CN102409371B - Method for detecting micro-arc oxidation arcing characteristics of alloy by using anodic polarization curve - Google Patents

Abstract

The invention relates to a method for detecting arc-starting characteristics of alloy micro-arc oxidation by using anodic polarization curve, and the invention relates to a method for alloy micro-arc oxidation. The present invention aims to solve the technical problems of large workload, waste of electric energy and solution raw materials caused by the existing method of using the micro-arc oxidation experiment process to verify the influence of the type and amount of additives in the electrolyte on the arc-starting characteristics of the micro-arc oxidation. The method of the present invention: measure the anodic polarization curve of the alloy in the electrolytic solution to be verified with the voltage U as the abscissa and the current I as the ordinate, and whether there is a passivation zone to determine whether micro-arc oxidation can be carried out to passivate The width of the passivation interval determines the voltage level of the micro-arc oxidation arc discharge of the alloy in the electrolyte. When the width of the passivation interval is similar, the value of the polarization current before the passivation film layer becomes unstable determines the micro-arc of the alloy in the electrolyte. Oxidation arc discharge voltage is high or low; the method of the present invention is a low-voltage, low-current-density process, which saves energy. It can be used to predict the arc starting characteristics of alloy micro-arc oxidation.

Description

The Method of Using Anode Polarization Curve to Detect the Arcing Characteristics of Alloy Micro-arc Oxidation

technical field

The invention relates to a method for alloy micro-arc oxidation.

Background technique

Magnesium alloys are used in industrial fields such as aviation, automobiles and electronic communications due to their advantages such as low density, high specific strength and specific stiffness, and good electromagnetic shielding. However, due to the active chemical properties of magnesium, it is very easy to oxidize, and a loose and porous oxide film is formed on the surface. The oxide film has poor protection ability for the substrate and is not suitable for use in most corrosive environments. Applications. Micro-arc oxidation is a surface modification technology developed on the basis of anodic oxidation. This technology is to place metals such as magnesium, aluminum, titanium or their alloys in the electrolyte, under high temperature and high pressure, thermochemistry, plasma chemistry and The method of generating spark discharge on the surface of the material to form a ceramic film layer under the combined action of electrochemistry and the like. This technology has the characteristics of simple process, less environmental pollution and high efficiency, and the micro-arc oxidation ceramic film has the advantages of strong film-base binding force, wear resistance, corrosion resistance, high temperature oxidation resistance and good insulation, so the use of micro-arc oxidation Surface modification of magnesium alloys is promising.

Because micro-arc oxidation is a high-voltage, high-current-density working process, in actual production, when the one-time treatment area is large, there will be problems such as high requirements for the power supply of micro-arc oxidation or the rated power of the grid, and low energy utilization. The electrolyte formula is one of the important factors affecting the micro-arc oxidation reaction. Appropriate electrolyte additives have a significant effect on reducing the working voltage of the micro-arc oxidation and thus reducing the power required for the micro-arc oxidation process. Which kind of additive electrolyte can carry out micro-arc oxidation discharge, and which additive is beneficial to reduce the voltage of micro-arc oxidation discharge, must be verified by high-voltage, high-current-density micro-arc oxidation experimental process, which makes the workload huge, and A large amount of electric energy and solution raw materials are wasted.

Contents of the invention

The present invention aims to solve the technical problems of large workload, waste of electric energy and solution raw materials caused by the existing method of using the micro-arc oxidation experiment process to verify the influence of the type and amount of additives in the electrolyte on the arc-starting characteristics of the micro-arc oxidation. And it provides a method for detecting arcing characteristics of alloy micro-arc oxidation by using anodic polarization curve.

The method of utilizing the anodic polarization curve of the present invention to detect the arcing characteristics of alloy micro-arc oxidation is carried out according to the following steps:

1. Prepare the electrolyte to be verified;

Two, measure the anodic polarization curve with the voltage U as the abscissa and the current I as the ordinate in the electrolytic solution to be verified obtained in step 1;

3. On the anodic polarization curve measured in step 2, if there is no passivation zone, the alloy cannot undergo micro-arc oxidation in the electrolyte; if there is a passivation zone, the alloy can undergo micro-arc oxidation in the electrolyte Arc oxidation; the wider the passivation interval, the lower the voltage of the alloy in the electrolyte for micro-arc oxidation arc discharge; when the passivation interval is similar, the polarization current on the anodic polarization curve before the passivation film becomes unstable The smaller the value, the lower the arc discharge voltage of the alloy in the electrolyte, and thus the arc start characteristics of the alloy are obtained.

The present invention adopts the anode polarization curve of the voltage-current format to determine whether the magnesium alloy can be subjected to micro-arc oxidation discharge in the electrolyte and the high and low order of the micro-arc oxidation discharge voltage in different electrolytes, and uses the corresponding electrolyte as the magnesium alloy The working solution in the electrochemical polarization behavior, through the anodic polarization curve, judge whether the magnesium alloy can perform micro-arc oxidation discharge in the electrolyte and the level of arc starting voltage when performing micro-arc oxidation discharge in different electrolytes , to provide a simple and effective reference method for the selection of additives in micro-arc oxidation electrolyte. On the anodic polarization curve, if there is no passivation zone, that is, the alloy cannot passivate in the electrolyte, the alloy cannot perform micro-arc oxidation discharge behavior in the electrolyte; on the anodic polarization curve, if There is a passivation zone, that is, the alloy can undergo passivation in the electrolyte, and the alloy can perform micro-arc oxidation discharge behavior in the electrolyte; the determination of the arc-starting voltage of the micro-arc oxidation is carried out in two steps: first, the alloy is in The level of arcing voltage in different electrolytes is judged by the passivation interval of the anodic polarization curve in the corresponding electrolyte. On the anodic polarization curve, the wider the passivation interval, the lower the alloy micro-arc oxidation arc discharge voltage in the corresponding electrolyte; When the width of the upper passivation interval is similar, the level of the arcing voltage can be judged by the magnitude of the polarization current before the passivation film is unstable on the anodic polarization curve. On the anodic polarization curve, the smaller the polarization current before the passivation film becomes unstable, the lower the arc discharge voltage of alloy micro-arc oxidation in the corresponding electrolyte. Compared with the micro-arc oxidation, the condition for testing the alloy anodic polarization curve in the method of the invention is a low-voltage, low-current-density process, thereby simplifying the process of judging the characteristics of the alloy micro-arc oxidation, thereby saving energy.

The invention can be used to predict the arc starting characteristics of alloy micro-arc oxidation.

Description of drawings

Fig. 1 is the anodic polarization curve that records in the step 2 of test one, and wherein a is the anodic polarization curve that the first kind is the AZ31 magnesium alloy in the sodium silicate aqueous solution of 10g/L for concentration, and b is that the second kind is Concentration is the anodic polarization curve of AZ31 magnesium alloy in sodium phosphate aqueous solution of 10g/L; c is the third kind is the anodic polarization curve of AZ31 magnesium alloy in potassium chloride aqueous solution with concentration of 10g/L; d is the fourth kind Concentration is the anodic polarization curve of AZ31 magnesium alloy in 10g/L sodium molybdate aqueous solution; e is the anodic polarization curve of AZ31 magnesium alloy in the sodium dihydrogen phosphate aqueous solution that concentration is 10g/L for the fifth;

Fig. 2 is the anodic polarization curve that records in the step 2 of test two; Wherein f is the anodic polarization curve of AZ31 magnesium alloy in the sodium silicate aqueous solution that concentration is 10g/L; G is the concentration of AZ31 magnesium alloy is 10g The anodic polarization curve in the sodium phosphate aqueous solution of /L; h is the anodic polarization curve of AZ31 magnesium alloy in the sodium fluoride aqueous solution with concentration of 10g/L; i is the sodium carbonate of AZ31 magnesium alloy in the concentration of 10g/L Anodic polarization curve in aqueous solution; j is the anodic polarization curve of AZ31 magnesium alloy in potassium hydroxide aqueous solution with concentration of 10g/L; k is the concentration of AZ31 magnesium alloy in sodium phosphate concentration of 5g/L, potassium hydroxide concentration is the anodic polarization curve of the mixed aqueous solution of 1g/L; l is the mixed aqueous solution whose concentration of sodium phosphate is 5g/L, the concentration of potassium hydroxide is 1g/L, and the concentration of sodium fluoride is 5g/L for AZ31 magnesium alloy The anodic polarization curve in; m is the anodic polarization curve of AZ31 magnesium alloy in the mixed aqueous solution whose concentration of sodium phosphate is 5g/L, and the concentration of sodium silicate is 5g/L; n is the anodic polarization curve of AZ31 magnesium alloy in potassium hydroxide The anodic polarization curve in a mixed aqueous solution with a concentration of 1g/L and a concentration of sodium fluoride of 5g/L; o is AZ31 magnesium alloy in a concentration of sodium silicate of 5g/L and a concentration of sodium fluoride of 5g/L The anodic polarization curve in the mixed aqueous solution;

Fig. 3 is a passivation interval width diagram on the AZ31 magnesium alloy anodic polarization curve of test two;

Fig. 4 is a diagram of the polarization current on the anodic polarization curve of the second test AZ31 magnesium alloy before the passivation film becomes unstable.

Detailed ways

Specific implementation mode 1: The method for detecting the arcing characteristics of alloy micro-arc oxidation by using the anodic polarization curve in this embodiment is carried out according to the following steps:

1. Prepare the electrolyte to be verified;

Two, measure the anodic polarization curve with the voltage U as the abscissa and the current I as the ordinate in the electrolytic solution to be verified obtained in step 1;

3. On the anodic polarization curve measured in step 2, if there is no passivation zone, the alloy cannot undergo micro-arc oxidation in the electrolyte; if there is a passivation zone, the alloy can undergo micro-arc oxidation in the electrolyte Arc oxidation; the wider the passivation interval, the lower the voltage of the alloy in the electrolyte for micro-arc oxidation arc discharge; when the passivation interval is similar, the polarization current on the anodic polarization curve before the passivation film becomes unstable The smaller the value, the lower the arc discharge voltage of the alloy in the electrolyte, and thus the arc start characteristics of the alloy are obtained.

Compared with micro-arc oxidation, the method of this embodiment utilizes the condition of alloy anodic polarization curve, which is a process of low pressure and low current density, so that the process of judging the characteristics of alloy micro-arc oxidation can be simplified, and energy can be saved.

Embodiment 2: This embodiment differs from Embodiment 1 in that the alloy in step 2 is magnesium alloy, aluminum alloy or titanium alloy. Others are the same as in the first embodiment.

Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that the anodic polarization curve in step 2 is measured by a potentiostatic method. Others are the same as in the first or second embodiment.

Specific embodiment four: the difference between this embodiment and specific embodiment one or two is that the measuring method of the anodic polarization curve in step 2 is as follows: adopt the electrochemical comprehensive test platform of CHI604C, adopt three-electrode system, and reference electrode is Saturated calomel electrode, platinum electrode as the auxiliary electrode, the alloy to be tested as the anode, and the electrolyte to be verified as the corrosion medium; the potential measurement range is: scanning potential -2 to (6 ~ 9) V, scanning speed 0.01V/s , stand still for 10S before scanning; when the entire curve is scanned, the common voltage-current logarithmic curve is obtained, and the potential-current logarithmic curve is converted into a voltage-current curve, which is the required anodic polarization curve. Others are the same as in the first or second embodiment.

The present invention verifies the beneficial effect of the present invention with following test:

Test 1: In this test, the method of using the anodic polarization curve to detect the arcing characteristics of alloy micro-arc oxidation is carried out according to the following steps:

1. Prepare the electrolyte solution to be verified; among them, there are five kinds of electrolyte solutions to be verified, the first is a sodium silicate aqueous solution with a concentration of 10g/L, the second is a sodium phosphate aqueous solution with a concentration of 10g/L; the third is Concentration is the potassium chloride aqueous solution of 10g/L; The fourth kind is the concentration and is the sodium molybdate aqueous solution of 10g/L; The fifth kind is the sodium dihydrogen phosphate aqueous solution that the concentration is 10g/L;

2. The equipment and steps for determining the anodic polarization curve of the alloy by the constant potential method are: use the CHI604C electrochemical comprehensive test platform produced by Shanghai Chenhua Instrument Company to measure the anode electrode in the electrolyte to be verified for the AZ31 magnesium alloy obtained in step 1 The test process uses a three-electrode system, the reference electrode is a saturated calomel electrode, the auxiliary electrode is a platinum electrode, and the AZ31 magnesium alloy to be tested is used as the anode; the electrolyte to be verified is used as the corrosion medium; the potential measurement range is: scanning potential -2 to 9V, scan speed 0.01V/s, stand still for 10S before scanning, get the voltage-current logarithmic curve, and then convert the potential-current logarithmic curve into an anode with the voltage U as the abscissa and the current I as the ordinate Polarization curve;

3. On the anodic polarization curve measured in step 2, if there is no passivation zone, the alloy cannot undergo micro-arc oxidation in the electrolyte; if there is a passivation zone, the alloy can undergo micro-arc oxidation in the electrolyte Arc oxidation; the wider the passivation interval, the lower the voltage of the alloy in the electrolyte for micro-arc oxidation arc discharge; when the passivation interval is similar, the polarization current on the anodic polarization curve before the passivation film becomes unstable The smaller the value, the lower the arc discharge voltage of the alloy in the electrolyte, and thus the arc start characteristics of the alloy are obtained.

Wherein the anodic polarization curve recorded in step 2 is as shown in Figure 1, wherein a is the anodic polarization curve of the AZ31 magnesium alloy in the sodium silicate aqueous solution of 10g/L for the first kind of wherein a, and b is the second kind of Concentration is the anodic polarization curve of AZ31 magnesium alloy in sodium phosphate aqueous solution of 10g/L; c is the third kind is the anodic polarization curve of AZ31 magnesium alloy in potassium chloride aqueous solution with concentration of 10g/L; d is the fourth kind Concentration is the anodic polarization curve of AZ31 magnesium alloy in 10g/L sodium molybdate aqueous solution; e is the anodic polarization curve of AZ31 magnesium alloy in the sodium dihydrogen phosphate aqueous solution that concentration is 10g/L for the fifth;

As can be seen from Figure 1, there is no passivation interval on the anodic polarization curves of the three curves of c, d and e. Therefore, in the potassium chloride aqueous solution with a concentration of 10g/L or the aqueous solution of sodium molybdate with a concentration of 10g/L In the sodium dihydrogen phosphate aqueous solution of 10g/L, the AZ31 magnesium alloy cannot be subjected to micro-arc oxidation arc discharge; and there are passivation intervals on the two anode polarization curves of a and b. Therefore, in the concentration of 10g/L silicon In sodium phosphate aqueous solution or sodium phosphate aqueous solution with a concentration of 10g/L, AZ31 magnesium alloy can be subjected to micro-arc oxidation and arc discharge. This result is the same as the actually measured result.

Test 2: In this test, the method of using the anodic polarization curve to detect the arcing characteristics of alloy micro-arc oxidation is carried out according to the following steps:

1. Prepare the electrolyte to be verified; among them, there are the following ten electrolytes to be verified:

(1) concentration is the sodium silicate aqueous solution of 10g/L;

(2) concentration is the sodium phosphate aqueous solution of 10g/L;

(3) Aqueous sodium fluoride solution whose concentration is 10g/L;

(4) concentration is the sodium carbonate aqueous solution of 10g/L;

(5) Concentration is the potassium hydroxide aqueous solution of 10g/L;

(6) The concentration of sodium phosphate is 5g/L, and the concentration of potassium hydroxide is a mixed aqueous solution of 1g/L;

(7) The concentration of sodium phosphate is 5g/L, the concentration of potassium hydroxide is 1g/L, the concentration of sodium fluoride is the mixed aqueous solution of 5g/L;

(8) The concentration of sodium phosphate is 5g/L, the concentration of sodium silicate is the mixed aqueous solution of 5g/L;

(9) The concentration of potassium hydroxide is 1g/L, the concentration of sodium fluoride is the mixed aqueous solution of 5g/L;

(10) The concentration of sodium silicate is 5g/L, the concentration of sodium fluoride is the mixed aqueous solution of 5g/L;

2. The equipment and steps for determining the anodic polarization curve of the alloy by the constant potential method are: use the CHI604C electrochemical comprehensive test platform produced by Shanghai Chenhua Instrument Company to measure the anode electrode in the electrolyte to be verified for the AZ31 magnesium alloy obtained in step 1 The test process uses a three-electrode system, the reference electrode is a saturated calomel electrode, the auxiliary electrode is a platinum electrode, and the AZ31 magnesium alloy to be tested is used as the anode; the electrolyte to be verified is used as the corrosion medium; the potential measurement range is: scanning potential -2 to 9V, scan speed 0.01V/s, stand still for 10S before scanning, get the voltage-current logarithmic curve, and then convert the potential-current logarithmic curve into an anode with the voltage U as the abscissa and the current I as the ordinate Polarization curve;

3. On the anodic polarization curve measured in step 2, if there is no passivation zone, the alloy cannot undergo micro-arc oxidation in the electrolyte; if there is a passivation zone, the alloy can undergo micro-arc oxidation in the electrolyte Arc oxidation; the wider the passivation interval, the lower the voltage of the alloy in the electrolyte for micro-arc oxidation arc discharge; when the passivation interval is similar, the polarization current on the anodic polarization curve before the passivation film becomes unstable The smaller the value, the lower the arc discharge voltage of the alloy in the electrolyte, and thus the arc start characteristics of the alloy are obtained.

Wherein the anodic polarization curve measured in step 2 is as shown in Figure 2, among Fig. 2, f is the anodic polarization curve of AZ31 magnesium alloy in the sodium silicate aqueous solution that concentration is 10g/L; G is the anodic polarization curve of AZ31 magnesium alloy in The concentration is the anodic polarization curve in the sodium phosphate aqueous solution of 10g/L; h is the anodic polarization curve of the AZ31 magnesium alloy in the sodium fluoride aqueous solution with the concentration of 10g/L; i is the AZ31 magnesium alloy in the concentration of 10g/L The anodic polarization curve in the sodium carbonate aqueous solution; j is the anodic polarization curve of the AZ31 magnesium alloy in the potassium hydroxide aqueous solution whose concentration is 10g/L; Potassium concentration is the anodic polarization curve of the mixed aqueous solution of 1g/L; l is AZ31 magnesium alloy in the concentration of sodium phosphate is 5g/L, the concentration of potassium hydroxide is 1g/L, the concentration of sodium fluoride is 5g/L The anodic polarization curve in the mixed aqueous solution; m is the anodic polarization curve of the mixed aqueous solution in which the concentration of sodium phosphate and sodium silicate is 5g/L for AZ31 magnesium alloy; n is the anodic polarization curve of AZ31 magnesium alloy in hydrogen The concentration of potassium oxide is 1g/L, the concentration of sodium fluoride is the anodic polarization curve in the mixed aqueous solution of 5g/L; o is AZ31 magnesium alloy in the concentration of sodium silicate is 5g/L, the concentration of sodium fluoride is Anodic polarization curve in 5g/L mixed aqueous solution.

It can be seen from Figure 2 that there are passivation intervals on the anodic polarization curves of the AZ31 magnesium alloy in the ten electrolytes in this test. Arc discharge: Compared with micro-arc oxidation, the conditions for testing the alloy anodic polarization curve in this test method are a process of low pressure and low current density, which can simplify the process of judging the characteristics of alloy micro-arc oxidation, thereby saving energy.

The width of the passivation interval on the anodic polarization curve of AZ31 magnesium alloy in different electrolytes is shown in Figure 3, and the specific data are shown in Table 1.

Table 1 Width of passivation interval on the anodic polarization curve of AZ31 magnesium alloy in different electrolytes

serial number Electrolyte Passivation interval width (V) f 10g/L sodium silicate 4.94 g 10g/L sodium phosphate 4.95 h 10g/L sodium fluoride 4.82 i 10g/L of sodium carbonate 5.03 j 10g/L Potassium Hydroxide 5.12 k 5g/L Sodium Phosphate+1g/L Potassium Hydroxide 6.83 l 5g/L Sodium Phosphate+1g/L Potassium Hydroxide+5g/L Sodium Fluoride 9.95 m 5g/L Sodium Phosphate+5g/L Sodium Silicate 4.82 n 1g/L Potassium Hydroxide + 5g/L Sodium Fluoride 9.98 o 5g/L sodium silicate+5g/L sodium fluoride 9.96

On the anodic polarization curve, the wider the passivation interval, the lower the arc discharge voltage of AZ31 magnesium alloy micro-arc oxidation in the corresponding electrolyte; it can be seen from Table 1 that the arc discharge voltage of AZ31 magnesium alloy micro-arc oxidation The magnitude order of the voltage U is: (Ul, Un, Uo)<Uk<(Uf, Ug, Uh, Ui, Uj, Um)

When the width of the passivation interval on the anodic polarization curve of AZ31 magnesium alloy is similar, the smaller the polarization current before the passivation film on the anodic polarization curve becomes unstable, the higher the arc discharge voltage of magnesium alloy micro-arc oxidation in the corresponding electrolyte. Low.

In this test, in the electrolyte with similar passivation interval width, the polarization current before the passivation film layer becomes unstable is shown in Figure 4, and its specific values are shown in Table 2.

Table 2 Polarization current before the passivation film layer is unstable on the anodic polarization curve of AZ31 magnesium alloy in different electrolytes

It can be seen from Table 2 that the magnitude sequence of the arc discharge voltage U of AZ31 magnesium alloy micro-arc oxidation is:

Ul<Un<Uo;

Uj<Uh<Uf<Um<Ug<Ui

Comprehensively, it can be concluded that: Ul<Un<Uo<Uk<Uj<Uh<Uf<Um<Ug<Ui

The experimental results are the same as the predicted results. Compared with the micro-arc oxidation, the conditions for testing the anodic polarization curve of the alloy in this test method are a low-pressure, low-current-density process, which can simplify the process of judging the characteristics of the alloy micro-arc oxidation, thereby saving energy.

Claims (3)

1. Utilize the method of anodic polarization curve detection alloy micro-arc oxidation arc starting characteristic, it is characterized in that utilize anodic polarization curve to detect the method for alloy micro-arc oxidation arc starting characteristic to carry out as follows: 1. Prepare the electrolyte to be verified; Two, measure the anodic polarization curve with the voltage U as the abscissa and the current I as the ordinate in the electrolytic solution to be verified obtained in step 1; 3. On the anodic polarization curve measured in step 2, if there is no passivation zone, the alloy cannot undergo micro-arc oxidation in the electrolyte; if there is a passivation zone, the alloy can undergo micro-arc oxidation in the electrolyte Arc oxidation; the wider the passivation interval, the lower the voltage of the alloy in the electrolyte for micro-arc oxidation arc discharge; when the passivation interval is similar, the polarization current on the anodic polarization curve before the passivation film becomes unstable The smaller the value, the lower the arc discharge voltage of the alloy in the electrolyte; thus the arc start characteristics of the alloy are obtained; The measurement method of the anodic polarization curve in the described step 2 is as follows: the electrochemical comprehensive test platform of CHI604C is adopted, a three-electrode system is adopted, the reference electrode is a saturated calomel electrode, the auxiliary electrode is a platinum electrode, and the tested alloy is made of It is an anode, and the electrolyte to be verified is used as a corrosion medium; the potential measurement range is: scanning potential -2 to 6V ~ 9V, scanning speed 0.01V/s, and resting for 10S before scanning; when the entire curve is scanned, the common voltage is obtained - Current logarithmic curve, the potential-current logarithmic curve is converted into a voltage-current curve is the required anodic polarization curve. 2. The method according to claim 1, characterized in that the alloy in step 2 is magnesium alloy, aluminum alloy or titanium alloy. 3. The method according to claim 1 or 2, characterized in that the anodic polarization curve in step 2 is measured by a potentiostatic method.

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