Anticorrosion coatings conducting polymers

Probable applications in various fields like electro chromic displays, electronic devices, modified electrodes, chemical- and bio-sensors etc. [ 133] may be envisaged. Potentially, nanodimensional oxide- (Si02, Mn02 and Zr02) based composites of these polymers have shown promise as optical materials [50]. Conducting polymer-coated low Tg latexes of sub-micron (50-500 nm) dimensions are reported to find use in antistatic and anticorrosion applications [ 113]. In the light of this information it would be of interest to explore the usability of the corresponding MMT-based composites in these directions. 

Nanostructured Conducting-Polymer Coatings and Anticorrosion Protection... 

E. Armelin, R. Oliver, F. Liesa, J.I. Iribarren, F. Estrany, and C. Aleman, Marine paint formulations conducting polymers as anticorrosive additives. Prog. Org. Coatings, 59,46-52 (2007). 

A conductive polymer film of polypyrrole doped with polymolybdate anions was electrodeposited onto steel and found to provide corrosion protection in neutral and acidic 3.5% NaCl solution [152]. The anodic codeposition of polypyrrole and Ti02 onto mild steel in an oxalic acid medium has been described [153,154]. The PPy and Ti02 composite showed a considerable improvement in anticorrosion properties with respect to PPy films in salt spray and weight-loss tests. It was suggested that these composite films could be applied as a primary coating replacement for the phosphatized layers on mild steel [154]. 

Aeiyach, S., et al. 2003. Conjugated organic polymers for anticorrosion coating. ACS Symposium Series 832 (Conducting Polymers and Polymer Electrolytes), 128. 

Conductive polymer nanocomposites may also be used in different electrical applications such as the electrodes of batteries or display devices. Linseed oil-based poly(urethane amide)/nanostuctured poly(l-naphthylamine) nanocomposites can be used as antistatic and anticorrosive protective coating materials. Castor oil modified polyurethane/ nanohydroxyapatite nanocomposites have the potential for use in biomedical implants and tissue engineering. Mesua ferrea and sunflower seed oil-based HBPU/silver nanocomposites have been found suitable for use as antibacterial catheters, although more thorough work remains to be done in this field. ° Sunflower oil modified HBPU/silver nanocomposites also have considerable potential as heterogeneous catalysts for the reduction of nitro-compounds to amino compounds. Castor oil-based polyurethane/ epoxy/clay nanocomposites can be used as lubricants to reduce friction and wear. HBPU of castor oil and MWCNT nanocomposites possesses good shape memory properties and therefore could be used in smart materials. ... 

Intrinsically conducting polymers (ICPs) are electroactive long-range conjugated polymers. They generally possess reversible redox performance, while metal corrosion is also a redox process therefore, it is possible that ICPs may find application for metal anticorrosion. It is true since the early report for corrosion inhibition performance of ICPs such as polyaniline (PANI) by DeBerry [5]. After more than 20 years of development, now ICPs have received much attention, since th may be a kind of alternative anticorrosion agents instead of the toxic heavy metal in anticorrosion coating, no matter they are used alone or as composite with substrate resin. 

Common matrix resins for blending with conducting polymers are widely used in traditional anticorrosion coatings, such as epoxy resin [25, 27, 32, 34, 68, 70, 71, 76], polyacrylic-based resin [24, 39, 48, 77, 78], and poly(methyl methacrylate) [30, 60, 62, 64]. The feature of matrix resin as well as the amount of ICPs is important to the anticorrosion performance of conductive composite coating. Samui and Phad-nis [67] blended various amounts of dioctyl phosphate (DOPH)-doped PANI with different polymeric matrices (epoxy resin, polyurethane resin, styrene-butyl acrylate... 

The results were positive and promising. Bagherzadeh et al. [81] found that the anticorrosion performance of a two-component water-based epoxy resin coating system was improved by adding only 0.02 wt% nano-PANI. Ahmad et al. [82] investigated the corrosion protection behavior of waterborne resorcinol formaldehyde (RF)-cured composite coatings of poly(l-naphthylamine) (PNA)/poly(vinyl alcohol) (PVA) on mild steel, and even superior corrosion protective performance was observed in different corrosive media when compared with the reported solvent-based conductive polymer coatings. 

A great deal of research has been carried out to develop anticorrosion primers. Reviews of studies of the mechanism of corrosion protection by conductive polymer coatings often yield quite confusing information that is not yet fully understood. In general, it can be said that conductive polymers offer anticorrosive properties by a combination of the following hypothesis ... 

Corrosion protection by ICPs has been well documented in several reviews [136-141]. The use of ICP-based core-shell latexes for the corrosion protection of steel is a relatively new field of research, and a recent review has proposed the exploitation of such possibihties [142]. In a recent study, we found that ICP-based core-shell latexes offer the possibility of achieving anticorrosion properties [143], though the presence of pinholes or scratches in the coatings enhances the corrosion rate of metals. This problem may be due to poor dispersion of the composite particles in the insulating resin systems, and future research will need to develop conductive polymer-based anticorrosive primers for metals. The anticorrosive properties of PANI-coated polystyrene latex microspheres has been reported recently [144]. PS-PANI composite particles with core-shell structure were prepared by chemical oxidative polymerization of anihne monomer in the presence of a PVP-stabilized PS latex suspension. The reduced form of the particle was obtained by adding hydrazine mono hydrate to the suspension. Both oxidized and reduced PANI-PS particles were used to obtain a PANI-PS-coated iron electrode (PANl-PS-Fe). Pure PANI... 

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