Process for the enhanced corrosion protection of valve metals
First Claim
1. A process comprising:
- a plasma electrolytic oxidation step on a surface of a valve metal that comprises surface asperities;
a chemical passivation step performed on the surface of the valve metal, wherein the combination of the plasma electrolytic oxidation step and the chemical passivation step forms an electrically insulating coating on the surface of the valve metal; and
contacting the electrically insulating coating under high pressure with an adjoining metal component, wherein the electrically insulating coating is sufficiently thin that the surface asperities of the valve metal surface project through the electrically insulating coating to allow galvanic electrical continuity from the surface asperities to the adjoining metal component, and wherein the coating includes an oxide layer impregnated with a chemical passivating agent configured to provide active corrosion protection of the valve metal in an event of physical breach of the oxide layer.
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Accused Products
Abstract
A process for the corrosion protection of metals such as magnesium, aluminium or titanium, where at least two steps are used, including both plasma electrolytic oxidation and chemical passivation. The combination of these two processing steps enhances the corrosion resistance performance of the surface beyond the capability of either of the steps in isolation, providing a more robust protection system. This process may be used as a corrosion protective coating in its own right, or as a protection-enhancing pre-treatment for top-coats such as powder coat or e-coat. When used without an additional top-coat, the treated parts can still retain electrical continuity with and adjoining metal parts. Advantages include reduced cost and higher productivity than traditional plasma-electrolytic oxidation systems, improved corrosion protection, greater coating robustness and electrical continuity.
14 Citations
11 Claims
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1. A process comprising:
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a plasma electrolytic oxidation step on a surface of a valve metal that comprises surface asperities; a chemical passivation step performed on the surface of the valve metal, wherein the combination of the plasma electrolytic oxidation step and the chemical passivation step forms an electrically insulating coating on the surface of the valve metal; and contacting the electrically insulating coating under high pressure with an adjoining metal component, wherein the electrically insulating coating is sufficiently thin that the surface asperities of the valve metal surface project through the electrically insulating coating to allow galvanic electrical continuity from the surface asperities to the adjoining metal component, and wherein the coating includes an oxide layer impregnated with a chemical passivating agent configured to provide active corrosion protection of the valve metal in an event of physical breach of the oxide layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification