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US 2003/0116442 A1Published application
Method for applying a metal layer to a light metal surface
AssigneeAtotech Deutschland GmbH
InventorsHeinrich Meyer, Mathias Wunsche
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AssigneeAtotech Deutschland GmbH
InventorsHeinrich Meyer, Mathias Wunsche
Estimating the term…
A process for applying a metal layer to surfaces of light metals is proposed, in which iron is electrolytically deposited on the surfaces from a deposition bath containing Fe(II) compounds using dimensionally stable anodes insoluble in the deposition bath. The process is especially suitable for coating cylinder faces of internal combustion engines and of rotationally symmetrical parts with layers having very high wear resistance, especially of valves, nozzles and other parts of high-pressure injection systems for motor vehicle engines. In addition, the present invention pertains to nanocrystalline iron-phosphorus layers, which can be formed preferably by depositing iron in the presence of compounds containing orthophosphite and/or hypophosphite. These layers also have good corrosion resistance besides the good wear resistance.
Process for applying a metal layer to surfaces of light metals, in which iron is deposited electrolytically from an aqueous deposition bath containing Fe(II) compounds on the surfaces using dimensionally stable anodes insoluble in the deposition bath, characterized in that the Fe(II) compounds are formed in a reaction of Fe(III) compounds formed during the oxidation of the Fe(II) compounds at the anodes with iron parts and that the current density on the anode surface is increased at least temporarily to the extent that the anodic current efficiency becomes exactly as high, at least in a time-averaged manner, for the oxidation of the Fe(II) compounds into the Fe(III) compounds as the cathodic current efficiency for the deposition of iron from the deposition bath.
Process in accordance with one of the above claims, characterized in that a diaphragm surrounding the anode is provided.
Process in accordance with one of the above claims, characterized in that the deposition bath additionally contains at least one compound selected from the group comprising hypophosphite, orthophosphite, molybdenum and tungsten compounds.
Process in accordance with one of the above claims, characterized in that surfaces of light metals from the group comprising aluminum, magnesium and their alloys are coated.
Use of the process in accordance with one of the above claims for coating cylinder faces of internal combustion engines and of rotationally symmetrical parts with layers having very high wear resistance, especially of valves, nozzles and other parts of high-pressure injection systems for motor vehicle engines.
Nanocrystalline iron-phosphorus layer.
Dependencies are inferred from the claim text.