ANTI-AGING PERIODIC VARIABLE REACTION BLACK CHROMIUM COATING FILM AND FORMING METHOD THEREOF

Abstract

The disclosure provides an anti-aging periodic variable reaction black chromium coating film, sequentially comprising: an aluminum alloy matrix, a silane conversion film, a high-gloss organic resin coating, a metal compound and metal element periodic variable content alloy coating film, and a transparent resin coating. The disclosure simultaneously provides a method for forming the anti-aging periodic variable reaction black chromium coating film.

Claims

1. An anti-aging periodic variable reaction black chromium coating film, sequentially comprising: an aluminum alloy matrix, a silane conversion film, a high-gloss organic resin coating, a metal compound and metal element periodic variable content alloy coating film and a transparent resin coating; wherein the silane conversion film is obtained using a silane pretreatment passivation process, the high-gloss organic resin coating film is made of an epoxy resin powder coating, the metal compound and metal element periodic variable content alloy coating film contains 0-90% of nickel, 10%-100% of chromium, 0-90% of chromium carbide and 0-90% of nickel carbide, the transparent resin coating is a pure acrylic resin coating having a thickness of 80-150 m, and the high-gloss organic resin coating has a thickness of 120-250 m.

2. A method for forming an anti-aging periodic variable reaction black chromium coating film, comprising a process flow of: silane pretreatment, spraying of high-gloss medium powder, coating, and spraying of transparent powder (1) the silane pretreatment on a surface of an aluminum alloy or other metal comprises steps of hot water washing, de-greasing and alkaline washing, hot water washing, water washing, acid washing, pure water washing, pure water washing, silane passivation, pure water washing, sealing, pure water washing, and moisture drying; (2) the spraying of a high-gloss powder coating in the process flow refers to electro-statically spraying an epoxy powder coating or polyester powder coating onto a metal surface of a hub and curing same; (3) the coating refers to high-vacuum magnetron sputtering on the surface of the hub after curing the medium powder, sputtering targets include a pure chromium target and a nickel-chromium metal target, the two targets are set with different power according to colors and opened for coating according to the process sequence, the hub can auto-rotate and revolve in an equipment, premixed gas of argon and acetylene is introduced during coating to form a chromium and chromium carbide coating film primer having a thickness of 5-10 nm, the formed coating film has good adhesion to the high-gloss organic coating, then the nickel-chromium alloy target is opened, the double targets work together to form a chromium, nickel, nickel-chromium alloy, chromium carbide and nickel carbide deposited film having a thickness of 80-150 nm, finally, only the chromium target is opened to form a chromium and chromium carbide coating film having a thickness of 5-10 nm, and an entire reaction coating film thickness is 120-250 nm; the surface of the hub is sputtered in a certain order and proportion; (4) the spraying of transparent powder in the process flow refers to spraying transparent powder onto the surface of the coated hub and curing same, the transparent powder is an acrylic resin or polyester powder coating.

3. The method for forming the anti-aging periodic variable reaction black chromium coating film according to claim 2, wherein in step (1) of pretreatment on the surface, the passivation is for a silane conversion film, a baking temperature of a moisture oven is 150 C., and a baking time is 30 min.

4. The method for forming the anti-aging periodic variable reaction black chromium coating film according to claim 2, wherein in step (2), the high-gloss medium powder is sprayed with a thickness of 80 to 150 m, a spoke surface curing temperature is 220 C., a curing time is 20 min, epoxy resin is preferred, and a hardness of the cured coating is 2-3 H; and after curing, the coated surface reaches a mirror finish, and a glass transition temperature of the coating is 80-120 C.

5. The method for forming the anti-aging periodic variable reaction black chromium coating film according to claim 2, wherein in step (3), a temperature of the coated workpiece is 80-150 C., a flow rate of the working gas argon is 40-80 cc/min, a coating current for the chromium target and the nickel-chromium alloy target is 15-30 A, and a voltage is more than or equal to 550 v and less than 800 v; a vacuum degree is (2-8)10.sup.3 Pa, a double target coating time is 15-40 s, the working gas is 99.999% argon, and the reaction gas is acetylene having the purity of 99.999%; a coating environment humidity is less than or equal to 50%; in the coating sequence, the premixed gas of argon and acetylene is introduced first, then a pure chromium power supply is turned on for coating 3-7 seconds, the double targets are simultaneously opened for 14-24 seconds, finally a pure chromium is separately coated for 3-7 seconds, the hub rotates while being sputtered, a periodic variable alloy black chromium coating film is formed, and the targets are cooled at a temperature of 15-20 C.

6. The method for forming the anti-aging periodic variable reaction black chromium coating film according to claim 2, wherein in step (3), argon and acetylene are premixed in advance, a percentage of the acetylene in the mixed gas is from 0 to 90%, and a total gas flow is 120-400 cc/min; and a brightness color L value is between 55 and 85.

7. The method for forming the anti-aging periodic variable reaction black chromium coating film according to claim 2, wherein in step (4), the pure acrylic transparent powder is sprayed with a thickness of 80-150 m, a surface curing temperature of the hub is 177 C., a curing time is 20 min, and a hardness of the coating is H level.

Description

DETAILED DESCRIPTION

[0026] Two kinds of targets are used in the embodiments of the coating method of the disclosure, one is a pure chromium target containing 99.95% of chromium by mass, and the other one is a nickel-chromium alloy having the purity of 99.95% and containing 18% of nickel. The working gas is argon having the purity of 99.999%; the reaction gas is acetylene having the purity of 99.999%; the equipment is a high-vacuum magnetron sputtering coating machine, and can be used for a reactive sputtering coating process. The aluminum wheel material is A356.2 aluminum alloy; the pretreatment adopts silane passivation treatment; the high-gloss medium coating is made of an epoxy powder coating; and the transparent coating is made of a pure acrylic transparent powder coating.

[0027] The coating is inspected in accordance with the US general motor hub coating performance standards, and the inspection items include Adhesion Cross-Cut Test, CASS, FLIFORM, high humidity resistance test, coating ultraviolet aging resistance, etc.

[0028] A method for forming an anti-aging periodic variable reaction black chromium coating film includes the process flow of: silane pretreatment, spraying of high-gloss medium powder, coating, and spraying of transparent powder.

[0029] (1) The silane pretreatment includes the steps of hot water washing, de-greasing and alkaline washing, hot water washing, water washing, acid washing, pure water washing, pure water washing, silane passivation, pure water washing, sealing, pure water washing, and moisture drying.

[0030] (2) The spraying of a high-gloss powder refers to electro-statically spraying an epoxy powder coating onto the metal surface of a hub and curing same, in which the base powder is epoxy resin powder or a polyester powder coating. After the coating is cured, the surface achieves mirror finish and has good adhesion to the aluminum matrix. The spraying thickness is 150 m.

[0031] (3) High-vacuum magnetron sputtering is performed on the surface of the hub after curing the medium powder, the sputtering targets include a pure chromium target and a nickel-chromium metal target, the sprayed high-gloss medium powder is completely cured, the temperature of the hub is 100 C., argon is introduced with the flow rate of 80 cc/min, the flow rate of acetylene is 240 cc/min, and the coating current is 15 A for the pure chromium target and 18 A for the nickel-chromium alloy target; the vacuum degree is 510.sup.3 Pa, the mixed gas is introduced, the pure chromium alloy is opened at the first stage, the coating time is 6 s, and the auto-rotation and revolution time is 3 s/rev; the pure chromium target and the nickel-chromium alloy target are opened at the second stage, the coating time is 30 s, and the auto-rotation and revolution time is 3 s/rev; and the pure Cr target is opened at the third stage, the coating time is 6 s, and the auto-rotation and revolution time is 3 s/rev. The nickel-chromium alloy used is an alloy material having the nickel content of 80%.

[0032] (4) The spraying of transparent powder refers to spraying transparent powder onto the surface of the hub after the PVD coating and curing same, the transparent powder is an acrylic resin powder coating, the transparent coating has good binding force with the coating film, and the resin itself also has aging resistance and other properties.

Comparative Example 1

[0033] A PVD protective layer is prepared using a common method in the art. The target is a single pure Cr target, the base powder is black, and the PVD semi-permeable film reaches a black chromium coating film. The adopted process method and coating structure are the same as those of the preparation method of the disclosure.

Comparative Example 2

[0034] A PVD protective layer is prepared using a common method in the art. The target is a single NiCr alloy target, the base powder is black, and the PVD semi-permeable film reaches a black chromium coating film. The adopted process method and coating structure are the same as those of the preparation method of the disclosure.

[0035] The following tests and comparisons are carried out using the multi-layer sputtered coatings with metal surface ductility in example 1 and comparative examples 1 and 2, as shown in the following table:

TABLE-US-00001 Comparative Comparative Group Example 1 Example 1 Example 2 Coating color L = 65.0, a = 0.1, L = 64.5, a = 0.1, L = 65.2, a = 0.1, b = 2.2 b = 2.2 b = 2.2 Surface No cracks Cracked No cracks cracking Coating film 130 nm 56 nm 58 nm thickness Adhesion 100% 100% 100% Cross-Cut Test shedding-free shedding-free shedding-free CASS 1.0 mm 1.6 mm 3.8 mm FLIFORM 2.3 mm 3.1 mm 5.8 mm Water No change, No change, No change, resistance test adhesion 100% adhesion 91% adhesion shedding-free shedding-free 77% shedding- free Anti-aging No change, No change, No change, adhesion 100% adhesion 65% adhesion coating film coating film 61% coating film shedding-free shedding-free shedding-free

[0036] It can be seen that in the method of the disclosure, the coating temperature, the argon flow rate, the acetylene flow rate, the coating current, the vacuum degree, the NiCr alloy target and the pure Cr coating time are the key parameters, and the mixing proportion of acetylene and argon and the coating parameters are the key of obtaining the coating film color, thickness and aging resistance. A coating film with good properties is obtained by the above process. In the disclosure, the technical solution of the example obtains the optimal condition by exploring the above conditions. Coating test results are best under this optimal condition.