WO2021027748A1

WO2021027748A1 - Electrolytic oxidation solution for use in aluminum alloy oxidative film formation, and method for aluminum alloy oxidative film formation

Info

Publication number: WO2021027748A1
Application number: PCT/CN2020/108026
Authority: WO
Inventors: 西华昆; 马康慷; 张祥华; 庄乾浩; 毕小雪; 杨维玉; 高瑞安
Original assignee: 临朐县检验检测中心; 高瑞安; 潍坊国一铝材有限公司
Priority date: 2019-08-12
Filing date: 2020-08-08
Publication date: 2021-02-18
Also published as: AU2020327479A1; CN110284174A; CN110284174B; AU2020327479B2

Abstract

Disclosed are an electrolytic oxidation solution for use in aluminum alloy oxidative film formation, and a method for aluminum alloy oxidative film formation. The electrolytic oxidation solution comprises the following components: 0.1-1 g/L of ammonium hydrogen difluoride, and 5-60 g/L of oxalic acid, the oxidation solution comprising Al ³⁺ at a balanced concentration of 0.01-1 g/L. The method for aluminum alloy oxidative film formation comprises conducting an electrolytic process using the above electrolytic oxidation solution to form a layer of organic and inorganic fluorine-containing oxidation film on a surface of an aluminum alloy by means of a synergistic action of chemical film formation and electrochemical film formation. Use of the electrolytic oxidation solution according to the present invention to conduct film formation by electrolytic oxidation can achieve a fast film formation process due to the synergistic action of chemical film formation and electrochemical film formation. An ionization equilibrium will generally occur when an aluminum ion concentration in the oxidation solution reaches about 0.1 g/L, such that the aluminum ion concentration no longer increases. Therefore, the oxidation solution can be recycled instead of being changed, and thus produces less solid waste in comparison to the prior art.

Description

Electrolytic oxidation solution used for aluminum alloy oxidation film formation and aluminum alloy oxidation film formation method

Technical field

The invention relates to the technical field of surface treatment of aluminum alloy profiles, in particular to a treatment technology using electrochemical oxidation to form a film.

Background technique

The surface oxidation treatment of aluminum alloy is mainly to generate a protective film on the surface of the aluminum profile. This layer of film has protective, decorative and some other functional characteristics to meet the needs of aluminum anodizing for construction, aluminum anodizing for decoration, aluminum anodizing for corrosion protection, and aluminum anodizing for engineering. According to different purposes of use and different performance requirements, make full use of the characteristics of the film to meet different purposes.

According to the different electrolytes in the prior art, barrier type anodic oxide film electrolytes are roughly divided into: boric acid, neutral borate, neutral phosphate, neutral tartrate, neutral citrate, and neutral oxalic acid Salt; porous anodic oxide film electrolyte: sulfuric acid, oxalic acid, chromic acid, phosphoric acid, sulfuric acid plus organic acid, etc.

The porous oxidizing electrolyte in the prior art has the problem that the aluminum ions in the solution continue to rise as the electrolysis time is extended. In order to control the concentration of aluminum ions in the electrolyte, the electrolyte must be continuously discharged to supplement the electrolyte without aluminum ions. Maintain the aluminum ion concentration range.

The oxidation film formation process in the existing technology is as follows:

Forming process _{_{2Al + 3H 2 O → Al 2}} O 3 + 6H + + 6e -

Film dissolution process Al ₂ O ₃ +6H ⁺ →2Al ³⁺ +3H ₂ O

The separation of water on the cathode produces gas:

_{^{6H 2 O + 6e - → 3H}} 2 ↑ + 6OH -

Taking sulfuric acid as an example, the anion SO ₄ ^2- participates in the anodic reaction process of aluminum, and finally produces an anodic oxide film containing sulfate:

2Al+6H ⁺ →2Al ³⁺ +3H ₂ ↑

2Al ³⁺ +3H ₂ O+3SO ₄ ^2- →【Al ₂ O ₃ 】+3H ₂ SO ₄

Al ³⁺ +XH ₂ O+YSO ₄ ^2- →【Al(OH) _Y (SO ₄ ) _X 】+XH ⁺

This is a process of continuous film formation and dissolution.

During the above oxidation process, if the concentration of F ^- and Cl ^- in the solution exceeds 50μg/g, corrosion spots will appear on the profile, so it must be strictly controlled.

No matter what kind of porous oxide film production process is used above, the aluminum ion concentration in the electrolyte will continue to increase. Generally speaking, it will have a beneficial effect if it is below 10g/L, and it will have an adverse effect if it exceeds 10g/L. In order to control the aluminum ion concentration, the method of discharging part of the old bath is generally used to reduce the aluminum content. The discharge of the electrolyte takes away a large amount of H ₂ SO ₄ , and AI ³⁺ causes pollution to the environment. Most of them are neutralized by lime, so a large amount of Of solid waste, causing tremendous pressure on the environment. The existing technology is not conducive to environmental protection, is also a key process point for the current aluminum profile enterprises to generate a large amount of solid waste, and increases production costs.

Summary of the invention

The first technical problem to be solved by the present invention is to provide an electrolytic oxidizing solution for aluminum alloy oxidation film formation in view of the shortcomings of the prior art. The aluminum ion concentration generally reaches about 0.1g/L to produce ionization balance. The oxidizing solution does not need to be replaced and can be recycled. The generated oxide film is an organic and inorganic fluorine-containing oxide film, which has a honeycomb-like uniform oxide film with corrosion resistance, impact resistance, high hardness and high wear resistance.

The second technical problem to be solved by the present invention is: in view of the shortcomings of the prior art, an aluminum alloy oxidation film forming method is provided, the process method is simple, the electrolyte waste does not need to be replaced, and the environmental protection problem is solved.

To solve the above-mentioned first technical problem, the technical solution of the present invention is:

An electrolytic oxidizing solution for aluminum alloy oxidation and film formation, the electrolytic oxidizing solution contains the following components: hydrogen fluoride ammonia 0.1-1g/L, oxalic acid 5-60g/L; Al ³⁺ equilibrium solubility in the oxidizing solution It is 0.01～1g/L.

As a preferred technical solution, the electrolytic oxidation solution contains the following components: 0.1～0.6g/L of hydrogen fluoride ammonia, 10～40g/L of oxalic acid; the equilibrium solubility of Al ^{3+ in} the oxidation solution is 0.01～1g /L.

The presence of F ions in the electrolytic oxidation solution of the present invention reduces the chemical energy of AI and makes it easier to generate AI ^3+. The concentration of oxalic acid is about 50 times that of ammonium hydrogen fluoride, and it also ensures that AI ³⁺ can generate aluminum oxalate and participate in film formation. F ions also act as catalysts during the reaction. The strong complexation of F ions on Al ³⁺ accelerates the dissolution of the oxide film and the continuous formation of porous oxide film layers. Oxalic acid participates in the joint process of anodic oxide film formation-anodic oxidation-chemical dissolution-chemical film formation. However, if the concentration of NH ₃ HF reaches about 1.5 g/l, it will become a film dissolving effect. When the film thickness reaches about 10μm, the film-forming solution reaches equilibrium, and the film will no longer increase; when it is increased to about 5.0g/l, the film-forming film will be larger than the film-forming in the oxidation process, and the oxide film cannot be formed and lead to the concentration of AI ^{3+ in the} solution Keep rising. The dissolution of the aluminum matrix mainly depends on the concentration of fluoride ion, and the film formation depends on oxalic acid. By coordinating the ratio of the two, the balance of dissolution and film formation can be achieved, and the Al ³⁺ concentration of the system pretreatment system can be maintained basically unchanged.

As an improved technical solution, the electrolytic oxidation solution also contains one or more of soluble fluoride salt, oxalate and sulfate. The added amount of the fluoride salt, oxalate salt and sulfate salt is 0.1-60 g/L.

As a preferred technical solution, the electrolytic oxidation solution also contains one or more of sodium fluoride, sodium oxalate and sodium sulfate. The addition of sodium fluoride and sodium oxalate can effectively increase the content of organic components in the oxide film and aluminum hexafluoride salt, aluminum trifluoride, and sulfate can also participate in film formation, and the addition of salt can also reduce electrical resistance and reduce electrolysis energy consumption.

To solve the above-mentioned second technical problem, the technical solution of the present invention is:

An aluminum alloy oxidation film formation method uses the above-mentioned electrolytic oxidation solution and an electrolysis method to form an organic-inorganic fluorine-containing oxide film on the surface of the aluminum alloy through chemical film formation and electrochemical film formation.

As an improved technical solution, the constant-voltage method is used for electrolysis during the electrolysis, and the voltage during the electrolysis by the constant-voltage method is 20-60v.

As another improved technical solution, the constant current method is used for electrolysis during the electrolysis, and the current during the constant current electrolysis is 1 to 5 A/dm ² .

As a preferred technical solution, the electrolysis time during the electrolysis is 1 min-6h.

As a preferred technical solution, the organic-inorganic fluorine-containing oxide film has a thickness of 0.5-60 μm.

Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

The electrolytic oxidizing solution used for the oxidation of aluminum alloy film of the present invention contains the following components: hydrogen fluoride ammonia 0.1 to 1 g/L, oxalic acid 5 to 60 g/L; Al ³⁺ equilibrium dissolved in the oxidizing solution The degree is 0.01～1g/L. The electrolytic oxidizing solution of the present invention is used for electrolytic oxidation to form a film, chemical film forming and electrochemical film forming work together, and the film forming process is fast; the aluminum ion concentration in the oxidizing solution is generally about 0.1g/L, that is, ionization balance occurs, and the aluminum ion concentration is not It is increased again, so the oxidizing liquid does not need to be replaced and can be recycled. Therefore, compared with the prior art, the solid waste is reduced. For every 5,000 tons of profiles produced, about 50 tons of Al ^{3+ are} discharged, which reduces wastewater discharge by more than 80% and reduces wastewater consumption More than 90% oxygen. Moreover, the oxide film produced by the electrolysis of the present invention is an organic-inorganic fluorine-containing oxide film. After SEM+EDS detection and analysis, the oxide film has a uniform honeycomb shape, and the film porosity is above 60%. Among them, the fluorine content is 1-15%, the C content is 3-20%; the O content is about 46%, and the formed film has the advantages of high corrosion resistance, high impact resistance, toughness, high hardness and high wear resistance, and the film hardness Around 400HV.

The present invention adopts the electrolytic oxidation solution oxidation film forming method, which is simple, easy to control, and fast in film forming speed. Constant voltage electrolysis or constant current electrolysis can be used, both of which can quickly obtain a uniformly formed honeycomb oxide film , The electrolysis time is 1-20 minutes to get an oxide film with a thickness of 5-20μm. Moreover, after long-term tests, the electrolyte Al ion in the electrolyte is about 0.1g/L, which produces an electrolytic balance. The aluminum ion concentration will not increase over 12 months, and the low electrolyte concentration is used, and the fluoride ion is used as the electrolytic film to dissolve the film. Agent (porolytic agent), interferes with the phenomenon of local interference (such as pitting) caused by other ions on the surface of the anodic anodized film. The qualitative change of the chemical film formation and the electrochemical film formation can reduce the influence of the concentration on the film formation. Large current can be used to quickly form a film to reduce oxidation costs.

The electrolysis method of the present invention can obtain a colorless transparent to golden yellow composite film by controlling the voltage and current density, controlling the film forming speed, and changing the film forming composition.

Description of the drawings

The present invention will be further described below in conjunction with the drawings and embodiments.

Figure 1 is a surface topography of an oxide film with a thickness of 15 μm detected by SEM of the present invention;

Fig. 2 is a surface topography of an oxide film with a thickness of 20 μm detected by SEM of the present invention;

Figure 3 is an EDS analysis energy spectrum of a certain point in Figure 1;

Figure 4 is an EDS analysis energy spectrum diagram of another point in Figure 1;

Figure 5 is an EDS analysis energy spectrum of a certain point in Figure 2;

Figure 6 is an EDS analysis energy spectrum diagram of another point in Figure 2;

Figure 7 is an XPS spectrum of a certain point in Figure 1.

detailed description

The present invention will be further explained below in conjunction with the drawings and embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

As shown in Figures 1-2, the pore diameter of the oxide film produced by the electrolysis of the present invention is in a uniform honeycomb shape below 100nm; EDS analysis is performed on any two points in Figures 1 and 2 with thicknesses of 15μm and 20μm respectively; Corresponding to the energy spectra of Figure 3, Figure 4, Figure 5 and Figure 6, the analysis results are shown in Table 1, Table 2, Table 3 and Table 4 below. It can be seen from the figure that the C on the surface of the oxide film of the present invention mainly exists in the form of functional groups such as CC, CO, C=O, and F is in the form of AlF3/Na3AlF6; thus, it is proved that the oxide film of the present invention has chemical film formation process.

Table 1

Table 2

table 3

Table 4

According to GB/T 9790-1988 and GB/T12967.3-2008, the corrosion resistance and microhardness of the conventional sulfuric acid film of the prior art and the aluminum alloy oxide film of the present invention were tested. The results are shown in Table 5 below.

It can be seen that under the premise of a smaller thickness, the oxide film prepared by the present invention has higher hardness and stronger corrosion resistance.

Example 1

An electrolytic oxidizing solution used for aluminum alloy oxidation film formation, the electrolytic oxidizing solution contains the following components: hydrogen fluoride ammonia 0.2g/L, oxalic acid 10g/L; the equilibrium solubility of Al ^{3+ in} the oxidizing solution is 0.1g /L.

Example 2

An electrolytic oxidizing solution used for aluminum alloy oxidation film formation, the electrolytic oxidizing solution contains the following components: hydrogen fluoride ammonia 0.4g/L, oxalic acid 20g/L; the equilibrium solubility of Al ^{3+ in} the oxidizing solution is 0.2g /L.

Example 3

An electrolytic oxidizing solution for aluminum alloy oxidation and film formation, the electrolytic oxidizing solution contains the following components: hydrogen fluoride ammonia 0.6g/L, oxalic acid 30g/L; the equilibrium solubility of Al ^{3+ in} the oxidizing solution is 0.22g /L.

Example 4

An electrolytic oxidation solution containing the following components is used: 0.5 g/L of hydrogen fluoride ammonia, 35 g/L of oxalic acid, and 2 g/L of sodium fluoride; the equilibrium solubility of Al ^{3+ in} the oxidation solution is 0.2 g/L. Under normal temperature, electrolysis is carried out with a direct current density of 2.5A/dm ² (constant current method), and the electrolysis time is 10 minutes.

Example 5

An electrolytic oxidation solution containing the following components is used: 0.6 g/L of hydrogen fluoride ammonia and 40 g/L of oxalic acid; the equilibrium solubility of Al ^{3+ in} the oxidation solution is 0.18 g/L. Under normal temperature, the electrolysis is carried out with a DC current density of 3.0A/dm ² (constant current method), and the electrolysis time is 15 minutes.

Example 6

An electrolytic oxidation solution containing the following components is used: 0.45 g/L of hydrogen fluoride ammonia, 30 g/L of oxalic acid, and 5 g/L of sodium oxalate; the equilibrium solubility of Al ^{3+ in} the oxidation solution is 0.2 g/L. Under normal temperature, the electrolysis is carried out with a DC voltage of 40v (constant voltage method), and the electrolysis time is 15 minutes.

Example 7

An electrolytic oxidation solution containing the following components is used: 0.55 g/L of hydrogen fluoride ammonia and 35 g/L of oxalic acid; the equilibrium solubility of Al ^{3+ in} the oxidation solution is 0.2 g/L. Under normal temperature, the electrolysis is carried out with a DC voltage of 30v (constant voltage method), and the electrolysis time is 20 minutes.

Example 8

An electrolytic oxidation solution containing the following components is used: 0.35 g/L of hydrogen fluoride ammonia and 38 g/L of oxalic acid; the equilibrium solubility of Al ^{3+ in} the oxidation solution is 0.21 g/L. Under normal temperature, the electrolysis is carried out with a DC voltage of 60v (constant voltage method), and the electrolysis time is 30min.

Comparative example 1

Electrolytically oxidizing the prior art solution using sulfuric acid, a sulfuric acid concentration of electrolyte 18g / L, a temperature of 18 ℃ ± 1, current density of 1.5A / dm ^2, the electrolysis time was 30min.

The thickness and hardness of the oxide films prepared in the foregoing Examples 4-8 and Comparative Example 1, as well as the surface morphology and composition of the film detected and analyzed by SEM+EDS are shown in Table 5.

table 5

It can be seen from Table 5 that the oxide films prepared by the present invention are all uniform honeycomb, with a porosity of more than 65%, and are organic-inorganic combined fluorine-containing oxide films with high hardness. And within a certain range, as the electrolysis time increases, the film thickness increases. The comparative example obtained an inorganic film without honeycomb and fluorine. The film porosity is only 18% and the hardness is low.

Industrial applicability

1. The electrolytic oxidizing solution used for the oxidation and film formation of aluminum alloy of the present invention contains the following components: hydrogen fluoride ammonia 0.1-1g/L, oxalic acid 5-60g/L; Al ^{3+ in} the oxidizing solution The equilibrium solubility is 0.01～1g/L. The electrolytic oxidizing solution of the present invention is used for electrolytic oxidation to form a film, chemical film forming and electrochemical film forming work together, and the film forming process is fast; the aluminum ion concentration in the oxidizing solution is generally about 0.1g/L, that is, ionization balance occurs, and the aluminum ion concentration is not It is increased again, so the oxidizing liquid does not need to be replaced and can be recycled. Therefore, compared with the prior art, the solid waste is reduced. For every 5,000 tons of profiles produced, about 50 tons of Al ^{3+ are} discharged, which reduces wastewater discharge by more than 80% and reduces wastewater consumption The oxygen content is more than 90%, so it has good industrial applicability.

2. The oxide film produced by the electrolysis of the present invention is an organic-inorganic fluorine-containing oxide film. After SEM+EDS detection and analysis, the oxide film has a uniform honeycomb shape, and the film porosity is above 60%. Among them, the fluorine content is 1-15%, the C content is 3-20%; the O content is about 46%, and the formed film has the advantages of high corrosion resistance, high impact resistance, toughness, high hardness and high wear resistance, and the film hardness Around 400HV, it has good industrial applicability.

3. The present invention uses the electrolytic oxidation solution to oxidize and form a film. The method is simple, easy to control, and the film formation speed is fast. Constant voltage electrolysis or constant current electrolysis can be used, and uniformly formed honeycombs can be quickly obtained. Oxide film, the electrolysis time is 1-20 minutes to get an oxide film with a thickness of 5-20μm. The colorless transparent to golden yellow composite film can be obtained by controlling the voltage and current density, controlling the film forming speed, and changing the film composition. The process method is simple and controllable, so it has good industrial applicability.

4. After long-term test, the electrolyte Al ion in the electrolyte will produce electrolytic equilibrium at about 0.1g/L, and the aluminum ion concentration will not increase over 12 months, and the low electrolyte concentration is used, and the fluoride ion is used as the electrolytic oxide film. Membrane agent (porolytic agent), interferes with the phenomenon of local interference (such as pitting) caused by other ions on the surface of anodized film, chemical film formation, electrochemical film formation, and qualitative change together, reducing the influence of concentration on film formation, and High current can also be used to quickly form a film to reduce oxidation costs, so it has good industrial applicability.

Claims

An electrolytic oxidizing solution used for aluminum alloy oxidation film formation, characterized in that the electrolytic oxidizing solution contains the following components: hydrogen fluoride ammonia 0.1-1g/L, oxalic acid 5-60g/L; Al 3+ in the oxidizing solution The equilibrium concentration is 0.01～1g/L.
The electrolytic oxidizing solution used for aluminum alloy oxidation film formation according to claim 1, wherein the electrolytic oxidizing solution contains the following components: hydrogen fluoride ammonia 0.1-0.6g/L, oxalic acid 10-40g/L; The equilibrium solubility of Al 3+ in the oxidation solution is 0.1 to 1 g/L.
The electrolytic oxidation solution for aluminum alloy oxidation film formation according to claim 1, wherein the electrolytic oxidation solution further contains one or more of soluble fluoride salt, oxalate and sulfate.
The electrolytic oxidizing solution for aluminum alloy oxidation film formation according to claim 3, characterized in that: the electrolytic oxidizing solution further contains one or more of sodium fluoride, sodium oxalate and sodium sulfate.
An aluminum alloy oxidation film forming method, characterized in that: using the electrolytic oxidation solution of any one of claims 1 to 4, an electrolytic method is used to form a film on the surface of the aluminum alloy through the combined action of chemical film formation and electrochemical film formation Layer organic and inorganic fluorine-containing oxide film.
5. The aluminum alloy oxidation film forming method according to claim 5, wherein the constant voltage method is used for electrolysis during the electrolysis, and the voltage during the electrolysis by the constant voltage method is 20-60v.
The aluminum alloy oxidation film forming method according to claim 5, wherein the constant current method is used for electrolysis during the electrolysis, and the current during the constant current electrolysis is 1 to 5 A/dm 2 .
The aluminum alloy oxidation film forming method according to claim 5, wherein the electrolysis time during the electrolysis is 1 min-6h.
The method for forming an aluminum alloy oxide film according to claim 5, wherein the thickness of the organic-inorganic fluorine-containing oxide film is 0.5-60 μm.