Non-toxic corrosion-protection conversion coats based on rare earth elements
First Claim
1. A solid corrosion-inhibiting conversion coating formed on a substrate metal, the conversion coating comprising a rare earth element and an inorganic valence stabilizer combined to form a rare earth/valence stabilizer complex within the solid corrosion-inhibiting conversion coating, wherein the rare earth element is selected from cerium, praseodymium, terbium, or a combination thereof, and at least one rare earth element is in the tetravalent oxidation state in the rare earth/valence stabilizer complex in the solid corrosion-inhibiting conversion coating.
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Abstract
Conversion coatings comprising a rare earth element and a valence stabilizer combined to form a rare earth/valence stabilizer complex are described for substrate metals. The rare earth element is selected from cerium, praseodymium, terbium, or combinations thereof, and at least one rare earth element is in the tetravalent oxidation state. The coating bath may also contain a preparative or solubility control agent. The oxidized cerium, praseodymium or terbium is present in the coating in a “sparingly soluble” form. The valence stabilizers can be either inorganic or organic in nature. A number of cerium, praseodymium, or terbium/valence stabilizer combinations are presented that can equal the performance of conventional hexavalent chromium systems.
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Citations
44 Claims
- 1. A solid corrosion-inhibiting conversion coating formed on a substrate metal, the conversion coating comprising a rare earth element and an inorganic valence stabilizer combined to form a rare earth/valence stabilizer complex within the solid corrosion-inhibiting conversion coating, wherein the rare earth element is selected from cerium, praseodymium, terbium, or a combination thereof, and at least one rare earth element is in the tetravalent oxidation state in the rare earth/valence stabilizer complex in the solid corrosion-inhibiting conversion coating.
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26. A solid corrosion-inhibiting conversion coating formed on a substrate metal, the conversion coating comprising a rare earth element and an inorganic valence stabilizer combined to form a rare earth/valence stabilizer complex within the solid corrosion-inhibiting conversion coating, wherein
the rare earth element is selected from cerium, praseodymium, terbium, or a combination thereof, at least one rare earth element is in the tetravalent oxidation state in the rare earth/valence stabilizer complex in the solid corrosion-inhibiting conversion coating, and the rare earth/valence stabilizer complex is sparingly soluble in water at about 25° - C. and about 760 Torr.
- 27. A solid corrosion-inhibiting conversion coating formed on a substrate metal, the conversion coating comprising a rare earth element and a valence stabilizer combined to form a rare earth/valence stabilizer complex within the solid corrosion-inhibiting conversion coating, wherein the rare earth element is selected from cerium, praseodymium, terbium, or a combination thereof, and at least one rare earth element is in the tetravalent oxidation state, wherein the rare earth/valence stabilizer complex has a central cavity containing a cerium, praseodymium, or terbium ion and an additional ion, wherein the additional ion is B+3, Al+3, Si+4, P+5, Ti+4, V+5, V+4, Cr+6, Cr+3, Mn+4, Mn+3, Mn+2, Fe+3, Fe+2, Co+2, Co+3, Ni+2 , Ni+3, Ni+4, Cu+2, Cu+3, Zn+2, Ga+3, Ge+4, As+5, As+3, or Zr+4.
Specification