Polyaniline anticorrosive coatings

In the meantime, parallel product development toward commercially useful and competitive anticorrosion coating systems has led to various products finding their place in the market, having been successfully tested under practical and various laboratory conditions [74]. It also became evident that the conclusions that were drawn from the basic research on dispersion and the corrosion prevention mechanism of polyaniline have led to superior performance compared to other systems, which have been proposed as alternative techniques [75,114a,114b,l 14c]. This is probably due to the fact that the alternative methods do not fulfill all chemical, physical, and technical requirements that a corrosion prevention technology based on polyaniline on a technical scale has to. 

Tiitu, M., et al. 2005. Aminic epoxy resin hardeners as reactive solvents for conjugated polymers Polyaniline base/epoxy composites for anticorrosion coatings. Polymer 46 (18) 6855. 

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. 

A. Kalendova, D. Vesely, J. Stejskal, andM. Trehova, Anticorrosion properties of inorganic pigments surface-modified with a polyaniline phosphate layer. Prog. Org. Coatings, 63, 209-221 (2008). 

A. Meroufel, C. Deslouis, and S. Touzain, Electrochemical and anticorrosion performances of zinc-rich and polyaniline powder coatings, Electrochim. Acta, 53, 2331 2338... 

It was only in 1992-1993 that we finally found out after an in-depth evaluation of the interactions between various metal surfaces and coatings of polyaniline (applied as pure dispersion or as dispersion paints) that together with a remarkable corrosion potential shift (ermobling) and an iron oxide layer formation (passivation) lead to a significant anticorrosion effect [71]. In a study together with Elsenbaumer et al. [72], we discovered that the corrosion rate was reduced by a factor of up to 10,000. The iron oxide that formed between the metal surface and the polyaniline primer coating was determined to be Fe203, later confirmed with even clearer x-ray photoelectron spectra (XPS) [23b]. 

Figure 10.6 Test coating of anticorrosion polyaniline coating on a 2000 ton container ship. The coating is still effective till now since December 2005.

Adhikari, A., Claesson, P., Pani,)., Leygraf, C., Deidinaitei, A., and Blomberg, E. (2008) Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel. Bectrochim. Acta, 53,4239-4247. 

Chang, K.-C., Jang, G.-W, Peng, C.-W., Lin, C.-Y, Shieh, J.-C., Yeh, J.-M., Yang, J.-C and Li, W.-T. (2007) Comparatively electrocherrucal studies at different operational temperatures for the effect of nanoclay platelets on the anticorrosion efficiency of DBSA-doped polyaniline/Na -MMT clay nanocomposite coatings. Electrochim. Acta, 52, 5191-5200. 

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