Method of anodizing metallic surfaces and compositions therefore
AssigneesChemetall GmbH, Alonim Holding Agricultural Cooperative Society Ltd.
InventorIlya Ostrovsky
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AssigneesChemetall GmbH, Alonim Holding Agricultural Cooperative Society Ltd.
InventorIlya Ostrovsky
Estimating the term…
A method of treating metallic workpieces with an anodizing solution, compositions of the anodizing solution and the coatings prepared with this anodizing solution for anodizing metallic surfaces, especially surfaces of magnesium, magnesium alloys, aluminum and aluminum alloys, are disclosed. The compositions are basic aqueous solutions comprising a water-soluble inorganic hydroxide, phosphorus and oxygen containing anions, at least one surfactant and an alkaline buffer based on at least one alkaline hydrolyzed silane, on at least one alcohol showing at least one alkaline radical group or on a mixture of them.
A method of treating the surface of a metallic workpiece comprising the steps of:
A method of treating the surface of a metallic workpiece comprising the steps of:
A method of treating the surface of a metallic workpiece comprising the steps of:
A method of treating the surface of a metallic workpiece comprising the steps of:
A method of treating the surface of a metallic workpiece comprising the steps of:
A method of treating the surface of a metallic workpiece having at least on a portion of the metallic surface an anodizable material whereby the method comprises the steps of:
A method of treating the surface of a metallic workpiece having at least on a portion of the metallic surface an anodizable material whereby the method comprises the steps of:
A method of treating the surface of a metallic workpiece having at least on a portion of the metallic surface an anodizable material whereby the method comprises the steps of:
Dependencies are inferred from the claim text.
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Anodisation: anodisation under pulsed or modulated current or potential
Anodisation: anodisation with spark discharge
Of aluminium or alloys based thereon: characterised by the electrolytes used
Anodisation: of magnesium or alloys based thereon
Term ended 18 Feb 2024 (estimated)
The present invention is directed to a composition of an anodizing solution which is useful for the treatment of surfaces of anodizable metallic materials like magnesium, magnesium alloys, aluminum and aluminum alloys, to a method of treating the surface of a metallic workpiece with an anodizing solution as well as to the coatings generated.
The light weight and strength of light metals and their alloys and especially of magnesium and magnesium alloys makes products fashioned therefore highly desirable for use in manufacturing critical components of, for example, aircrafts, terrestrial vehicles and electronic devices. One of the most significant disadvantages of magnesium and magnesium alloys is corrosion. Exposure to corrosive or oxidizing conditions causes magnesium and magnesium alloy surfaces to corrode rather quickly, corrosion that is both unaesthetic and reduces strength.
There are many methods for improving the corrosion resistance of a magnesium and magnesium alloy workpiece by modifying the surface of the workpiece. It is generally accepted that the best corrosion resistance for magnesium and magnesium alloy surfaces is achieved by anodizing. In anodizing, a metallic workpiece is used as an anode of an electrical circuit. The circuit includes an electrolyte bath in which the workpiece is contacted, mostly by immersing, seldom by spraying. Depending on the properties of the current used, the bath temperature and the composition of the electrolyte bath, the surface of the workpiece is modified in various ways.
FIG. 1 shows the current changes using the controlled micro-sparking regime.
FIG. 2 shows the current changes with inadequate chemical conditions or anodizing conditions.
FIG. 3 shows possible current developments with excessive anodizing conditions. FIG. 3-a demonstrates a process where a stead burning of bigger local flames or a regional flame over the metallic surface occurs. FIG. 3-b demonstrates a process where a big local break-down of the coating occurs first, followed by many small break-downs.
According to the teachings of the present invention there is provided an aqueous composition, especially an aqueous solution, useful for the anodizing especially of magnesium or a magnesium alloy surface the composition. The aqueous composition may be a solution or dispersion, often being a solution. This anodizing composition contains preferably phosphorus and oxygen containing anions, at least one surfactant, at least one water-soluble inorganic hydroxide and at least one constituent selected from the group consisting of alcohols comprising at least one alkaline radical group, of at least one hydrolyzed alkaline silane and a mixture of them in water having a pH greater than 7. It is especially favorable that the phosphorus and oxygen containing anions contain phosphate anions, e.g. orthophosphate anions. Preferably, the at least one alcohol contains at least one alcohol having at least one amino group.
According to a feature of the present invention, the phosphorus and oxygen containing anions are preferably selected from the group consisting of mono-, di-, tri-P atoms containing groups like in an orthophosphate, hydrophosphate or pyrophosphate and of a six P atoms containing group like in a hexametaphosphate.
According to a feature of the invention, the phosphate anions are preferably provided from at least one compound selected from the group consisting of KH2PO4, K2HPO4, NaH2PO4 and Na2HPO4, preferably added as water-soluble phosphate salt, especially in the range from 0.001 to 6.0 M.