Polypyrrole protective coatings

Oxide, flouride, and polymeric films, as well as certain others, are used as protective coatings for HTSC materials (for example, see [505]). The electrodeposition of conducting polymers such as polypyrrole [433,491, 493, 506], polythiophene and its derivatives [493, 507], and polyaniline [478] is the most effective process. Anodic electropolymerization in acetonitrile solutions proceeds without any degradation of the HTSC substrate and ensures continuous and uniform coatings. Apparently, this method is promising not only for the fabrication of compositions with special properties based on HTSC [50, 28,295] as mentioned above, but also for the creation of junctions with special characteristics [507]. 

J.-M. Yeh, C.-P. Chin and S. Chang, Enhanced corrosion protection coatings prepared from soluble electronically conductive polypyrrole-clay nanocomposite material, J. Appl. Polym. Sci, 88, 3264-3272 (2003). 

H. Nguyen Thi Le, M.C. Bernard, B. Garcia-Renaud, and C. Deslouis, Raman spectroscopy analysis of polypyrrole films as protective coatings on iron, Synth. Metals, 140,287-293 (2004). 

FIGURE 14.3 Corrosion protective efficiency of PPy/DGEBA in (a) HCl, (b) NaOH, and (c) NaCl media. (Reprinted from Prog. Org. Coat., 59, Riaz, U. et al. High Performance Corrosion Protective DGEBA/ Polypyrrole Composite Coatings, 138, Copyright 2007, with permission from Elsevier.)... 

Riaz, U, Ashraf, SM, Ahmad, S. 2007. High Performance Corrosion Protective DGEBA/Polypyrrole Composite Coatings. Prog. Org. Coat., 59,138. 

Electrosynthesized composites of poly(l,5-diaminonaphthalene) with polyaniline [146] and with polypyrrole [147] have been described and are reported to offer improved corrosion protection of iron. The corrosion-resistant properties of polyaniline and polypyrrole composite coatings electrochem-ically deposited on low carbon steel [148] were found to be strongly influenced by the applied potential and molar feed ratio of the monomers. 

Deslouis, C., B. Garcia-Renaud, and N.T. Le Hien. 2001. Composite oxide/cp or large size anions/cp films as active protective coatings. Case of polypyrrole. Proc Electrochem Soc 2001-22 (Corrosion and Corrosion Protection), 596. 

Truong, V.T., et al. 2000. Corrosion protection of magnesium by electroactive polypyrrole/paint coatings. Synth Met 110 (1) 7. 

Shah, K., et al. 2001. Corrosion protection properties of polyaniline-polypyrrole composite coatings on Al 2024. Surf Eng 17 (5) 405. 

Ferreira, C.A., et al. 1999. Appraisal of the polypyrrole/cataphoretic paint bilayer system as a protective coating for metals. Appl Electrochem 29 (2) 259. 

Yeh J. M., Chin C. P. and Chang S. (2003), Enhanced Corrosion Protection Coatings Prepared from Soluble Electronically Conductive Polypyrrole-clay Nanocomposite Materials. JAppl Polym Sci, 88, 3264-72. 

This diol was mixed with other diols, then reacted with diisocyanates to form polyurethanes. The electrically conducting polymers, polyaniline and polypyrrole, prevent corrosion of steel.105 One of the best formulations uses polyaniline with zinc nitrate, which is then covered with an epoxy resin topcoat. Polyorganosiloxanes have been grafted to starch using the sol-gel method with alkoxysi-lanes. These materials have been complexed with cerium ions to provide corrosion protection for aircraft that is expected to be 50% cheaper than conventional coatings.106... 

Thin films of conductive polymers like polypyrrole, polyaniline, etc are also used for the surface modification of the semiconductor electrodes [26, 27]. Their performance mechanism has not yet been deciphered. Most likely, the coating is a combination of a protective film and the charge carrier, the more so that reversible redox couples are used to be introduced into films [28], as well as catalytically-active admixtures like Ru02 [29]. Such films were used to stabilize a promising "solar" electrode material, amorphous silicon [30]. 

An example of the protective value of polypyrrole is to be found in the work of Skotheim et al (43) who stabilized n-Si with thin films of this material. These conductive films were photo-electrochemically generated and they extended the operational lifetime of illuminated n-Sl from about four hours to 6 days in the presence of l2 /I couple in aqueous solution. The cell showed no decay after running continuously at anodic current densities of 9 ma/cm2 for this long period. Noufl et al (42) found similar enhanced stability of n-Si coated with polypyrrole in the presence of the Fe3+/2+ couple, and for n-GaAs in CH3CN solutions (45). 

N.V. Krstaijic, B.N. Grgur, S.M. Jovanovic and M.V. Vojnovic. Corrosion protection of mild steel by polypyrrole coatings in acids sulfate solutions. Electrochem. Acta, 1997, Vol. 42, No. 11, pp. 1685-1691. 

Figure 16.8 Representation of the coated iron sample (PPy + top-coat) and its defect in contact with KCI solution. Delamination is followed by SKP measurements. (Reprinted with permission from Corrosion Science, On the development of polypyrrole coatings with seifhealing properties for iron corrosion protection by G. Paliwoda-Porebska, M. Stratmann, M. Rohwerder et al., 47, 12, 3216-3233. Copyright (2005) Elsevier Ltd)...

Figure 16.10 OCP curves of coated PPy zinc electrodes cured In air for 1 h at 180 °C and immersed in 3.5% NaCI solution. PPy films (Ri2iim thick) were synthesized in 2 M NaSac+ 0.5 M Py at pH 5 and 1.9 M NaSac + 0.1 M DISacH + 0.5 M Py at pH 5.4. (Reprinted with permission from Chemistry of Materials, Ultrafast electrosynthesis of high hydrophobic polypyrrole coatings on a Zinc electrode Applications to the protection against Corrosion by E. Hermelin,]. Petitjean, P.C. Lacaze et al., 20, 13, 4447—4456. Copyright (2008) Elsevier Ltd)...

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