CN110629268A

CN110629268A - Surface protection process for high-precision light alloy part

Info

Publication number: CN110629268A
Application number: CN201911037915.9A
Authority: CN
Inventors: 刘永青; 肖宏超; 程锐; 黄硕; 洪志刚
Original assignee: Changsha New Material Industry Research Institute Co Ltd
Current assignee: Changsha New Material Industry Research Institute Co Ltd
Priority date: 2019-10-29
Filing date: 2019-10-29
Publication date: 2019-12-31

Abstract

The invention discloses a surface protection process for a high-precision light alloy part, which comprises three steps of pretreatment, electrochemical oxidation, coating and post-processing in sequence. According to the surface protection process provided by the invention, the oxide film and the ceramic layer are sequentially formed on the surface of the part through electrochemical oxidation and coating, so that the comprehensive protection capability is improved, and the ceramic layer is uniform in texture and easy to machine subsequently; and then processing is carried out to ensure the processing precision, thereby realizing the purpose of ensuring the precision of parts while solving the problem of surface protection of the high-precision light alloy.

Description

Surface protection process for high-precision light alloy part

Technical Field

The invention relates to the technical field of surface protection of high-precision light alloy parts, in particular to a surface protection process for high-precision light alloy parts.

Background

The light alloy of magnesium, aluminum, titanium and the like is widely applied to the fields of aerospace, automobiles, 3C and the like due to small density. But because of poor self corrosion resistance and wear resistance, the surface protection is indispensable, in particular to magnesium alloy which is the lightest metal structure material in practical application at present, and the density of pure magnesium is 1.74g/cm³2/3 of aluminum alloy, 2/5 of titanium alloy and 1/4 of steel are equivalent to most engineering plastics. But the standard potential of magnesium is very negative (-2.37V), and the magnesium has extremely high chemical and electrochemical activity; in addition, the oxide film of the magnesium alloy is loose and porous (the density ratio of MgO to Mg is 0.81), and pitting corrosion is easy to occur; in addition, secondary phases or impurities inside the alloy are liable to cause galvanic corrosion. Therefore, the corrosion resistance of the magnesium alloy is extremely low, and the corrosion resistance is a main factor for restricting the wide application of the magnesium alloy.

At present, the common protection technologies for light alloys include chemical conversion, micro-arc oxidation, chemical plating or electroplating, organic spraying, and the like. The protective capability of chemical conversion is limited, and the chemical conversion is generally only used for intermediate transfer protection or coating pretreatment. The micro-arc oxidation technology has been applied to magnesium alloy structural parts such as car engine shells, hubs, submachine gun stocks, hot water exchange tubes and the like. Research results show that the comprehensive performance is obviously improved after micro-arc oxidation treatment, the corrosion current density is reduced by about 2-4 orders of magnitude, the wear rate is reduced by more than 80%, but in the protection process of actual complex parts of engineering, the thickness is not uniform due to the fact that structural parts are special, electric field lines are not uniformly distributed, the local current density difference of the parts causes the thickness to be not uniform, the integral corrosion resistance cannot reach the result, and therefore salt spray verification cannot reach more than 96h, especially at threaded holes. The chemical plating or electroplating protection corrosion resistance is not enough, in addition, the thickness of the electrogalvanizing is about 5-15 μm, the hot galvanizing is generally more than 65 μm and even up to 100 μm, which shows that the size of the electrogalvanizing is generally increased by 0.01mm after the mechanical galvanizing, and in the actual application, the final tolerance is the tolerance of the machining plus the tolerance of the coating protection, so the batch production is carried out, and the rejection rate is greatly improved. The same organic spraying technology has excellent corrosion resistance, the salt spray sample reaches more than 1000h, but the precision of the finish machining surface after protection is insufficient.

In view of the current state of the surface protection technology, a single technology cannot meet the requirements of high precision, corrosion resistance and the like at the same time, so that the combination of multiple technologies is a development trend of light alloy surface protection in the future. Firstly, the corrosion resistance protection of the light alloy parts is the precondition of application. Secondly, the light alloy part replaces steel, copper and the like to be used for relative motion parts, and the coating is required to be large in thickness and high in hardness when being applied to a high-load anti-wear environment; the coating is applied to a low-load precise antifriction environment, and high compactness, low roughness and low friction factor are required. Therefore, ensuring the precision of the part while solving the problem of light alloy surface protection is a technological bottleneck which needs to be solved urgently in practical engineering application.

Disclosure of Invention

The invention provides a surface protection process for a high-precision light alloy part, which is used for overcoming the defects that the surface protection of the high-precision light alloy part, the precision guarantee of the part and the like cannot be simultaneously considered in the prior art, and the precision guarantee of the part is realized while the surface protection of the high-precision light alloy part is solved.

In order to achieve the purpose, the invention provides a surface protection process for a high-precision light alloy part, which comprises the following steps:

s1: pretreating the surface of a light alloy part to be subjected to surface protection;

s2: carrying out electrochemical oxidation and coating on the light alloy part subjected to S1 in sequence to obtain a light alloy part with an oxide film and a ceramic layer on the surface;

s3: carrying out post-processing treatment on the light alloy part subjected to S2 to obtain the high-precision light alloy part;

the thickness of the oxide film is 5-20 mu m; the thickness of the ceramic layer is 30-100 mu m; the coating material is oily ceramic paint.

Compared with the prior art, the invention has the beneficial effects that:

1. the surface protection process for the high-precision light alloy part, provided by the invention, comprises the following steps of firstly pretreating the surface of the light alloy part to be subjected to surface protection so as to thoroughly remove oil stains and dirt on the surface of the part, ensure the uniformity of the surface of the part, improve the binding force between an oxidation film and the surface of the part and provide the quality of a final product; then, a light alloy part with an oxide film and a ceramic layer on the surface is obtained through electrochemical oxidation and coating, the electrochemical oxidation has no selectivity on the material of the part to be processed, the light alloy part is suitable for various materials, meanwhile, the bonding force between the oxide film and the surface of the part is excellent in a growth mode of the electrochemical oxidation, and the influence on the plane precision of the part is very small (the change before and after treatment is only 1-3 mu m); the single oxide film can not well meet the service performance requirement of the part under the severe condition, so the part after electrochemical oxidation is further treated by adopting a coating treatment mode, the comprehensive protection capability is improved, and the ceramic layer has uniform texture and is easy to machine subsequently; in addition, the thickness of the oxide layer is controlled to be 5-20 microns, the thickness of the ceramic layer is controlled to be 30-100 microns, and the thickness of the oxide layer is controlled, so that firstly, the proper thickness of the oxide layer plays a role in supporting the whole coating, the hardness of the oxide layer is influenced by the thinness of the oxide layer, and the corrosion resistance requirement cannot be met; the excessive thickness affects the binding force and compactness of the ceramic layer, because the pore size of the micropores on the surface of the oxide film layer is in positive correlation with the thickness of the oxide film, and the pore size of the micropores on the surface of the oxide film can directly affect the binding force and compactness of the ceramic layer (the oxide film has large pore size and high porosity, so that the ceramic layer has very good absorption effect and the finally formed ceramic layer is firmly combined with the oxide film); the thickness of the ceramic layer is controlled to be 30-100 mu m, and the ceramic layer is not easy to machine due to too thin thickness, and the ceramic layer is poor in compactness due to too thick thickness; in addition, the simple coating treatment cannot meet the use requirement of high-precision parts, so the coating is subjected to finish machining by adopting a post-processing treatment mode after coating, but the processing has a requirement on coating materials, the post-processing can not be carried out on any coating, and certain hardness and adhesive force need to be ensured, so the coating is carried out by selecting the oily ceramic paint with excellent hardness and adhesive force, firstly, the hardness of the coating can reach more than 6H (the average of common polyurethane and Teflon is 2-3H), and secondly, the adhesive force of the ceramic layer on an oxide layer is good. In conclusion, the invention realizes the protection of the surface of the high-precision light alloy and ensures the precision of parts by electrochemical oxidation and coating and by selecting the coating material and controlling the thickness of the oxide film and the ceramic layer.

2. The high-precision light alloy part salt spray obtained by the surface protection process for the high-precision light alloy part provided by the invention has 1000h, the grade reaches 9, the wear resistance is improved by more than three times compared with the existing wear resistance, the friction coefficient is reduced by one time, and good antifriction and wear resistance effects are realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a flow chart of the surface protection process for high-precision light alloy parts provided by the invention;

FIG. 2 is a schematic view showing in-situ growth of an oxide film layer in the case of micro-arc oxidation in example 1;

FIG. 3 is a schematic diagram illustrating the in-situ growth of an oxide film layer during anodic oxidation in example 2.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.

The drugs/reagents used are all commercially available without specific mention.

The invention provides a surface protection process for a high-precision light alloy part, which comprises the following steps as shown in figure 1:

preferably, the pretreatment includes degreasing treatment, activation treatment, and surface conditioning. The oil removal treatment is carried out to remove oil stains and dirt on the surface of the part and ensure the uniformity of the surface of the part; the surface oxide is removed by the activation treatment, so that the subsequent electrochemical oxidation process can be smoothly carried out; surface conditioning treatment is carried out to remove loose oxides on the surface of the workpiece after activation, so that the surface of the workpiece is shiny and clean.

Preferably, the deoiling liquid for deoiling treatment is one of a deoiling liquid I and a deoiling liquid II;

deoiling liquid I: 50g/L of sodium hydroxide, 4g/L of sodium phosphate, 6g/L of sodium carbonate and 2mg/L of sodium dodecyl sulfate;

and (3) deoiling liquid II: 50g/L of sodium hydroxide, 4g/L of sodium phosphate and 6g/L of sodium carbonate; and proper deoiling liquid is selected, so that the deoiling effect is good, and no residue is left on the surface of the part.

The activating solution for activating treatment is one of an activating solution I and an activating solution II;

activating solution I: 8g/L of trisodium phosphate, 3g/L of ammonium sulfate, 6g/L of sodium nitrate, 15g/L of tartaric acid and 8g/L of oxalic acid;

and (3) activating solution II: 60g/L of sodium hydroxide;

the surface conditioning liquid of the surface conditioning is one of a surface conditioning liquid I and a surface conditioning liquid II;

liquid I is prepared: 10g/L of sodium tripolyphosphate, 20g/L of sodium hydroxide, 5ml/L of triethanolamine and 6ml/L of triton;

and (3) surface conditioning liquid II: 50% of nitric acid.

Preferably, the temperature of the oil removing treatment is 60 ℃, and the time is 4 min;

the temperature and time conditions of the activation treatment include:

when the activating solution I is adopted, the temperature is 45 ℃ and the time is 1 min;

when the activating solution II is adopted, the temperature is room temperature, and the time is 1 min;

the temperature and time conditions of the schedules include:

when the surface conditioning liquid I is adopted, the temperature is 80 ℃, and the time is 5 min;

when the surfactant solution II is used, the temperature is room temperature and the time is 20 s. The pretreatment conditions are selected according to different reagents to realize pretreatment with better effect.

the thickness of the oxide film is 5-20 mu m; the thickness of the ceramic layer is 30-100 mu m; the coating material is oily ceramic paint;

preferably, the electrochemical oxidation is one of anodic oxidation, hard anodic oxidation and micro-arc oxidation. The reason for selecting the anodic oxidation, the hard anodic oxidation or the micro-arc oxidation to carry out surface priming treatment on the part is as follows: anodic oxidation, hard anodic oxidation or micro-arc oxidation have no selectivity on the material of the part, and are suitable for parts made of various materials; secondly, the oxide film has good corrosion resistance and wear resistance and can support the ceramic layer; the growing mode of anodic oxidation, hard anodic oxidation or micro-arc oxidation treatment enables the bonding force between the oxide film and the surface of the part to be excellent; meanwhile, the surface of the oxide film has a porous structure, so that the specific surface area of the whole part is increased, and the bonding force between the oxide film and the ceramic layer is increased; and fourthly, the anodic oxidation, the hard anodic oxidation or the micro-arc oxidation all belong to in-situ growth, the influence on the plane precision of the part is very small, and the change before and after the treatment is only 1-3 mu m. Therefore, the electrochemical oxidation process can effectively improve the corrosion resistance and the wear resistance of the part and can ensure the precision of the plane of the part to a certain degree.

Preferably, the anodic oxidation electrolyte is: 200g/L of sulfuric acid;

the electrolyte for hard anodic oxidation is as follows: 12% H₂SO₄0.02-0.05 mol/L2-aminoethylsulfonic acid;

the micro-arc oxidation electrolyte comprises: 12g/L of sodium silicate, 9g/L of potassium hydroxide, 5mL/L of triethanolamine, 3g/L of EDTA-disodium, 12g/L of potassium fluoride and 12 of PH.

Preferably, the coating method adopts a spraying technology; the common spraying technology is adopted, so that the cost is low and the effect is good.

Preferably, the coating is specifically:

deoiling by adopting deoiling liquid I;

baking for the first time at 130-150 ℃ for 20-40 min;

spraying for the first time, wherein the voltage is 50-70 KV, the distance between a spray gun and a workpiece is 280mm, and the powder spraying amount is 60-100 g/min and is 2-5 min;

baking for the second time at 140-160 ℃ for 40-50 min;

spraying for the second time, wherein the voltage is 65-100 KV, the distance between a spray gun and the workpiece is 300mm, and the powder spraying amount is 80-160 g/min and 4-8 min;

and (3) baking for the third time at 220-250 ℃ for 40-60 min. The coating process of spraying and baking for multiple times is adopted, so that the ceramic layer obtained by coating is uniform and flat, can be well combined on the oxide film, and the thickness of the ceramic layer can be accurately controlled.

preferably, the post-processing treatment is one of milling, grinding and laser etching. The plane precision of the coated part cannot be guaranteed, and the assembly of key surfaces with precision requirements cannot be met, so that the invention provides a solution for the problem, namely, a mode of post-processing a coating is adopted to solve the problem of insufficient precision after coating. The post-processing of the invention processes the coating by milling, grinding or laser etching, etc., the milling and grinding can ensure the plane precision of the key surface, and the laser etching etches the plane coating by the difference of the high and low focal lengths of the small planes and the difference of the actual power, thereby improving the plane precision.

Preferably, the light alloy is a valve metal and alloys thereof.

Preferably, the light alloy is one of a magnesium alloy, an aluminum alloy, and a titanium alloy. The light alloy has poor self corrosion resistance and wear resistance and is essential for surface protection.

Example 1

The embodiment provides a surface protection process for a high-precision light alloy part, which comprises the following steps:

step 1, deoiling the surface of AZ31 magnesium alloy, wherein the deoiling liquid is as follows: 50g/L of sodium hydroxide, 4g/L of sodium phosphate, 6g/L of sodium carbonate and 2mg/L of sodium dodecyl sulfate. The oil removal temperature is 60 ℃ and the time is 4 min. After the treatment, the water drops on the surface of the part are continued for 10s without interruption.

Step 2, activating, wherein the activating solution is as follows: 8g/L trisodium phosphate, 3g/L ammonium sulfate, 6g/L sodium nitrate, 15g/L tartaric acid and 8g/L oxalic acid. The temperature is 45 deg.C, and the time is 1 min. And no pockmark exists on the surface of the part after the activation is finished.

And step 3, surface adjustment, wherein the surface adjustment solution is as follows: 10g/L of sodium tripolyphosphate, 20g/L of sodium hydroxide, 5ml/L of triethanolamine and 6ml/L of triton. The temperature is 80 deg.C, and the time is 5 min. After the surface adjustment is finished, the surface of the part is shiny, and no residual loose oxide exists.

Step 4, micro-arc oxidation surface treatment, wherein the electrolyte comprises the following components: 12g/L of sodium silicate, 9g/L of potassium hydroxide, 5mL/L of triethanolamine, 3g/L of EDTA-disodium (ethylene diamine tetraacetic acid), 12g/L of potassium fluoride and 12 of PH. The positive pulse voltage and the negative pulse voltage are 380/60V respectively, the frequency is 800Hz/800Hz, the duty ratio is 10%/10%, and the ratio of the stages is 1: 1. The time is 10 min. The thickness of the oxide film obtained was 12 μm. FIG. 2 is a schematic diagram showing the in-situ growth of an oxide film layer during micro-arc oxidation, wherein the micro-arc oxide film layer is grown in situ, that is, the micro-arc oxide film layer is grown simultaneously inward and outward with the substrate interface as a base surface.

And 5, drying, namely drying the parts at the temperature of 100 ℃ for 20 min.

And 6, spraying treatment, which comprises the following specific steps: removing oil, wherein the oil removing solution is as follows: 50g/L of sodium hydroxide, 4g/L of sodium phosphate and 6g/L of sodium carbonate. The oil removal temperature is 60 ℃ and the time is 6 min. After the treatment is finished, the water drops on the surface of the part are continuously continued for 10S without interruption. Secondly, baking for the first time at 150 ℃ for 30 min; thirdly, spraying for the first time, wherein the voltage is 70KV, the distance between a spray gun and the workpiece is 280mm, and the powder spraying amount is 100g/min and 5 min; baking for the second time at 150 ℃ for 40 min; spraying for the second time, wherein the voltage is 100KV, the distance between a spray gun and the workpiece is 300mm, and the powder spraying amount is 160g/min and 8 min; sixthly, baking for the third time at the temperature of 240 ℃ for 60 min. A ceramic layer having a thickness of 80 μm was formed.

And 7, milling finish coating of the part to obtain the high-precision light alloy part.

And 8, measuring the planeness of the finish machining surface of the obtained high-precision light alloy part.

And 9, performing salt spray performance (standard reference GJB 150.11A-2009) and friction wear test on the obtained high-precision magnesium alloy part.

Example 2

step 1, deoiling the surface of 6061 aluminum alloy, wherein the deoiling liquid is as follows: 50g/L of sodium hydroxide, 4g/L of sodium phosphate and 6g/L of sodium carbonate. The oil removal temperature is 60 ℃ and the time is 4 min. After the treatment, the water drops on the surface of the part are continued for 10s without interruption.

Step 2, activating, wherein the activating solution is as follows: 60g/L of sodium hydroxide. At room temperature, for 1 min. And no pockmark exists on the surface of the part after the activation is finished.

And step 3, surface adjustment, wherein the surface adjustment solution is as follows: 50% of nitric acid. At room temperature, time 20 s. After the surface adjustment is finished, the surface of the part is shiny, and no residual loose oxide exists.

Step 4, anodizing, wherein the electrolyte is: sulfuric acid 200 g/L. The time is 30 min. The thickness of the oxide film obtained was 20 μm. FIG. 3 is a schematic diagram of in-situ growth of an oxide film layer during anodization, wherein the anodized film layer grows inward on the basis of a substrate interface and has little influence on the precision of a workpiece.

And 6, spraying treatment, which comprises the following specific steps: removing oil, wherein the oil removing solution is as follows: 50g/L of sodium hydroxide, 4g/L of sodium phosphate, 6g/L of sodium carbonate and 2mg/L of sodium dodecyl sulfate. The oil removal temperature is 60 ℃ and the time is 6 min. After the treatment is finished, the water drops on the surface of the part are continuously continued for 10S without interruption. Secondly, baking for the first time at 130 ℃ for 30 min; thirdly, spraying for the first time, wherein the voltage is 50KV, the distance between a spray gun and the workpiece is 280mm, and the powder spraying amount is 60g/min and 2 min; baking for the second time at 140 ℃ for 40 min; spraying for the second time, wherein the voltage is 65KV, the distance between a spray gun and the workpiece is 300mm, and the powder spraying amount is 80g/min and 4 min; sixthly, baking for the third time at the temperature of 240 ℃ for 40 min. A ceramic layer having a thickness of 30 μm was formed.

And 7, grinding the finish machining surface coating of the part to obtain the high-precision light alloy part.

Example 3

Step (ii) of4, hard anodizing surface treatment, wherein the electrolyte comprises the following components: 12% H₂SO₄0.02-0.05 mol/L2-aminoethylsulfonic acid. The current density is 4A/dm²The temperature is 2 ℃, the time is 10min, and the thickness of the obtained oxide film is 5 mu m.

And 5, drying, namely drying the parts at the temperature of 100 ℃ for 10 min.

And 6, spraying treatment, which comprises the following specific steps: removing oil, wherein the oil removing solution is as follows: 50g/L of sodium hydroxide, 4g/L of sodium phosphate and 6g/L of sodium carbonate. The oil removal temperature is 60 ℃ and the time is 6 min. After the treatment is finished, the water drops on the surface of the part are continuously continued for 10S without interruption. Secondly, baking for the first time at 150 ℃ for 30 min; thirdly, spraying for the first time, wherein the voltage is 70KV, the distance between a spray gun and the workpiece is 280mm, and the powder spraying amount is 100g/min and 5 min; baking for the second time at 150 ℃ for 40 min; spraying for the second time, wherein the voltage is 100KV, the distance between a spray gun and the workpiece is 300mm, and the powder spraying amount is 160g/min and 8 min; sixthly, baking for the third time at the temperature of 240 ℃ for 60 min. A ceramic layer having a thickness of 100 μm was formed.

And 7, carrying out laser etching processing on the finish-processed surface coating of the part to obtain the high-precision light alloy part.

Example 4

The surface protection process for the light alloy part comprises the following steps:

Step 4, micro-arc oxidation surface treatment, wherein the electrolyte comprises the following components: 12g/L of sodium silicate, 9g/L of potassium hydroxide, 5mL/L of triethanolamine, 3g/L of EDTA-disodium (ethylene diamine tetraacetic acid), 12g/L of potassium fluoride and 12 of PH. The positive pulse voltage and the negative pulse voltage are 380/60V respectively, the frequency is 800Hz/800Hz, the duty ratio is 10%/10%, and the ratio of the stages is 1: 1. The time is 10 min. The thickness of the oxide film obtained was 5 μm.

Step 6, spraying treatment, namely adopting common polyurethane and Teflon coating, and specifically comprising the following steps: removing oil, wherein the oil removing solution is as follows: 50g/L of sodium hydroxide, 4g/L of sodium phosphate and 6g/L of sodium carbonate. The oil removal temperature is 60 ℃ and the time is 6 min. After the treatment is finished, the water drops on the surface of the part are continuously continued for 10S without interruption. Secondly, baking for the first time at 150 ℃ for 30 min; thirdly, spraying for the first time, wherein the voltage is 70KV, the distance between a spray gun and the workpiece is 280mm, and the powder spraying amount is 100g/min and 5 min; baking for the second time at 150 ℃ for 40 min; spraying for the second time, wherein the voltage is 100KV, the distance between a spray gun and the workpiece is 300mm, and the powder spraying amount is 160g/min and 8 min; sixthly, baking for the third time at the temperature of 240 ℃ for 60 min. A ceramic layer having a thickness of 100 μm was formed.

And 7, milling the finish machining surface coating of the part.

Experimental results show that when the coating is milled, a large-area cutter adhesion problem and an uneven surface occur, because the hardness of the coating is not enough, the average hardness is only 2-3H. Not all coatings can meet the post-treatment processing requirements.

Table 1 shows the results of flatness measurements of the finished surfaces of the high-precision light alloy parts obtained in examples 1 to 3. The test result shows that the flatness tolerance value of the finished surface of the part is increased from 5 grades to about 9 grades through electrochemical oxidation/coating composite treatment, the flatness tolerance value is reduced to below 7 grades after post-processing, and the plane precision is obviously improved. The process can effectively improve the surface protection effect of the part and meet the requirement of high plane precision. (for rating reference GB/T1184-1996).

Table 2 shows the salt spray test and the friction and wear results of the high-precision light alloy part obtained in example 1, and it can be seen from the table that the salt spray of the high-precision light alloy part obtained by the surface protection process for the high-precision light alloy part provided in this embodiment is rated as 9-grade corrosion for 1000 hours, the wear resistance is improved by more than three times compared with the existing one, and the friction coefficient is reduced by one time, so that a good friction and wear resistance effect is achieved.

TABLE 1 results of flatness measurement of finished surface of high-precision light alloy parts obtained in examples 1 to 3

Table 2 salt spray test and frictional wear results of the high-precision light alloy parts obtained in example 1

Test specimen	Salt spray results	Coefficient of friction	Loss on abrasion (%)
				AZ31	Filiform corrosion occurs in 24h	0.225	0.326
Example 1	1000h, perfect surface and grade 9	0.102	0.014

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. A surface protection process for high-precision light alloy parts is characterized by comprising the following steps:

2. The surface protection process for a high-precision light alloy part according to claim 1, wherein the light alloy is a valve metal and an alloy thereof.

3. The surface protection process for a high-precision light alloy part according to claim 2, wherein the light alloy is one of a magnesium alloy, an aluminum alloy and a titanium alloy.

4. The surface protection process for a high-precision light alloy part according to claim 1, wherein in the step S1, the pretreatment includes degreasing treatment, activation treatment and surface conditioning.

5. The surface protection process for the high-precision light alloy part as claimed in claim 4, wherein the deoiling liquid for the deoiling treatment is one of a deoiling liquid I and a deoiling liquid II;

and (3) deoiling liquid II: 50g/L of sodium hydroxide, 4g/L of sodium phosphate and 6g/L of sodium carbonate;

and (3) activating solution II: 60g/L of sodium hydroxide;

and (3) surface conditioning liquid II: 50% of nitric acid.

6. The surface protection process for a high-precision light alloy part according to claim 4 or 5, wherein the temperature of the degreasing treatment is 60 ℃ and the time is 4 min;

the temperature and time conditions of the activation treatment include:

the temperature and time conditions of the schedules include:

when the surfactant solution II is used, the temperature is room temperature and the time is 20 s.

7. The surface protection process for high-precision light alloy parts according to claim 1, wherein in the step S2, the electrochemical oxidation is one of anodic oxidation, hard anodic oxidation and micro-arc oxidation.

8. The surface protection process for a high-precision light alloy part according to claim 7, wherein the anodizing electrolyte is: 200g/L of sulfuric acid;

9. The surface protection process for a high-precision light alloy part according to claim 1, wherein in the step S2, the coating is specifically:

deoiling by adopting deoiling liquid I;

baking for the first time at 130-150 ℃ for 20-40 min;

baking for the second time at 140-160 ℃ for 40-50 min;

and (3) baking for the third time at 220-250 ℃ for 40-60 min.

10. The surface protecting process for a high-precision light alloy part according to claim 1, wherein in the step S3, the post-processing treatment is one of milling, grinding and laser etching.