Pulse-modulated DC electrochemical coating process and apparatus
AssigneeBASF Coatings GmbH
InventorsKlaus Arlt, Karin Eckert, Margaret Stockbrink, Rolf Schulte, Harald Berlin, Gerd Nienhaus
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Abstract
The present invention relates to a novel process for coating objects by means of direct current, in which process an adjustable DC voltage is pulse-modulated with an adjustable AC voltage. The process is useful for electrochemical coating of objects with resinous coating material. Preferably, the pulse modulation of the DC voltage is limited to certain time intervals during the coating process and the pulse modulation is connected and disconnected with an adjustable duty ratio.
Claims13
A method for electrochemical coating of objects with a resinous coating material comprising the steps of:
- applying a direct current to a bath of a cationic resinous coating material;
- pulse-modulating a DC voltage of said direct current by superimposing thereon an adjustable AC voltage component, wherein the pulse-modulation of the DC voltage is connected and disconnected with an adjustable duty ratio;
- and
- coating an object with the coating material while applying said direct current, wherein the resulting superimposed voltage does not change its direction and pulse-modulation of the DC voltage is limited to certain time intervals during the coating process.
A method for eletrochemical coating of objects with a resinous coating material comprising the steps of;
- applying a direct current to a bath of resinous coating material;
- pulse-modulating a DC voltage of said direct current by superimposing thereon an adjustable AC voltage component;
- and
- coating an object with the coating material while applying said direct current, wherein the resulting superimposed voltage does not change its direction and pulse-modulation of the DC voltage is limited to certain time intervals during the coating process, wherein the pulse modulation of the DC voltage is connected and disconnected with an adjustable duty ratio between 10:1 and 1:10, a connection duration being between 10 ms and 100 s.
An apparatus for coating objects using a pulse-modulated DC current signal comprising:
- a bath of an electro-dipping resinous coating material;
- a DC generator for producing a DC current signal that is applied to the electro-dipping bath of resinous coating material;
- an AC generator for producing an AC signal;
- and
- an automatic control circuit for selectively superimposing said AC signal onto said DC signal during limited time intervals of the coating process in which the AC generator is connected to and disconnected from the DC generator with an adjustable duty ratio.
Dependencies are inferred from the claim text.