Corrosion prevention, polyanilines

B. Wessling, Corrosion Prevention with an Organic Metal (Polyaniline) Surface Ennobling, Passivation, Corrosion Test Results. Mater. Corros. Korros. 1996,47,439-445. 

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. 

Jasty, S., and A.J. Epstein. 1995. Corrosion prevention capability of polyaniline (emeraldine base and salt) An XPS study. Polym Mater Sci Eng 72 565. 

Samui, A.B., et al. 2003. Study of polyaniline containing paint for corrosion prevention. Prog Org Coat 47 (1) 1. 

Berry, B.C., A.U. Shaikh, and T. Viswanathan. 2003. Lignosulfonic acid-doped polyaniline (ligno-pani) for the corrosion prevention of cold-rolled steel. In Electroactive polymers for corrosion control, eds. P. Zarras, J.D. Stenger-Smith, and Y. Wei, 182. Washington DC American Chemical Society. 

Wessling, B. (1996) Corrosion prevention with an organic metal (polyaniline) surface ennobling, passivation, corrosion test results. Werkst. Korros. (Mater. Corros.), A7, 439-445. 

For over a decade, the use of poly aniline for corrosion protection of metals, particularly stainless steel, has been investigated. In the first study [105] by DeBerry, polyaniline was electrochemically deposited on ferritic stainless steels and found to provide anodic protection that significantly reduced corrosion rates in acid solutions. Numerous studies since then have confirmed the corrosion-preventing properties of polyanilines [102-104,106-111]. In addition, nonelectrochemical methods of applying polyaniline have been demonstrated [102-104,106-1111. In one recent study (I09J, dispersions based on doped polyaniline. Versicon, ... 

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... 

Polyaniline s metallic character, its position just below silver towards the noble-metal end of the electromotive force series, and its redox behaviour mentioned above, also make it possible to use a polyaniline coating to protect metals against corrosion. Our investigations show that the plastic removes electrons from the metal and is thereby reduced, while iron, for example, is oxidised to Fe203, This oxide layer is not rust (which consists of a loose mixture of various oxides and hydroxides), but functions as a protective passivating layer, in other words prevents further... 

Thompson and coworkers (83,90] found a reduction in corrosion in samples of steel that had been coated with neutral polyaniline (EB) and exposed to a salt solution (3.5% NaCI) and an acid environment (0.1 N HCl) after doping" and applying a top coat. They found, however, that they were able to achieve good corrosion protection with only certain dopants moreover, adhesion problems prevented them from obtaining reproducible and acceptable results. 

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