Method for Coating a Motor Vehicle Bodyshell Part, and Motor Vehicle Bodyshell Part

Abstract

A method for coating a motor vehicle part includes coating and subsequently painting. In the coating, a motor vehicle bodyshell part is coated with a metallic zinc coat as cathodic corrosion protection. In the subsequent painting, the coated motor vehicle bodyshell part is painted. The motor vehicle bodyshell part is chemically polished and/or electrochemically polished prior to the coating with the metallic zinc coat.

Claims

1.-7. (canceled)

8. A method for coating a motor vehicle part, comprising: coating a motor vehicle bodyshell part with a metallic zinc coat as cathodic corrosion protection; and subsequently painting the coated motor vehicle bodyshell part, wherein the motor vehicle bodyshell part is chemically polished and/or electrochemically polished prior to the coating with the metallic zinc coat.

9. The method according to claim 7, wherein the motor vehicle bodyshell part is generatively manufactured or cast and is subsequently chemically polished and/or electrochemically polished.

10. The method according to claim 8, wherein after the chemical polishing and/or the electrochemical polishing and prior to the coating with the zinc coat, the motor vehicle bodyshell part is cleaned by ultrasound.

11. The method according to claim 10, wherein the motor vehicle bodyshell part is a body component of the motor vehicle.

12. The method according to claim 11, further comprising: subjecting the motor vehicle bodyshell part to corundum blasting prior to the chemical polishing and/or the electrochemical polishing.

13. The method according to claim 12, wherein the motor vehicle bodyshell part is hot-dip galvanized.

14. An apparatus comprising: a motor vehicle bodyshell part having a base body which is coated with a zinc coat, and having a paint layer which is arranged on the zinc coat, wherein the base body is a chemically and/or electrochemically polished cast part and/or generatively manufactured component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 shows a method diagram for coating a motor vehicle bodyshell part, in which the motor vehicle bodyshell part is produced, chemically and/or electrochemically polished, coated with a metallic zinc coat and subsequently painted; and

[0016] FIG. 2 shows respective schematic views of a surface of the motor vehicle bodyshell part in different stages of a polishing operation or of a cleaning operation of the surface of the motor vehicle bodyshell part.

DETAILED DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 illustrates a method diagram for producing and coating a motor vehicle bodyshell part 5, wherein a particularly corrosion-resistant motor vehicle bodyshell part 5 is intended to be produced, which can be used in particular in a wet region of a motor vehicle.

[0018] In the method, in a first method step 1, the motor vehicle bodyshell part 5 is generatively manufactured or cast. This means that the motor vehicle bodyshell part 5 is either produced in a casting method or is constructed layerwise by additive manufacturing. In the present case, the motor vehicle bodyshell part 5 produced in the context of the first method step 1 is a body component. In a second method step 2, the motor vehicle bodyshell part 5 is pretreated. In the context of this pretreatment, the motor vehicle bodyshell part 5 is at least chemically and/or electrochemically polished. In addition, the motor vehicle bodyshell part 5 can be subjected to corundum blasting and/or ultrasonic cleaning. In a third method step 3, the motor vehicle bodyshell part 5 is then coated with a metallic zinc coat, in particular hot-dip galvanized. This metallic zinc coat serves as cathodic corrosion protection and thus functions as sacrificial anode for a particularly high corrosion resistance of the motor vehicle bodyshell part 5. In a fourth method step 4 subsequent to the galvanization, the motor vehicle bodyshell part 5 is painted, such that a paint is applied onto the motor vehicle bodyshell part 5, on the metallic zinc coat. In the present case, the motor vehicle bodyshell part 5 is cathodically dip-painted.

[0019] FIG. 2 illustrates a surface of the motor vehicle bodyshell part 5 in different states during the second method step 2 in the context of the pretreatment. The surface of the, in the present case, precision-cast motor vehicle bodyshell part 5 is shown in a plan view as a first state 6, after the casting operation and prior to a polishing operation. The surface of the motor vehicle bodyshell part 5 is shown both in a plan view and in a sectional view in a second state 7, after the surface of the motor vehicle bodyshell part 5 has been subjected to a corundum blasting operation. The surface of the motor vehicle bodyshell part 5 is furthermore illustrated in a third state 8 both in a plan view and in a sectional view, wherein the surface of the motor vehicle bodyshell part 5 in the third state 8 has been subjected to corundum blasting and then chemically polished. Moreover, the surface of the motor vehicle bodyshell part 5 is illustrated in a plan view and in a sectional view in a fourth state 9, in which the surface of the motor vehicle bodyshell part 5 has been subjected to corundum blasting, chemically polished, and also subjected to ultrasonic cleaning. Moreover, the surface of the motor vehicle bodyshell part 5 is illustrated in a plan view in the fifth state 10 thereof, wherein the surface of the motor vehicle bodyshell part 5 in the fifth state 10 has been subjected to corundum blasting twice, and thus chemically polished twice, and also subjected to ultrasonic cleaning.

[0020] In the second method step 2, the surface of the motor vehicle bodyshell part 5 passes first through the first state 6, then the second state 7, then the third state 8, then the fourth state 9 and subsequently the fifth state 10. In the present case, after reaching the fifth state 10, the surface of the motor vehicle bodyshell part 5 is provided with the zinc coat in the third method step 3. As can be seen in FIG. 2, contaminants and also surface roughnesses of the surface of the motor vehicle bodyshell part 5 decrease continuously from the first state 6 through to the fifth state 10. Consequently, by means of the pretreatment of the motor vehicle bodyshell part 5 and in particular the chemical and/or electrochemical polishing, it is possible to achieve a surface refinement of the surface of the motor vehicle bodyshell part 5, in particular a particularly clean and also particularly smooth surface of the motor vehicle bodyshell part 5.

[0021] Currently, no chemical surface finishing or surface cleaning of components composed of steel or iron, which have been produced by casting or additive manufacturing, has been established. A respective surface of these components is currently not provided with a closed paint layer and/or a closed zinc coat. Consequently, components produced in the context of additive manufacturing or cast manufacturing are currently not used in regions of a motor vehicle body which are subject to corrosion. Contaminants of the surface of these components can lead, after the respective surfaces have been galvanized and painted, to bubbles in the paint, which are undesired.

[0022] In order to overcome these disadvantages, the surface of the motor vehicle bodyshell part 5, which has been generatively manufactured or cast, is cleaned and/or leveled by a chemical aftertreatment, in particular chemical polishing and/or electrochemical polishing and/or electrochemical pulse polishing, in such a way that a sealed zinc layer and/or a sealed cathodic paint layer can be deposited on the surface thereof. The sealing of the paint layer and/or of the zinc coat can be additionally improved by subjecting the surface of the motor vehicle bodyshell part 5 to ultrasonic cleaning after the chemical and/or electrochemical polishing operation.

[0023] The described method makes it possible for the generatively manufactured or cast motor vehicle bodyshell part 5 to be able to be used in a motor vehicle body and in particular in a wet region of the motor vehicle without additional measures such as a coating with polyvinyl chloride. By means of the method, the generatively manufactured or cast motor vehicle bodyshell part 5 can be provided with the particularly advantageous corrosion properties described.

LIST OF REFERENCE DESIGNATIONS

[0024] 1 First method step [0025] 2 Second method step [0026] 3 Third method step [0027] 4 Fourth method step [0028] 5 Motor vehicle bodyshell part [0029] 6 First state [0030] 7 Second state [0031] 8 Third state [0032] 9 Fourth state [0033] 10 Fifth state