The corrosion of metal is an electrochemical phenomenon, and Polymer Alloys LLC, a New York-based startup, owns the IP (intellectual property) rights to several embryonic corrosion protection technologies that have an electrochemical basis. Moreover, these technologies employ corrosion inhibitors that do not contain toxic heavy metals, such as hexavalent chromium.

             Some of these IP assets relate to the use of known polymer compositions for the corrosion protection of metal --- one is commercially available; the other is still at a more embryonic stage in its development. The other IP assets deal with the use of structurally related, but commercially available small molecules to the second polymer, as the corrosion inhibitor component.

             The first Polymer Alloys IP asset concerns the use of polyphenylene ether¹ , "PPE", (which is also called "polyphenylene oxide") as a thin primer or wash coat treatment to corrosion protect such metals as iron, steel, aluminum or copper. This particular technology may be of interest to the metal finishing industry, in particular, since PPE resin does not contain any potentially toxic heavy metal, such as chromium. Current practice widely employs hexavalent chromium in metal conversion coatings, and there is substantial pressure to either reduce or eliminate its use for environmental reasons.

             Polymer Alloys' patented use of PPE is covered in U.S. Patent No. 6,004,628² (Dec. 21, 1999) and in pending counterpart applications in Canada, Japan and the European Patent Office. The technology, while still embryonic and in need of further development, involves the formation of a thin (e.g., about 0.2 mil or less) coating of PPE on a metal surface that has not yet been treated with a conversion coating (for example, a chromate conversion coating). The application of this wash coat is then followed by the optional, but highly preferred, application of a protective polymer topcoat (e.g., such as polyurethane). While an earlier, rather obscure, but patented³ , development by a Czechoslovakian group had indicated that PPE does not adequately adhere to metal without the presence of an underlying conversion coating, the Polymer Alloys work illustrates that a properly applied, thin wash coat layer of PPE has both good adhesion as well as positive corrosion protection effect for the underlying metal.

             The technology of using a PPE wash coat is broadly applicable to any metal substrate, including steel or aluminum, and could find wide use in the metal production and metal finishing industry, assuming the experimental results described in the patent document are verified upon scale-up. A very positive attraction to using PPE, rather than inorganic chromates, in the initial treat metal substrates is the rather benign toxicological profile for PPE -- it is believed to be a food grade material for many end use applications.

             The patent document, in its Example 2, suggests a growth in the polymer's molecular weight after its application to the metal substrate, as compared to the molecular weight for the resin apart from the metal. It is believed that PPE may act in an electrochemical (or redox) manner when brought into contact with metal and that this mode of action somehow causes the interesting molecular weight data described in the patent.

             While Polymer Alloys has created a potential new market use for the well-established PPE resin, it has also created another new use for a less used resin --- polyaniline⁴. Our U.S. Patent No. 5,928,795 (July 27, 1999) covers the use of the undoped (or "emeraldine base" form) of polyaniline on aluminum ("PANI-EB") as a corrosion protection agent. While prior investigators of the use of polyaniline as a metal corrosion protection agent have focused on the acid-doped, more conductive versions of that polymer, the Polymer Alloys approach uses the undoped version that is free of potentially migratory acidic dopants which had hitherto been believed to be necessary⁵ . Interestingly, the data in the patent indicate that the use of the PANI-EB corrosion protection coating bonds appears to bond more tenaciously to aluminum after a room temperature cure (e.g., 98%-99%) than to steel (e.g., only 75%-88%). This particular aluminum protection technology may be attractive to the aerospace, automotive, construction, and container industries that utilize large amounts of aluminum.

             The PANI-EB material is also believed by many in the field to act in an electrochemical (or redox) manner when brought into contact with a metal substrate.

             The next technology area in the Polymer Alloys collection relates to the use of para-phenylenediamine rubber antidegradants in an organic coating (e.g., in a paint coating) on metal to protect the metal substrate from corrosion⁶. Compounds of this type contain a p-phenylenediamine structure (-NHC6H4NH-) as a basic backbone structure. We view them lower molecular weight analogs of PANI-EB and also believe that they may act in an electrochemical manner in regard to their corrosion protection effect on metal. Aromatic amine compounds that can be utilized in connection with our technology include various 1,4-benzenediamine and 4-aminodiphenylamine compounds, either alone or used in the form of mixtures. The following are particular examples of commercially available rubber antidegradants that can be selected for use: N,N'-di-sec-butyl-p-phenylenediamine; N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine; N,N'-diphenyl-p-phenylenediamine; 4-aminodiphenylamine; and N-isopropyl-N'-phenyl-p-phenylenediamine. A supplier of compounds of this type is Crompton Corporation.

             Another patent pending technology position, which should issue as a U.S. patent soon⁷ , involves the use of a rubber antioxidant that is employed in children's' balloons as a corrosion inhibiting material. It is N-phenyl-N'-(p-toluenesulfonyl)-p-phenylenediamine (available as ARANOX antioxidant from Crompton Corporation). The patent covers the use of this material either neat, in solvent, or in solvent in admixture with a polymeric binder.

             Interested parties desiring to test the embryonic approaches described herein, with a view to their future development and commercialization, under appropriate license, are invited to contact Polymer Alloys for further non-confidential information. Contact Information: Richard P. Fennelly; Director of Licensing and Business Development; Polymer Alloys LLC; E-Mail (preferred communication means): fenquarry@aol.com; Mailing Address: Box 286; Shrub Oak, New York 10588

1. PPE is, for example, available from General Electric Plastics (Pittsfield, MA), as their"PPO" brand resin. They are the dominant worldwide producer of this resin, with Asahi Chemicals, in Japan, and BASF, in Europe, being other suppliers. It is almost exclusively used as a resin for blending with other polymers, such as polystyrene, for the manufacture of engineering resins with attractive properties. GE Plastics, however, has recently introduced a low molecular weight oligomer of PPO ("PPO SA120") that they are targeting to the adhesives and coatings industries.
   
   
2. A full text copy of any U.S. patent listed in this article can be accessed and downloaded/printed by going to the website , doing a patent number search, and clicking on the displayed hypertext link to obtain the patent.
   
   
3. U.S. Patent No. 3,907,613 to J. Bures and collaborators.
   
   
4. Polyaniline is an electroactive polymer that Panipol Oy and DuPont/Ormecon market for a variety of uses, including the corrosion protection of metal.
   
   
5. One school of thought believes that the undoped form may be more soluble in the selected solvent and that the lack of migratory, acidic dopants might be more conducive to the long term corrosion protection effect conferred by the polyaniline material. Related work by IBM research personnel indicated superior corrosion protection effect for the undoped form of polyaniline on silver and copper (see Journal of the Electrochemical Society, Vol. 144, No. 2, Feb. 1997, pp. 436-442. Dr. Gordon Wallace (Univ. of Wollongong - Australia) has authored an abstract of an interesting paper (POLY #49) that was given at the American Chemical Society National Meeting in Washington, D.C. in August, 2000. The abstract reports a de-doping/re-doping study of organic soluble PANI on carbon steel and concludes that the non-doped EB form exhibits better corrosion protection than any of the doped versions that were tested. Also see, B.C. Beard et al. "XPS Evidence of Redox Chemistry between Cold Rolled Steel and Polyaniline", Chem. Mater. 1997, 9, 1949-1953.
   
   
6. U.S. Patent No. 5,853,462 (obtained through assignment from a prior owner).
   
   
7. At the time of the final preparation of this paper (late August, 2000), the issuance date of the patent is expected in September-October, 2000.