Lynntech Coatings, Ltd.

Lynntech, Inc.

Cahit Eylem

Zoran Minevski

Carl Nelson

Jason Maxey

Eric T Clarke

A method employing oxide film conversion coatings prepared using ferrate (VI) as the oxidizing agent is disclosed. Metal substrates or surfaces, such as aluminum, aluminum alloys or other metals, are contacted with an aqueous solution comprising ferrate (VI) anions to form a corrosion resistant conversion coating on the surface thereof. The ferrate anion concentration is preferably between about 0.0166% and about 1.66% by weight. The coating process is carried out by dipping, spraying, or painting at temperatures ranging from 25&#xb0; C. to 100&#xb0; C. for a period of time ranging from about 1 second to about 5 minutes.

Ferrate conversion coatings for metal substrates

The present invention provides a conversion coating solution containing polymetalates and/or heteropolymetalates to oxidize the surface of various metal substrates. The polymetalates have the general formula MO, where M is selected from the group comprising Mo, V and W. The heteropolymetalates have the general formula BMO, where B is a heteroatom selected from P, Si, Ce, Mn or Co, and M is again selected from Mo, V, W or combinations thereof. The concentration of polymetalates and/or heteropolymetalates anions is preferably between about 1% and about 5% by weight. Examples of typical anions used include, but are not limited to, (PMoO), (PMoVO), (MnPWO), (PWO), (SiMoO), (SiWO), (MoO), (CeMoO)and mixtures thereof.

Polymetalate and heteropolymetalate conversion coatings for metal substrates

The present invention provides a conversion coating solution containing polymetalates and/or heteropolymetalates to oxidize the surface of various metal substrates. The polymetalates have the general formula M O , where M is selected from the group comprising Mo, V and W. The heteropolymetalates have the general formula BM O , where B is a heteroatom selected from P, Si, Ce, Mn or Co, and M is again selected from Mo, V, W or combinations thereof. The concentration of polymetalates and/or heteropolymetalates anions is preferably between about 1% and about 5% by weight. Examples of typical anions used include, but are not limited to, (PMo O ) , (PMo V O ) , (MnPW O ) , (PW O ) , (SiMo O ) , (SiW O ) , (Mo O ) , (CeMo O ) and mixtures thereof.

A method employing oxide film conversion coatings prepared using ferrate (VI) as the oxidizing agent is disclosed. Metal substrates or surfaces, such as aluminum, aluminum alloys or other metals, are contacted with an aqueous solution comprising ferrate (VI) anions to form a corrosion resistant conversion coating on the surface thereof. The ferrate anion concentration is preferably between about 0.0166% and about 1.66% by weight. The coating process is carried out by dipping, spraying, or painting at temperatures ranging from 25&deg; C. to 100&deg; C. for a period of time ranging from about 1 second to about 5 minutes.

A conversion coating solution and process forms a stable and corrosion-resistant layer on metal substrates or layers or, more preferably, on a boehmite layer or other base conversion coating. The conversion coating process involves contacting the substrate, layer or coating with an aqueous alkali metal isomolybdate solution in order to convert the surface of the substrate, layer or coating to a stable conversion coating. The aqueous alkali metal molybdates are selected from sodium molybdate (Na MoO ), lithium molybdate (Li MoO ), potassium molybdate (K MoO ), or combinations thereof, with the most preferred alkali metal molybdate being sodium molybdate. The concentration of alkali metal molybdates in the solution is preferably less than 5% by weight. In addition to the alkali metal molybdates, the conversion coating solution may include alkaline metal passivators selected from lithium nitrate (LiNO ), sodium nitrate (NaNO ), ammonia nitrate (NH NO ), and combinations thereof; lithium chloride, potassium hexafluorozirconate (K ZrF ) or potassium hexafluorotitanate (K TiF ).

Isomolybdate conversion coatings

A conversion coating process that forms a stable and corrosion-resistant oxide layer on metal or metal oxide substrates or layers. Particularly, the conversion coating process involves contacting the metal or metal oxide substrate or layer with the aqueous calcium hydroxide solutions in order to convert the surface of the substrate to a stable metal oxide layer or coating. According to the present invention, the calcium hydroxide solution is prepared by removing carbon dioxide from water or an aqueous solution before introducing the calcium hydroxide. In this manner, formation of calcium carbonate particles is avoided and the porosity of the conversion coating produced by the calcium hydroxide solution is reduced to below about 1%.

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College Station, TX, United States of America

Cahit Eylem