A method of treating a metal surface

Abstract

The present application relates to a kind of metal surface treatment method, by forming metal surface treatment agent film layer on the metal substrate surface of laminated film, especially using two film layers of same composition and different mass ratio of trivalent chromium in metal surface treatment agent and compound B, when laminating, the layer film of first metal surface treatment agent appears fracture and other phenomena due to metal extension, the layer film formed by second metal surface treatment agent fills in the fracture, and because the composition of two layer films is same, the binding force with metal is little different, the binding of the layer film of second metal surface treatment agent with metal substrate is actually greater than the layer film of first metal surface treatment agent, when the layer film of second metal surface treatment agent is combined with metal substrate through fracture, the stress at the crack is balanced at the same time, and the binding force of the layer film of second metal surface treatment agent with laminated film is higher than the binding force of the layer film of first metal surface treatment agent with laminated film, avoid the problem of blistering of laminated film or resin film.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal corrosion prevention, in particular to a metal surface treatment method. BACKGROUND

[0002] Laminating processing is a processing method of heating and pressing a resin film on the surface of a metal material, and is one of the metal material surface coating methods for preventing corrosion of the metal material surface, and has been widely used in various fields. Compared with a method of forming a resin protective film by applying a resin composition on the surface of a metal material and drying it, laminating processing produces less solvent during drying and also produces less waste gas, and its use has gradually expanded from the environmental protection aspect, and it has now been used for aluminum sheet materials, steel sheet materials, aluminum foil or stainless steel foil for packaging, and the like.

[0003] In particular, in recent years, electronic products, outer packaging materials for lithium ion batteries, and the like use metal foils such as aluminum foil or stainless steel foil that are light in quality and high in barrier properties. For the laminated film used in the above laminating processing, after being attached to the metal material, heating and pressing are performed, and compared with a general resin coating film formed by applying a resin composition and drying it, it has advantages such as being able to suppress waste of raw materials, having fewer pinholes, and having excellent processing properties.

[0004] When laminating a laminated film on the surface of a metal material, in order to improve the adhesion of the laminated film to the metal surface and the corrosion resistance of the metal surface, after degreasing the metal surface, a chemical conversion treatment such as a chromic phosphate is usually performed, resulting in a treatment liquid containing hexavalent chromium that is harmful to the environment.

[0005] Therefore, CN 102741453 A proposes a metal surface treatment agent and a metal surface treatment method, in which a metal surface treatment agent film is formed on the surface of a substrate made of stainless steel to form a laminated film or a resin coating film, and the metal surface treatment agent contains a trivalent chromium compound A and at least one compound selected from organic compounds and inorganic compounds having film-forming properties, and the mass ratio of the trivalent chromium compound A to the compound B is 0.005-1, and the method of use is to apply the above metal surface treatment agent to the surface of a substrate made of stainless steel, and then heat and dry it at a temperature of 60-250 degrees to form a surface treatment film. According to this technical solution, a surface treatment film with high adhesion that is not prone to peeling or cracking on the surface treatment film can be formed, and further, the adhesion can be maintained stably for a long time when exposed to solvents and acids.

[0006] The metal surface treatment agent improves the anti-peeling performance and corrosion resistance between the stainless steel substrate and the laminated film or resin coating film, but there are still some deficiencies in the use process. The treatment technology has good effect when used in the substrate of stainless steel, but when used in other metal materials such as aluminum substrate or zinc substrate, because of the difference in ductility during lamination and the combination of trivalent chromium in the metal surface treatment agent and the metal surface, the surface treatment film will have crack phenomenon. Usually these cracks are supplemented by the laminated film or resin coating film during the lamination process, but this also causes the change of the bonding force between the laminated film or resin coating film and the metal surface treatment agent, resulting in the blister phenomenon. SUMMARY

[0007] The purpose of the present application is to provide a metal surface treatment method to solve the problem of blister phenomenon of the laminated film or resin coating film of the metal surface treatment of the prior art.

[0008] The present application is realized by the following technical solutions:

[0009] A metal surface treatment method, comprising the following steps:

[0010] S1, cleaning the surface of the metal substrate;

[0011] S2, after the cleaned metal substrate is coated with a first metal surface treatment agent, it is naturally dried at room temperature for 0.5-1 hours;

[0012] S3, a second metal surface treatment agent is coated on the first metal surface treatment agent after natural drying, and then heated and dried at a temperature of 80-220°C to form a surface treatment film;

[0013] The first metal surface treatment agent and the second metal surface treatment agent have the same composition, and the difference is the content of trivalent chromium.

[0014] Preferably, the first metal surface treatment agent is composed of a compound A containing trivalent chromium and a compound B, wherein the compound B is a film-forming vinyl resin;

[0015] The mass ratio of metallic chromium in the compound A containing trivalent chromium to the vinyl resin is 0.2-0.25;

[0016] The second metal surface treatment agent is composed of a compound A containing trivalent chromium and a compound B, wherein the compound B is a film-forming vinyl resin; the mass ratio of metallic chromium in the trivalent chromium compound A to the vinyl resin is 0.35-0.8.

[0017] Preferably, the second metal surface treatment agent is composed of compound A and compound B containing trivalent chromium, wherein the mass ratio of metallic chromium in trivalent chromium compound A to vinyl resin is 0.5-0.8.

[0018] Preferably, the metal matrix is ​​made of stainless steel, aluminum, or aluminum alloy.

[0019] Preferably, the thickness of the first metal surface treatment agent film on the metal substrate surface is greater than the thickness of the second metal surface treatment agent film.

[0020] Preferably, the ratio of the thickness of the first metal surface treatment agent film to the thickness of the second metal surface treatment agent film is 1.2-1.5:1.

[0021] The beneficial effects of this invention are:

[0022] This technical solution's metal surface treatment method involves forming a metal surface treatment agent film on the surface of a laminated metal substrate. Specifically, it uses two films with the same composition but different mass ratios of trivalent chromium and compound B in the metal surface treatment agent. Whether for stainless steel substrates or aluminum or aluminum alloys with better ductility during lamination, when the first metal surface treatment agent film breaks due to metal ductility during lamination, the second metal surface treatment agent film fills the breakage due to the difference in ductility. Because the two films have the same composition, their bonding strength with the metal is not significantly different. However, the actual bonding strength between the second metal surface treatment agent film and the metal substrate is greater than that between the first and second metal surface treatment agent films. When the second metal surface treatment agent film bonds to the metal substrate through the breakage, it simultaneously balances the stress at the crack. Furthermore, the bonding strength between the second metal surface treatment agent film and the laminated film is higher than that between the first and second metal surface treatment agent films, thus avoiding the problem of bubbling in the laminated film or resin film. Detailed Implementation

[0023] The technical solutions of the present invention will be described in detail below through embodiments. The following embodiments are merely exemplary and can only be used to explain the technical solutions of the present invention, and should not be construed as limiting the technical solutions of the present invention.

[0024] In the following embodiments of this application, the reagents and components involved are all commercially available, and there are no reagents or raw materials that need to be described separately. Similarly, the equipment used is also commonly used in the field and will not be described in detail here.

[0025] Example 1

[0026] A method for treating metal surfaces includes the following steps:

[0027] S1. Cleaning the aluminum substrate surface. This cleaning process is a standard procedure in metal surface treatment, and the cleaning agents used are also standard products. No special requirements are specified here. All cleaning agents that can be used to clean metal substrates are applicable. This step must include a water cleaning process. In addition, acid or alkali is not suitable for cleaning in this step because this technical solution is not suitable for causing micro-corrosion of the aluminum substrate surface through the use of acid or alkali. That is, the aluminum substrate surface treated by this technical solution is relatively smooth.

[0028] S2. After coating the cleaned aluminum substrate with the first metal surface treatment agent, allow it to air dry at room temperature for 1 hour. In this embodiment, the first metal surface treatment agent consists of compound A containing trivalent chromium and compound B, wherein compound B is a film-forming vinyl resin; the mass ratio of metallic chromium in compound A to the vinyl resin is 0.2. In this embodiment, the exact structure of the vinyl resin is not required, as the focus of this technical solution is on the treatment method.

[0029] S3. Apply the second metal surface treatment agent to the first metal surface treatment agent after it has dried naturally, and then heat and dry it at 160°C to form a surface treatment film. In this embodiment, the first metal surface treatment agent and the second metal surface treatment agent have the same composition, the difference being the content of trivalent chromium.

[0030] The second metal surface treatment agent consists of compound A containing trivalent chromium and compound B, wherein compound B is a film-forming vinyl resin; the mass ratio of metallic chromium in compound A to vinyl resin is 0.65. The ratio of the thickness of the film of the first metal surface treatment agent to the thickness of the film of the second metal surface treatment agent is 1.2:1.

[0031] The subsequent lamination process uses the pressure of existing technology. Compared with the metal surface treatment layer using the same thickness of first metal surface treatment agent or second metal surface treatment agent alone, it can be seen under a high magnification microscope or NMR that the aluminum substrate surface film layer using this technical solution has no cracks.

[0032] Example 2

[0033] A method for treating metal surfaces includes the following steps:

[0034] S1. Cleaning the stainless steel substrate surface. This cleaning process is a standard procedure in metal surface treatment, and the cleaning agents used are also standard products. No special requirements are specified here. All cleaning agents that can be used to clean stainless steel substrates are applicable. This step must include a water rinsing process. In addition, acid or alkali is not suitable for cleaning in this step because this technical solution is not suitable for causing a certain degree of micro-corrosion to the stainless steel substrate surface through the use of acid or alkali. That is, the stainless steel substrate surface treated by this technical solution is relatively smooth.

[0035] S2. After coating the cleaned stainless steel substrate with a 30nm thick first metal surface treatment agent, it is allowed to air dry at room temperature for 1 hour. In this embodiment, the first metal surface treatment agent consists of compound A containing trivalent chromium and compound B, wherein compound B is a film-forming vinyl resin; the mass ratio of metallic chromium in compound A to the vinyl resin is 0.25. In this embodiment, the exact structure of the vinyl resin is not required, as the focus of this technical solution is on the treatment method.

[0036] S3. A second metal surface treatment agent with a thickness of 22 nm is coated on the first metal surface treatment agent after natural drying, and then heated and dried at a temperature of 160°C to form a surface treatment film. In this embodiment, the first metal surface treatment agent and the second metal surface treatment agent have the same composition, the difference being the content of trivalent chromium.

[0037] The second metal surface treatment agent consists of compound A and compound B containing trivalent chromium, wherein compound B is a film-forming vinyl resin; the mass ratio of metallic chromium in compound A to vinyl resin is 0.8.

[0038] The subsequent lamination process uses the pressure of existing technology. Compared with the metal surface treatment layer using the same thickness of first metal surface treatment agent or second metal surface treatment agent alone, it can be seen under a high magnification microscope or NMR that the stainless steel substrate surface film layer using this technical solution has no cracks.

[0039] Example 3

[0040] A method for treating metal surfaces includes the following steps:

[0041] S1. Cleaning the surface of the aluminum alloy substrate. This cleaning process is a standard procedure in metal surface treatment, and the cleaning agents used are also standard products. No special requirements are specified here. All cleaning agents that can be used to clean the aluminum alloy substrate are applicable. This step must include a water cleaning process. In addition, acid or alkali is not suitable for cleaning in this step because this technical solution is not suitable for causing micro-corrosion on the surface of the aluminum alloy substrate through the use of acid or alkali. That is, the surface of the aluminum alloy substrate treated by this technical solution is relatively smooth.

[0042] S2. After coating the cleaned aluminum alloy substrate with a 30nm thick first metal surface treatment agent, it is allowed to air dry at room temperature for 1 hour. In this embodiment, the first metal surface treatment agent consists of compound A containing trivalent chromium and compound B, wherein compound B is a film-forming vinyl resin; the mass ratio of metallic chromium in compound A to the vinyl resin is 0.25. In this embodiment, the exact structure of the vinyl resin is not required, as the focus of this technical solution is on the treatment method.

[0043] S3. A second metal surface treatment agent with a thickness of 25 nm is coated on the first metal surface treatment agent after natural drying, and then heated and dried at a temperature of 160°C to form a surface treatment film. In this embodiment, the first metal surface treatment agent and the second metal surface treatment agent have the same composition, the difference being the content of trivalent chromium.

[0044] The second metal surface treatment agent consists of compound A and compound B containing trivalent chromium, wherein compound B is a film-forming vinyl resin; the mass ratio of metallic chromium in compound A to vinyl resin is 0.8.

[0045] The subsequent lamination process uses the pressure of existing technology. Compared with the metal surface treatment layer using the same thickness of first metal surface treatment agent or second metal surface treatment agent alone, it can be seen under a high magnification microscope or NMR that the stainless steel substrate surface film layer using this technical solution has no cracks.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for treating metal surfaces, characterized in that, Includes the following steps: S1. Clean the surface of the metal substrate; S2. After applying the first metal surface treatment agent to the cleaned metal substrate, allow it to air dry at room temperature for 0.5-1 hour. S3. Apply the second metal surface treatment agent onto the first metal surface treatment agent after it has dried naturally, and then heat and dry it at a temperature of 80-220℃ to form a surface treatment film. The first metal surface treatment agent and the second metal surface treatment agent have the same composition, the difference being the content of trivalent chromium. The first metal surface treatment agent is composed of compound A and compound B containing trivalent chromium, wherein compound B is a film-forming vinyl resin; The mass ratio of metallic chromium to vinyl resin in compound A containing trivalent chromium is 0.2-0.

25. The second metal surface treatment agent is composed of compound A and compound B containing trivalent chromium, wherein compound B is a film-forming vinyl resin; the mass ratio of metallic chromium in the trivalent chromium compound A to the vinyl resin is 0.35-0.8; The thickness of the first metal surface treatment agent film on the metal substrate surface is greater than the thickness of the second metal surface treatment agent film.

2. The metal surface treatment method according to claim 1, characterized in that, The mass ratio of metallic chromium to vinyl resin in the trivalent chromium compound A is 0.5-0.

8.

3. The metal surface treatment method according to claim 1, characterized in that, The metal substrate is made of stainless steel, aluminum, or aluminum alloy.

4. The metal surface treatment method according to claim 1, characterized in that, The ratio of the thickness of the first metal surface treatment agent film to the thickness of the second metal surface treatment agent film is 1.2-1.5:1.