CN101498026B - Electrolyte for anodic oxidation treatment of magnesium alloy and method for surface treatment of magnesium alloy - Google Patents

Abstract

Translated fromChinese

本发明涉及一种镁合金阳极氧化处理的电解液及对镁合金表面处理的方法，所述电解液的组成为：聚天冬氨酸20-60ml/L、硅酸盐40-100g/L、氢氧化物15-60g/L，添加剂为植酸、植酸盐、柠檬酸、柠檬酸盐、草酸、草酸盐中的任意一种，其中，植酸或植酸盐浓度为3-15g/L，柠檬酸或柠檬酸盐浓度为5-20g/L，草酸或草酸盐浓度为5-20g/L，所述电解液的pH为10-13。采用本发明所述的电解液对镁合金进行阳极氧化表面处理，其工艺简单，成膜过程易于控制，在镁合金的表面能生成光滑、均匀、耐腐蚀好的氧化层，并且电解液不会造成环境污染，具有推广应用的价值。The invention relates to an electrolyte solution for anodic oxidation treatment of magnesium alloys and a method for treating the surface of magnesium alloys. The composition of the electrolyte solution is: polyaspartic acid 20-60ml/L, silicate 40-100g/L, Hydroxide 15-60g/L, the additive is any one of phytic acid, phytate, citric acid, citrate, oxalic acid, and oxalate, wherein the concentration of phytic acid or phytate is 3-15g/L L, the concentration of citric acid or citrate is 5-20g/L, the concentration of oxalic acid or oxalate is 5-20g/L, and the pH of the electrolyte is 10-13. Using the electrolytic solution of the present invention to carry out anodic oxidation surface treatment on magnesium alloy, the process is simple, the film forming process is easy to control, and a smooth, uniform and corrosion-resistant oxide layer can be formed on the surface of magnesium alloy, and the electrolytic solution will not Cause environmental pollution, has the value of popularization and application.

Description

Electrolytic solution that anodic oxidation of magnetism alloy is handled and the method that Mg alloy surface is handled

Technical field

The present invention relates to a kind of magnesium alloy surface treatment, particularly a kind ofly can generate the method that the anodic oxidation of magnetism alloy of smooth, even, fine and close, corrosion-resistant ceramic layer is handled electrolytic solution and Mg alloy surface is handled at Mg alloy surface.

Background technology

Magnesium alloy is one of the lightest structural metallic materials, integrates numerous advantages, has broad application prospects.But the activity of magnesium alloy is strong, poor corrosion resistance.Therefore, surface treatment method becomes people and improves corrosive nature quick of magnesium alloy and effective measures.Wherein, anodic oxidation of magnetism alloy is the treatment technology of effective surface the most that improves the magnesium alloy corrosive nature.Anodic oxidation is to utilize electrochemical method to produce one deck stable oxide rete at metal and alloy surface thereof, because rete has vesicular structure, can increase the erosion resistance of magnesium alloy by japanning, dyeing, sealing of hole or Passivation Treatment.Anodised advantage be anode oxide film at the matrix surface growth in situ, have and matrix metal bonding strength height, advantage such as wear-resistant, corrosion-resistant.

So far, the fast development of anodic oxidation of magnetism alloy technology has obtained gratifying achievement.From the development of anodic oxidation of magnetism alloy, its electrolytic solution and technology constantly develop towards environment-friendly type, have mainly experienced three phases:

(1) as far back as the 1950's, the anodizing technology of magnesium alloy is just succeeded in developing, and mainly contains HAE, Dow17, GEC, Cr-22 etc.Typical technology is HAE and Dow17 method, still is extensive use of so far.HAE is a kind of anode oxidation method of magnesium alloy most worthy in basic solution, and Dow17 is magnesium alloy most widely used a kind of anode oxidation method in acidic solution.Because anodic oxidation of magnetism alloy liquid has used the toxic compounds that contains chromium more in these methods, therefore, the shortcoming of aforesaid method is a contaminate environment, the processing cost height of waste liquid.

(2) 20 eighties in century, the Chrome-free anodic oxidation becomes the new trend that people are developed anodic oxidation of magnetism alloy gradually, and using more typical process has Zelanian Anomag method, German Magoxid-coat method, the Tagnite method of the U.S., the UBE-5 method of Japan etc.Though these method anodic oxidation of magnetism alloy liquid do not contain Cr⁶⁺, but still contain environmentally harmful F^-, PO₄^3-Ion.

(3) the early 21st century, no Cr⁶⁺, F^-, PO₄^3-Ionic anodic oxidation of magnetism alloy liquid and technical study thereof become research emphasis.Wherein magnesium alloy anodic oxidation electrolyte is divided into acid system and alkaline system two classes.Acid system often contains chromium or phosphorus or fluorine, does not meet environmental requirement, and therefore, the main alkalitropism electrolytic solution of the research of environment protection type anodic oxidation technology is in the foundational system, adds additive, improves the over-all properties of anode oxide film.The alkaline electrolyte of anodic oxidation of magnetism alloy mainly contains NaOH-Na at present₂SiO₃-Na₂B₄O₇, NaOH-Na₂SiO₃-NaAlO₂, NaOH-Na₂SiO₃, NaOH-Na₂B₄O₇, NaOH-carboxylate salt, Na₂B₄O₇-Na₂SiO₃, NaOH-Al (OH)₃-Na₂SiO₃Etc. system.Alkaline electrolyte concentrates on silicate and aluminate two big series.Silicate is solution-stabilized, can promote the oxidation of matrix alloy, and forms insoluble compound, makes rete refinement, hard, fine and close, improves homogeneity, can significantly strengthen the solidity to corrosion of rete, also can increase rete gloss.Aluminate-series can promote the film growth, makes the oxidation film layer densification, reduces from corrosion current, improves corrosion resisting property, also helps rete to thicken, and surface irregularity reduces, but the alkaline electrolyte of aluminate is wayward, and solution is easily muddy, greatly influences film-formation result.During anodic oxidation of magnetism alloy, removing needs to select electrolytic solution also to need to control anodised processing condition simultaneously.Usually the optimum process condition of anodic oxidation of magnetism alloy can change along with the variation of electrolytic solution kind and concentration.Wherein processing parameters such as electric source modes, electric current, voltage, stirring, time, temperature have determined the various performances of anode oxide film.At present, electric source modes mainly contains dc electrolyzing method, ac oxide method and pulse oxidizes method etc.Wherein, dc electrolyzing method technology is simple, and is easy to control.Constant current mode reduces non-homogeneous film forming possibility than constant voltage mode anode oxidation process more easy to control, improves the speed of growth, so sees constant current control in the anodic oxidation of magnetism alloy more.The representational patent of this stage anodic oxidation of magnetism alloy has: " magnesium and magnesium alloy environment protection type anodic oxidation electrolytic liquid and application thereof " (the notification number CN01114075) of the Zhang Yongjun of Metal Inst., Chinese Academy of Sciences, " a kind of environmental-protection type magnesium alloy differential arc oxidation electrolytic solution and differential arc oxidation method " (the notification number CN 200410100411) of the Zhang Rongfa of Metal Inst., Chinese Academy of Sciences.Though these method anodic oxidation of magnetism alloy have been realized no Cr⁶⁺, F^-, PO₄^3-The ionic environmental requirement, but environmental-protection type magnesium alloy anodic oxidation electrolyte and method thereof be ubiquity electrolytic solution instability, easy precipitation also, the difficult control of film process, sticking power is not strong, and film forming is inhomogeneous, easily produces local the ablation and seminess, solidity to corrosion is poor, problems such as apparent colour is abundant, and current efficiency is low are difficult to satisfy the various application needs of magnesium alloy.

Summary of the invention

At above problem, the purpose of this invention is to provide a kind of electrolytic solution of anodic oxidation of magnetism alloy processing and the method that Mg alloy surface is handled, adopt electrolytic solution of the present invention that magnesium alloy is carried out surface treatment, its technology is simple, film process is easy to control, generate smooth, even, corrosion-resistant good zone of oxidation at the surface energy of magnesium alloy, and electrolytic solution can not cause environmental pollution, have the value of applying.

For achieving the above object, implementation is as follows:

Consisting of of the electrolytic solution of anodic oxidation of magnetism alloy: poly aspartic acid 20-60ml/L, alkalimetal silicate 40-100g/L, oxyhydroxide 15-60g/L, additive is any one in phytic acid, phytate, Citrate trianion, oxalic acid, the oxalate, wherein, phytic acid or phytate concentration are 3-15g/L, citric acid or citric acid salt concentration are 5-20g/L, oxalic acid or concentration of oxalate are 5-20g/L, and the pH of described electrolytic solution is 10-13.Used electrolytic solution all adopts distilled water to be mixed with the aqueous solution.

What described electrolytic solution was more excellent consists of: poly aspartic acid 40ml/L, silicate 60-80g/L, oxyhydroxide 30-45g/L, additive is any one in phytic acid, phytate, citric acid, Citrate trianion, oxalic acid, the oxalate, wherein, phytic acid or phytate concentration are 3-15g/L, citric acid or citric acid salt concentration are 5-20g/L, oxalic acid or concentration of oxalate are 5-20g/L, and the pH of described electrolytic solution is 10-13.

Oxyhydroxide of the present invention be in sodium hydroxide, the potassium hydroxide any one, described alkalimetal silicate is water glass or potassium silicate.

Additive of the present invention is phytic acid or basic metal phytate, and wherein phytate is sodium phytate or POTASSIUM PHYTATE.

The contained additive of the present invention can be citric acid or alkali metal citrate, and wherein alkali metal citrate is Trisodium Citrate or Tripotassium Citrate.

Additive of the present invention can also be oxalic acid or basic metal oxalate, and wherein the basic metal oxalate is sodium oxalate or potassium oxalate.

The effect of each reagent of the present invention is as follows: caustic alkali is the main component of alkaline anodic oxidation electrolyte, is used for the pH value of regulator solution and the hardness of raising zone of oxidation.Silicate is main membrane-forming agent in alkaline anodic oxidation electrolyte, is used to promote the oxidation of matrix alloy, and forms insoluble compound, makes rete refinement, hard, fine and close, improves homogeneity, can significantly strengthen the solidity to corrosion of rete, and also can play increases rete gloss.Poly aspartic acid (PASP) has corrosion inhibition and feature of environmental protection dual function, it is a water-soluble polymers, be alkalescence, it is a kind of novel green water conditioner, characteristic with without phosphorus, nontoxic, nuisanceless and fully biodegradable has extremely strong sequestering power to ion, and PASP has dissemination simultaneously and can effectively prevent the corrosion of hardware, the alternative phosphorated water conditioner of PASP is with eutrophication and the discharging secondary pollution of avoiding water body.PASP is a kind of to suppress the inhibiter of anode, and corrosion inhibition rate can be up to 80.33%.In the present invention, PASP can use in the anticorrosion and anodised electrolytic solution of magnesium alloy.Experiment showed, that PASP not only has corrosion inhibition to magnesium alloy, also promoter action is arranged forming corrosion resistant anodic oxidation of magnetism alloy film.Phytic acid be the good inhibiter of metal be again metal finishing ideal sequestrant, the adding of phytic acid helps the raising of arc voltage, if it is excessive then surface film can become uneven loose porous to add concentration, so the concentration of phytic acid is unsuitable too high.Citric acid or Citrate trianion can provide the controlled arc light that moves about, and prevent that pitting from forming.Oxalic acid or basic metal oxalate can play coordination, buffered effect, and the while can be improved film hardness and be made the main component of film layer structure densification.

Adopt the step of electrolytic solution processing magnesium alloy of the present invention as follows:

A. magnesium alloy pre-treatment: boring, polishing, tap water clean, distilled water cleans, acetone is ultrasonic, distilled water cleans, dry up preservation.

B. anodic oxidation of magnetism alloy: with stainless steel is negative electrode, and magnesium alloy is an anode, under the agitation condition, and constant voltage direct current,current density 10～30mA/cm², temperature is less than 40 ℃, and the time is 10～30min.

Electric current can also adopt interchange, pulse power source control, carries out anodic oxidation of magnetism alloy, also can reach effect of the present invention.

Current density of the present invention is controlled in 10～30mA/cm², magnesium alloy can obtain erosion resistance and good appearance has both anode oxide film.

Time of the present invention is controlled in 10～30min.Time is difficult for long or too short, if long, the roughness of anodic oxidation of magnetism alloy film increases, corrosion-resistant decline; If too short, film forming is incomplete, covers inhomogeneous, fine and close.

The present invention adopts the 85-2 model constant temperature blender with magnetic force of all over the country company limited in Shenzhen to stir.Stir in the anode oxidation process and can reduce diffusion mass transfer, provide competent oxygen, be beneficial to the anodic oxidation of magnetism alloy film forming to electrochemical reaction to film forming influence.

Temperature control of the present invention is with water-bath mode on the rocks.Electrolyte temperature is difficult for too high or too low, if too high, anodic oxidation of magnetism alloy film outward appearance is more coarse, and obvious crackle is arranged, and easily causes oxide film to come off, and erosion resistance descends; If low excessively, become layer-growth rate slow.

Can obtain the surface with distilled water cleaning having carried out surface-treated magnesium alloy and have magnesium alloy smooth, even, fine and close, the corrosion-resistant ceramic layer.

The present invention compared with prior art mainly contains following advantage:

(1) environmental protectionization.Realized no Cr⁶⁺, F^-, PO₄^3-The ionic anodic oxidation of magnetism alloy, assurance has operator's health, and waste liquid is handled easily simultaneously, and free from environmental pollution, toxicity is little, for anodic oxidation of magnetism alloy provides using value to environment-friendly type, non-harmful industrialization direction.

(2) the anodic oxidation of magnetism alloy film that antiseptic property is good.The anodic oxidation of magnetism alloy film good combination property of the present invention preparation, outward appearance is canescence, and smooth, even, fine and close, strong adhesion, corrosion resistance nature are good.The about 5-40 μ of thickness m is vesicular structure, can be organic coating, other retes provide good substrate, but the also follow-up use of sealing of hole.

(3) anode oxidation process is simple, stable, easy to control.

Reagent of the present invention adopts the commercial reagent, the product of the same name that poly aspartic acid (PASP) adopts Shandong Taihe Water Treatment Co., Ltd. to produce.

Description of drawings

Fig. 1 is the Tafel polarization curve through the inventive method surface-treated magnesium alloy sample and AZ31 magnesium alloy plate matrix; Among the figure, A is without anodised magnesium alloy sample curve; B: the anodic oxidation of magnetism alloy sample profile after the inventive method is handled.

Embodiment:

Embodiment 1:

Magnesium alloy materials: AZ31 magnesium alloy plate

Hole after above-mentioned magnesium alloy materials made 5 samples, polishing, tap water cleans, distilled water cleans, acetone is ultrasonic, distilled water cleans, dries up pre-treatment.

The anodic oxidation in the described electrolytic solution of table 1 of above-mentioned 5 magnesium alloy samples, the technology of oxidation: direct supply, constant current mode, current density are 20mA/cm², adopting water-bath mode on the rocks to control electrolyte temperature is 20～35 ℃, treatment time 30min.Whole anode oxidation process carries out under agitation condition.

Film forming result: see Table 1.

Table 1 electrolytic solution is formed and the film forming situation

Embodiment 2:

Magnesium alloy materials: AZ31 magnesium alloy plate

Hole after magnesium alloy materials made 4 samples, polishing, tap water cleans, distilled water cleans, acetone is ultrasonic, distilled water cleans, dries up pre-treatment.

The anodic oxidation in the described electrolytic solution of table 2 of above-mentioned 4 magnesium alloy samples, anodic oxidation condition: direct supply, constant current mode, current density are 20mA/cm², adopting water-bath mode on the rocks to control electrolyte temperature is 20～35 ℃, treatment time 30min.Whole anode oxidation process carries out under agitation condition.

Table 2 electrolytic solution is formed

The performance evaluation of anodic oxidation of magnetism alloy film: see Table 3.

Table 3 anodic oxidation of magnetism alloy film forming result

After adding PASP, the striking voltage of electrolytic solution obviously raises, and it is tiny intensive that spark becomes, and outward appearance has had very big variation, and it is complete, even that oxide film becomes.In these 4 samples, outward appearance is preferably No. 1 sample, No. 2 samples and No. 4 samples.

As seen from Table 3, the Tafel polarization curve that is used in 3.5% sodium chloride solution is estimated the anode oxide film corrosion resistance nature fast.Judgement criteria is that corrosion electric current density is more little, and polarization resistance Rp is big more, corrosion potential E_CorrHigh more, the corrosion resistance nature of anode oxide film is just good more.The polarization resistance Rp of No. 4 sample anodes oxide films will exceed that other four samples are a lot, and corrosion electric current density is minimum, and corrosion potential also is the highest, and No. 4 sample erosion resistances of the AZ31 magnesium alloy after anodic oxidation are the strongest.

Embodiment 3:

Electrolytic solution is formed:

NaOH：45g/L

Na₂SiO₃：100g/L

PASP：40ml/L

Phytic acid: 10.74g/L

Magnesium alloy materials: AZ31 magnesium alloy plate

Hole after magnesium alloy materials made sample, polishing, tap water cleans, distilled water cleans, acetone is ultrasonic, distilled water cleans, dries up pre-treatment.

Magnesium alloy sample anodic oxidation in above-mentioned electrolytic solution, anodic oxidation condition: direct supply, constant current mode, current density 10mA/cm², anodizing time 20min, to adopt water-bath mode on the rocks to control electrolyte temperature be 3 grades of 20 ℃, stirring velocity.Whole anode oxidation process carries out under agitation condition.

Film forming and results of property: the anodic oxidation of magnetism alloy film is canescence, and even, fine and close, smooth, outward appearance is good.

Will through the magnesium alloy (Mg alloy surface has anode oxide film) of above-mentioned surface-treated with in 3.5% sodium chloride solution, do the Tafel polarization curve without anodised magnesium alloy and carry out corrosion evaluation, see Fig. 1.A represents without anodised magnesium alloy sample among the figure; B represents the anodic oxidation of magnetism alloy sample after the inventive method is handled.A corrosion potential E_Corr=-1.343V, B corrosion potential E_Corr=-1.589V, the A corrosion potential has improved 246mV than B; A corrosion current I_Corr=2.028 * 10^-8A/cm², B corrosion current I_Corr=3.206 * 10^-5A/cm², contrast corrosion electric current density A has reduced by three orders of magnitude than B; The film voltage breakdown of A is brought up to-1.144V.As seen, the AZ31 corrosion resistance of magnesium alloy after the anodic oxidation of optimization technology can obtain very big raising.With reference to State Standard of the People's Republic of China GB/T 10125-1997, " artificial atmosphere corrosion test-salt-fog test " carries out, grade with reference to State Standard of the People's Republic of China GB/T 6461-2002 " metal and the sample of other inorganic covers after corrosion test and the grading of test specimen on the metallic matrix " standard, after salt-fog test is carried out 8 hours, discovery is corroded fully without anodised magnesium alloy sample, and rank only is 1 grade; Mg alloy surface after the method for the invention is handled does not change; Intermittently sprayed salt fog 96 hours, place spot corrosion just appears in Mg alloy surface, is decided to be 8 grades according to the grading standard, and erosion resistance is good.

Example 4:

Electrolytic solution:

NaOH：45g/L

Na₂SiO₃：80g/L

PASP：40ml/L

Trisodium Citrate: 5g/L

Magnesium alloy materials: the bar-shaped sample of AZ31 magnesium alloy

With the pre-treatment of holing behind the magnesium alloy sample, polishing, tap water are cleaned, distilled water cleans, acetone is ultrasonic, distilled water cleans, dries up.

Magnesium alloy sample anodic oxidation in above-mentioned electrolytic solution, anodic oxidation condition: direct supply, constant current mode, adopting water-bath mode controlled temperature scope on the rocks is 10-30 ℃, and anodizing time is 10-30min, and current density is 1-20mA/cm²Whole anode oxidation process carries out under agitation condition.

Film forming result: be canescence through anodised AZ31 magnesium alloy outward appearance, overlay film is complete good, fine and close, smooth, even.Will through the magnesium alloy (Mg alloy surface has anode oxide film) of above-mentioned surface-treated with in 3.5% sodium chloride solution, do the Tafel polarization curve without anodised magnesium alloy and carry out corrosion evaluation, corrosion potential through anodised magnesium alloy rod AZ31 is-1.353V that corrosion electric current density is 1.874e^-7A/cm², and be-1.525V that corrosion electric current density is 5.141e without the corrosion potential of anodised bar magnesium alloy^-6A/cm², obviously as seen obviously improve through anodised magnesium alloy corrosive nature.

Example 5:

According to table 4 preparation electrolytic solution of the present invention, adopt the inventive method to handle the surface of magnesium alloy, have effect of the present invention equally.

Table 4 electrolyte prescription table

Annotate: except that the PASP concentration unit was ml/L, other concentration of component unit was g/L in the table 4.

Though the present invention discloses as above with preferred embodiment; right its is not in order to limit the present invention; any person of ordinary skill in the field; without departing from the spirit and scope of the present invention; when can doing a little change and improvement, so protection scope of the present invention is as the criterion when looking the claim person of defining.

Claims (8)

1. the electrolytic solution of an anodic oxidation of magnetism alloy, it is characterized in that consisting of of described electrolytic solution: poly aspartic acid 20-60ml/L, water glass or potassium silicate 40-100g/L, sodium hydroxide or potassium hydroxide 15-60g/L, additive is any one in phytic acid, phytate, citric acid, Citrate trianion, oxalic acid, the oxalate, wherein, phytic acid or phytate concentration are 3-15g/L, citric acid or citric acid salt concentration are 5-20g/L, oxalic acid or concentration of oxalate are 5-20g/L, and the pH of described electrolytic solution is 10-13.

2. the electrolytic solution of anodic oxidation of magnetism alloy according to claim 1, it is characterized in that consisting of of described electrolytic solution: poly aspartic acid 40ml/L, water glass or potassium silicate 60-80g/L, sodium hydroxide or potassium hydroxide 30-45g/L, additive is any one in phytic acid, phytate, citric acid, Citrate trianion, oxalic acid, the oxalate, wherein, phytic acid or phytate concentration are 3-15g/L, citric acid or citric acid salt concentration are 5-20g/L, oxalic acid or concentration of oxalate are 5-20g/L, and the pH of described electrolytic solution is 10-13.

3. the electrolytic solution of anodic oxidation of magnetism alloy according to claim 1 and 2, it is characterized in that: described phytate is the basic metal phytate, described basic metal phytate is sodium phytate or POTASSIUM PHYTATE.

4. the electrolytic solution of anodic oxidation of magnetism alloy according to claim 1, it is characterized in that: described Citrate trianion is an alkali metal citrate, described an alkali metal salt is Trisodium Citrate or Tripotassium Citrate.

5. the electrolytic solution of anodic oxidation of magnetism alloy according to claim 1 and 2, it is characterized in that: described oxalate is the basic metal oxalate, described basic metal oxalate is sodium oxalate or potassium oxalate.

6. adopt the method for the electrolytic solution processing magnesium alloy of claim 1 or 2 described anodic oxidation of magnetism alloy, it is characterized in that following steps are arranged:

A. magnesium alloy pre-treatment;

B. anodic oxidation of magnetism alloy: with stainless steel is negative electrode, and magnesium alloy is an anode, under the agitation condition, and constant voltage direct current, current density 10～30mA/cm², temperature is 10～35 ℃, the time is 10～30min.

7. method according to claim 6 is characterized in that: anodic oxidation of magnetism alloy adopts water-bath mode controlled temperature on the rocks.

8. method according to claim 6 is characterized in that the magnesium alloy pre-treatment is: boring, polishing, water clean, distilled water cleans, acetone is ultrasonic, distilled water cleans, dries up.

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