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US 7,094,327 B2Granted
Compositions for the treatment of magnesium alloys
AssigneeUniveriste Pierre et Marie Curie
InventorsHélène Ardelean, Philippe Marcus
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AssigneeUniveriste Pierre et Marie Curie
InventorsHélène Ardelean, Philippe Marcus
Estimating the term…
The invention relates to a composition for treating magnesium alloys aimed at improving the resistance thereof to corrosion. The composition is an aqueous solution with a pH ranging between 7 and 10, containing a niobium salt, hydrofluoric acid, and optionally a zirconium salt, phosphoric acid, and boric acid. The alloy is treated in an electrochemical cell in which said alloy acts as an anode. The cell contains an inventive composition at a temperature between 20° C. and 40° C. as an electrolyte. An initial voltage which is sufficient to create a current density between 1.5 and 2.5 A/dm2 is applied to the cell, whereupon the voltage is progressively increased to a level ranging between 240 and 330 V in order to maintain the initial current density.
A composition for an anodizing treatment of a magnesium alloy, wherein the composition comprises an aqueous solution, containing a niobium salt and hydrofluoric acid, the pH of which solution is maintained at a value between 7 and 10, and wherein the niobium salt is an oxide or fluoride.
Dependencies are inferred from the claim text.
From the US filing history. Foreign family members aren’t listed.
Anodisation: of magnesium or alloys based thereon
Processes for the electrolytic or electrophoretic production of coatings
Term ended 31 Jan 2023 (estimated)
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1. Field of the Invention:
The present invention relates to the treatment of magnesium alloys with a view to improving their corrosion resistance.
2. Description of the Related Art:
A composition according to the invention for the anodizing treatment of a magnesium alloy is an aqueous solution containing a niobium salt, hydrofluoric acid, and optionally a zirconium salt, the pH of which solution is maintained at a value between 7 and 10, preferably between 8 and 9.5.
The niobium salt may be chosen from oxides and fluorides. Niobium pentoxide is particularly preferred.
It is preferable that the treatment composition be supersaturated with niobium pentoxide, corresponding to a concentration of 0.04 mol/l. Niobium pentoxide forms fluoroniobate (fluoroniobyl) complexes with hydrofluoric acid, these complexes decomposing water with evolution of hydrogen by being oxidized on the surface cathode sites. The magnesium ions formed on the anode sites react with the niobium complexes or complexes of other intermediate species to form, on the surface of the magnesium alloy, mixtures of hydrated niobium oxides (which are insoluble), of magnesium oxides, optionally of aluminum oxides and of other species.