There is disclosed a plasma electrolytic oxidation process for generating a ceramic coating on a surface of a workpiece made of an alloy comprising a base metal and one or more secondary metals. A series of electrical current pulses are applied to the metallic workpiece in an electrolyte so as to generate plasma discharges at the surface of the metallic workpiece to form the ceramic coating. The electrolyte comprises at least one chelating agent selected to bind with ions of at least one of the one or more secondary metals that are released from the workpiece during the plasma electrolytic oxidation process. This helps to prevent or hinder a concentration of secondary metal compounds at an outer surface of the ceramic coating.
There is disclosed a method of forming a high luminosity inorganic coating on an aluminium or aluminium alloy article, wherein the article is immersed in an electrolyte and subjected to a plasma anodising process, wherein the coating has a luminosity L*≥ 80.0% and comprises at least 50wt% gamma alumina. Also disclosed are inorganic coatings formed by the method, and aluminium or aluminium alloys coated by the method.
There is disclosed an insulated metal substrate, consisting of a dielectric oxide coatings of high crystallinity (>vol90%) on aluminium, magnesium or titanium and high thermal conductivity (over 6Wm-1 K-1), formed by plasma electrolytic oxidation on a surface comprising aluminium, magnesium or titanium. There is also disclosed a plasma electrolytic oxidation process for generating dielectric oxide coatings of controlled crystallinity on a surface of a metallic workpiece, wherein at least a series of positive pulses of current are applied to the workpiece in an electrolyte so as to generate plasma discharges, wherein discharge currents are restricted to levels no more than 50mA, discharge durations are restricted to durations of no more than 100µs and are shorter than the durations of each the positive pulses, and/or by restricting the power of individual plasma discharges to under 15W. There is also disclosed an insulated metal substrate capable of withstanding exposure to high temperatures (over 300°C) and thermal shock or repeated thermal cycling of over 300°C, as a result of excellent adhesion of the insulating dielectric to the metal substrate, and the mechanically compliant nature of the coating (E ~20-30GPa). Furthermore, there is disclosed a method of making these insulated metal substrates so thin as to be mechanically flexible or pliable without detriment to their electrical insulation.
The present invention relates to a photocatalyst and a method of manufacturing a photocatalyst. More specifically, the present invention relates to a high surface area TiO 2 photocatalyst formed by electrolytic discharge oxidation (EDO) of a substrate comprising titanium. A flexible high surface area photocatalyst architecture comprising a compliant, cohesive, well-adhered and highly porous surface layer of the anatase phase of titanium dioxideis provided. The highly porous surface layer of the anatase phase of titanium dioxideisformed in a single step by the electrolytic oxidation of a titanium surface on a permeable, flexible, and electrically conductive substrate sponge structure.
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.
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