosion inhibition provided by doped polyaniline on steel with no defects in the coating.

The mechanism of corrosion inhibition using the Ce-doped cation-exchange pigment is presented in Fig. 2.7. The pigment keeps entrapped inhibiting cations... 

An extensive study on anticorrosion properties of PANI, PPy and PEDOT used as additives was reported in [88]. Results indicate that the protection against corrosion imparted by the formulations modified by the addition of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulphonate), PANI-ES and, especially, PANI-EB is significantly higher than that of the unmodified epoxy paint. Thus, results evidence that some CP compositions can inhibit the steel corrosion and, therefore, small concentrations of these materials would be used to replace conventional inorganic corrosion inhibitors currently used in primer paints. In Table 10.6, some examples of the... 

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