Coating structure for chromate-free passivation of surface of aluminum alloy profile

Abstract

The utility model relates to the technical field of metal manufacturing, provides a chromium-free passivation coating structure on the surface of an aluminum alloy profile, and solves the problems of low adhesiveness, relatively poor weather resistance and poor appearance bright effect of the coating structure on the surface of the existing aluminum profile. Which comprises a coating structure body and is characterized in that the coating structure body comprises a base material layer on the innermost layer, a first pretreatment layer on the secondary inner layer, a second pretreatment layer on the middle layer, a chromium-free passivation layer on the secondary outer layer and a sealing layer on the outermost layer; and the thickness of the sealing layer is 10-70 microns.

Description

Technical Field

[0001] This utility model relates to the field of metal manufacturing technology, and in particular to a chromium-free passivation coating structure for the surface of aluminum alloy profiles. Background Technology

[0002] With increasing environmental awareness and ever-increasing demands on material performance in industrial production, chromium-free passivation technology for aluminum alloy profiles has gradually become a focus of industry attention. While traditional chromate passivation processes can effectively improve the corrosion resistance of aluminum alloys, their environmental impact and potential health risks cannot be ignored.

[0003] Chinese Patent Application No. 202020411233.1 discloses an environmentally friendly gold plating structure for die-cast aluminum alloy parts, comprising an aluminum alloy substrate and, sequentially from the inside out, a zinc immersion layer, an acidic zinc-nickel alloy plating layer, a chemical nickel plating layer, a pyrophosphate copper plating layer, an acidic copper plating layer, a bright nickel plating layer, a nickel-phosphorus alloy plating layer, and a gold plating layer. The gold plating structure disclosed in this utility model has an environmentally friendly preparation process. After 120 hours of neutral salt spray testing according to GB / T10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test", no corrosion products are generated on the surface of the plated part, demonstrating good corrosion resistance. However, the appearance and brightness of this aluminum alloy plating structure are relatively poor.

[0004] Chinese Patent Application No. 202223505551.2 discloses a highly corrosion-resistant composite coating for aluminum alloy substrates, comprising, from the inside out, a bottom Ni-P layer, an electroplated Cu layer, an intermediate Ni-P layer, and a Ni-P-PTFE layer. This novel highly corrosion-resistant composite coating improves the corrosion resistance of the coating and enhances the conductivity, wear resistance, and high-temperature resistance of the connector product shell (i.e., the aluminum alloy substrate), ensuring stable operation of the product under high-temperature conditions and in thunderstorms. However, the adhesion of this composite coating is low. Utility Model Content

[0005] Therefore, in view of the above problems, this utility model provides a chromium-free passivation coating structure for aluminum alloy profiles, which solves the problems of low adhesion, relatively poor weather resistance, and poor gloss effect of existing coating structures on aluminum profiles.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A chromium-free passivation coating structure for an aluminum alloy profile surface includes a coating structure body, which comprises an innermost substrate layer, a second innermost first pretreatment layer, a middle second pretreatment layer, a second outermost chromium-free passivation layer, and an outermost sealing layer; the thickness of the sealing layer is 10-70 micrometers.

[0008] Furthermore, both the first pretreatment layer and the second pretreatment layer are used to improve the adhesion of the coating structure body.

[0009] Furthermore, the substrate layer is an aluminum alloy profile.

[0010] Furthermore, the first pretreatment layer is an acidic degreasing agent layer.

[0011] Furthermore, the second pretreatment layer is an acidic etching layer.

[0012] Furthermore, the chromium-free passivation layer is a dense passivation film.

[0013] Furthermore, the sealing layer is an ultra-weather-resistant powder coating layer.

[0014] Furthermore, the sealing layer is used to improve the adhesion and weather resistance of the coating structure body.

[0015] By adopting the aforementioned technical solution, the beneficial effects of this utility model are as follows:

[0016] 1. First, an acidic degreasing agent layer is set on the surface of the substrate layer to destroy the structure of the grease, making it lose its stickiness, thereby removing it from the surface of the aluminum profile. The clean surface helps the bonding between the chromium-free passivation layer and the aluminum alloy profile.

[0017] 2. An acidic etching layer is set in the innermost layer of the coating structure to uniformly etch the surface of the aluminum alloy profile, forming a fine sand surface and increasing the surface roughness, so that the subsequent structural layers can better adhere to the aluminum alloy profile.

[0018] 3. A chromium-free passivation layer is set in the middle layer of the coating structure to form a dense passivation film, making the surface of the aluminum alloy profile smoother and more uniform, which helps to remove surface defects such as scratches generated during processing. Furthermore, the dense passivation film can improve the hardness and wear resistance of the metal surface, isolate the metal substrate from external corrosive media, and prevent further oxidation and corrosion.

[0019] 4. The outermost sealing layer of the coating structure is an ultra-weather-resistant powder coating layer, which has excellent weather resistance and corrosion resistance, and can resist the erosion of acid rain, ultraviolet rays, etc., thereby improving the durability and reliability of the product. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the coating structure in an embodiment of this utility model;

[0021] The labels in the diagram are as follows: 1-plating structure body, 2-substrate layer, 3-first pretreatment layer, 4-second pretreatment layer, 5-chromium-free passivation layer, 6-sealing layer. Detailed Implementation

[0022] The embodiment of this utility model is as follows:

[0023] refer to Figure 1 A chromium-free passivation coating structure for an aluminum alloy profile surface includes a coating structure body 1, which comprises an innermost substrate layer 2, a second innermost first pretreatment layer 3, a middle second pretreatment layer 4, a second outermost chromium-free passivation layer 5, and an outermost sealing layer 6. The sealing layer has a thickness of 60 micrometers. Both the first and second pretreatment layers are used to improve the adhesion of the coating structure body. The substrate layer is an aluminum alloy profile, the first pretreatment layer is an acidic degreasing agent layer, the second pretreatment layer is an acidic etching layer, the chromium-free passivation layer is a dense passivation film, and the sealing layer is an ultra-weather-resistant powder coating layer. The sealing layer is used to improve the weather resistance of the adhesion of the coating structure body.

[0024] Specifically, the acidic degreasing agent layer is formed by treating the aluminum alloy profile in a 1% ZHM1206 acidic degreasing agent solution for 1 minute at a temperature of 20°C. The acidic degreasing agent can effectively destroy the structure of the grease, making it lose its stickiness, thereby removing it from the surface of the aluminum profile. The clean surface helps the bonding between the chromium-free passivation layer and the aluminum alloy profile, thereby improving the adhesion and corrosion resistance of the coating.

[0025] The acid etching layer is formed by adding 1 part by weight of ammonium bifluoride to a 10% sulfuric acid solution, stirring and mixing evenly to obtain an acid etching mixture, and then immersing the degreased aluminum alloy profile in the acid etching mixture at a temperature of 20°C for 1 minute to perform acid etching treatment. The acid etching treatment can uniformly corrode the surface of the aluminum alloy profile, forming a fine sand-like surface, increasing the surface roughness, so that the subsequent structural layers can better adhere to the aluminum alloy profile.

[0026] The chromium-free passivation layer is prepared by adjusting the pH of the chromium-free treatment solution to 2.0. The chromium-free treatment solution is a 1% Chemetall 4500 mixed solution at 20°C. The aluminum alloy profile, after acid etching, is then immersed in the chromium-free treatment solution for 1 minute, followed by drying to form a dense passivation film. This results in a smoother and more uniform surface on the aluminum alloy profile, helping to remove surface defects such as scratches generated during processing. Furthermore, the dense passivation film improves the hardness and wear resistance of the metal surface, isolates the metal substrate from external corrosive media, and prevents further oxidation and corrosion.

[0027] The ultra-weather-resistant powder coating layer is applied by uniformly spraying the ultra-weather-resistant powder coating onto the surface of an aluminum alloy profile that has undergone chromium-free passivation treatment using an electrostatic spraying machine. The spray pressure of the electrostatic spraying machine is 0.4 MPa, and the coating thickness is controlled at 60 micrometers. The coating is then cured at 160°C for 15 minutes, removed, and cooled to form the sealing layer. The electrostatic spraying machine utilizes the principle of a high-voltage electrostatic field to charge the coating particles and uniformly adsorb them onto the surface of the aluminum alloy profile, forming a smooth and uniform coating. The ultra-weather-resistant powder coating has excellent weather resistance and corrosion resistance, resisting erosion such as acid rain and ultraviolet radiation, thus improving the durability and reliability of the product.

[0028] Although the present invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the present invention without departing from the spirit and scope of the present invention as defined in the appended claims, and all such changes shall be within the scope of protection of the present invention.

Claims

1. A chromium-free passivation coating structure for the surface of an aluminum alloy profile, comprising a coating structure body, characterized in that: The coating structure body includes an innermost substrate layer, a second innermost first pretreatment layer, a middle second pretreatment layer, a second outermost chromium-free passivation layer, and an outermost sealing layer; the thickness of the sealing layer is 10-70 micrometers.

2. The chromium-free passivation coating structure on the surface of an aluminum alloy profile according to claim 1, characterized in that: Both the first pretreatment layer and the second pretreatment layer are used to improve the adhesion of the coating structure body.

3. The chromium-free passivation coating structure on the surface of an aluminum alloy profile according to claim 1, characterized in that: The substrate layer is made of aluminum alloy profile.

4. The chromium-free passivation coating structure on the surface of an aluminum alloy profile according to claim 1, characterized in that: The first pretreatment layer is an acidic degreasing agent layer.

5. The chromium-free passivation coating structure on the surface of an aluminum alloy profile according to claim 1, characterized in that: The second pretreatment layer is an acid etching layer.

6. The chromium-free passivation coating structure on the surface of an aluminum alloy profile according to claim 1, characterized in that: The chromium-free passivation layer is a dense passivation film.

7. The chromium-free passivation coating structure on the surface of an aluminum alloy profile according to claim 1, characterized in that: The sealing layer is an ultra-weather-resistant powder coating layer.

8. The chromium-free passivation coating structure on the surface of an aluminum alloy profile according to claim 1, characterized in that: The sealing layer is used to improve the adhesion and weather resistance of the coating structure body.

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