TW200927999A - Acid solution and magnesium alloy phosphating method using the same - Google Patents

Abstract

The present invention relates to an acid solution used in a magnesium alloy phosphating method. The acid solution includes citric acid and no-silicon water-solubility surfactant. The concentration of the citric acid is in a range from 5 g/L to 30 g/L in the acid solution, the concentration of no-silicon water-solubility surfactant is in a range from 1. 5 g/L to 6 g/L in the acid solution. A method of magnesium alloy phosphating using the acid solution is also provided. Ash generated on surfaces of the magnesium alloy perform can be removed or reduced when the magnesium alloy perform is processed in the acid solution.

Description

200927999 IX. Description of the invention: [Technical field to which the invention pertains] * The present invention relates to a magnesium alloy phosphating method and an acid washing solution thereof. [Prior Art] Magnesium alloy light materials are widely used in automobiles and electrical equipment because of their low specific gravity, high strength and suitable for recycling. , quasi-, because the town alloy chemical properties are more active, corrosion resistance is poor, so magnesium alloy parts generally need to form anti-corrosion on the surface before use (10), the anti-corrosion (four) needs to have good fog performance, higher Adhesion and small surface impedance. In the prior art, a dense phosphating film is generally formed on the surface of a magnesium alloy workpiece by a phosphating method to improve its corrosion resistance. A conventional magnesium alloy phosphating method, including the pickling process step 'the main function of the pickling is to remove the oxide on the surface of the magnesium alloy workpiece and the release agent sprayed during the die casting, and increase the surface roughness of the alloy workpiece surface' However, in the conventional pickling process, black ash substances (main components are aluminum and ^) are easily generated on the surface of the magnesium alloy workpiece, and the black ash material is not easily removed in the subsequent alkali washing process, so that the subsequent phosphorus is formed. The film has uneven color, black color of the local color, and even defects such as floating ash on the surface of the alloy workpiece. SUMMARY OF THE INVENTION In view of the above circumstances, it is necessary to provide a town alloy phosphating method and a pickling liquid which can avoid or reduce the formation of a black ash substance on the surface of a magnesium alloy workpiece. A pickling solution for Zhenwei Weiweiyi, which comprises a splashing acid and a flawless water-soluble surfactant, wherein the concentration of citric acid in the pickling solution is 5 to 3 g/liter in the 200927999 solution. The concentration of the surfactant in the pickling solution is from 1.5 to 6 g/liter. The 'magnesium-gold phosphating method' comprises the steps of pickling, washing and forming into a filled film, wherein the pickling step uses an acid washing solution comprising citric acid and no water-soluble liquid. The surfactant, the concentration of the falling acid in the pickling solution is 5 to 3 G seven liters, and the concentration of the non-soluble surfactant in the pickling solution is 15 to 6 g/liter. In the above-mentioned town alloy phosphating method, by controlling the composition of the pickling solution, the cerium can completely remove the oxide and the releasing agent on the surface of the alloy alloy member, and can also avoid or reduce the formation of black on the surface of the alloy workpiece. Gray matter. [Embodiment] Hereinafter, a magnesium alloy workpiece and a magnesium alloy filling method of the present invention will be further described in detail with reference to the accompanying drawings and embodiments. 1 is a flow chart showing a magnesium alloy phosphating method according to a preferred embodiment of the present invention, which comprises the following steps: _ Step 10, providing a magnesium alloy pre-substrate; Step 20, degreasing, using a degreasing solution Removing the oil stain on the surface of the magnesium alloy pre-substrate; Step 30, pickling, removing the oxide and release agent on the surface of the magnesium alloy pre-substrate with an acid pick-up solution; Step 40' alkaline washing, removing the magnesium with an alkali washing solution The black ash material on the surface of the alloy pre-substrate; the step 50' is formed, and a bismuth is formed on the surface of the magnesium alloy pre-substrate by using a chemical conversion solution. 200927999 In step 20, the degreasing time can be controlled from 4 to 8 minutes, and the degreasing temperature can be controlled from 55 to 65 °C. The degreasing solution may be an aqueous solution of sodium cerium oxide (NaOH) or sodium phosphate (Na3P04). The degreasing process is mainly used to remove organic oil such as engine oil and cutting oil on the surface of the pre-base of the magnesium alloy. It can be understood that the step 20 can be omitted after the magnesium alloy pre-substrate is treated by sand blasting or the like, and the surface of the magnesium alloy pre-base is free of oil. In step 30, the pickling time can be controlled from 3 to 5 minutes, and the pickling temperature can be controlled from 35 to 45 °C. In this embodiment, the pickling solution comprises citric acid (industrial grade) (HOOCCH2C(OH)(COOH)CH2COOH) having a concentration of 5 to 30 g/l and a non-cutting water concentration of 1.5 to 6 g/l. Surfactant (industrial grade). The citric acid can be reacted with the oxide of the surface of the magnesium alloy pre-substrate and the release agent sprayed during the die-casting to remove the oxide and the release agent. The oxides which can be removed include magnesium oxide (MgO), aluminum oxide (Al2〇3), and zinc oxide (ZnO), etc.; the removable release agent includes sorghum organic matter (((CH2)m-CH(Si) n-COOR), wherein R is a functional group such as a thiol group. The citric acid in the pickling solution can simultaneously avoid or reduce the formation of black ash material on the surface of the magnesium alloy pre-substrate. The concentration of citric acid in the pickling solution is preferably from 8 to 15 g/l. In the pickling step, citric acid mainly undergoes the following chemical reactions:

Mg0 + 2H+=Mg2+ + H20; Α12〇3 + 6Η+=2Α13+ + 3Η20;

Zn0 + 2H+ = Zn2++H20 ;

Mg + 2H+=Mg2++H2 ; 200927999 The flawless water-soluble surfactant is used to make the surface reaction of magnesium alloy workpiece more uniform, and at the same time reduce the reaction speed, so that the reaction of citric acid is easier to control, thereby further avoiding or reducing pickling. During the process, excessive corrosion occurs on the surface of the magnesium alloy workpiece to form a black ash substance. The water-free solution: the surfactant is a low-foaming, water-free, nonionic surfactant whose hydrophilic group is mainly a hydroxyl group. The flawless water-soluble surfactant may be a polyol, such as diethylene glycol, glycerin, pentaerythritol, sucrose, glucose, more uniform reaction and avoiding waste. The concentration in the water-free surface sputum is preferably 3 to 4 g / liter. Sorbitol and the like. In order to dissolve the active agent in the acid wash in step 40, the alkali washing time may be 3 to 5 minutes, and the alkali washing temperature may be 60 to 80 °C. The base in the caustic wash solution may be potassium hydroxide (KOH) or sodium hydroxide (NaOH). Alkaline washing is used to react with the black ash material on the surface of the magnesium alloy pre-base to remove the black ash material and expose the magnesium alloy substrate. If industrial grade potassium hydroxide is used, the concentration in the alkali washing solution may be 6 〇 to 18 克 / liter; 〇 is to completely remove the black ash material and avoid local blackening of the surface of the subsequent phosphating film and avoid subsequent The surface of the resulting filled film has a large surface impedance, and potassium hydroxide is used for the washing; the degree of agronomy in the grain liquid is preferably from 1 to 150 g/liter. The following chemical reactions occur mainly in the hydration: 6ΚΟΗ+2Α1=2Κ3Α1〇3 + 3Η2 ; 2K0H+Zn=K2Zn02+H2. The time of formation in step 50 can be from 3 to 50 seconds, and the formation temperature can be from 35 to 45. (: The filling film formed on the surface of the magnesium alloy pre-substrate may be 5 to 30 microns, and the surface resistance of the magnesium alloy pre-substrate may be less than 2 ohms. The chemical solution may include 2.89 5 main 8.67 Gram / liter scale. • Acid (H3P04) (industrial grade), 0.3 to! g / liter of urea (analytical grade), Q 39 - to (10) g / liter of stone (HN 〇 3) (industrial grade), 6 i 3 g/L of dihydromanganese (Mr^HJO4) 2) (industrial grade) and 〇·2 to 〇·6 g/l of tannic acid (C76H52〇46) (analytical grade). The main role of phosphoric acid is to provide the acid ion ions needed to form the Wei film. The concentration of phosphoric acid in the formation solution is preferably from 4 34 to 65 g / liter. The main role of θ urea is to make the formed phosphating film more uniform. The concentration of urea in the chemical solution is preferably from 4 to 0.6 g/liter. The main function of nitric acid is to provide free hydrogen ions to adjust the pH of the solution to a pH of between 6.5 and 9.5. In order for the phosphating film to have better salt spray resistance and lower surface resistance, the concentration of nitric acid in the forming solution is preferably from 0.62 to 9.4 g/l. The main function of manganese monomanganese phosphate is to provide manganese ions, phosphate ions and ruthenium free hydrogen ions. The concentration of manganese dihydrogen phosphate in the formation solution is preferably from 丄〇 to 18 g/liter. The primary function of the monolithic SiL is to increase the adhesion between the squamous film and the subsequently applied paint layer on the structured film. The tannic acid is preferably from 0.4 to 0.55 g/liter in the formation solution. The time for forming the phosphating film may be from 30 seconds to 50 seconds. The main components of the formed phosphating film are complex phosphates such as magnesium phosphate (Mg3(p〇4)2) and manganese phosphate (Mn3(p〇4)2), and the main chemical reaction equations are as follows:

Mg+2H+=Mg2++H2; 200927999 3Mg2+ + 2P〇43 =Mg3(P〇4)2; 3Mn2++2P043_=Mn3(P04)2. The chemical formula of the composite phosphate may be: (Mg2+)A(Mn2+)B(N〇3)c(Zn2+)D(P043)E.... It can be understood that the at least one water washing step can be separately performed after the step 2, the step 30, the step 40 and the step 50, and the magnesium alloy workpiece can be baked after the step 5, wherein the baking time is 3〇 to 7〇 minutes' baking temperature is 11 () to i50 °c. In order to further explain the above-described magnesium alloy phosphating method, the following will be described by way of specific examples. €>

Provide three groups (the first group, the second group and the third group). The alloy pre-base material of the town is AZ91D dragon alloy. The process and parameters shown in the figure are as shown in the figure. The substrate is subjected to squaring treatment; and in the process of Wei treatment, the components of the first group and the second group of the third off alloy pre-substrate are used in the degreasing, pickling, caustic washing and chemical conversion processes. The concentrations are not as listed in the MkAme column. The results of the three sample mouth tests of the three groups of magnesium alloys OB, ^ ® 1 after P phosphating are shown in Fig. 4. Among them, the 醆 制 制 认 , , , , , , , , , , , , 使用 使用 使用 ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; In the town contract contract ^ 〇 τ 100 grid knife test. ♦ Increased, the use level can be seen from Figure 4, 'the surface impedance is less than 2 ohms. The salt spray test of both sets of samples exceeds 8 and the adhesion is greater than 3β. Visible

11 (S 200927999 The magnesium alloy workpiece treated by the magnesium alloy phosphating method of the invention has good salt spray resistance, high adhesion and small surface resistance. 'When the magnesium-gold workpiece is applied In the case of the portable electronic device, the portable electronic device can ensure a strong electromagnetic wave shielding capability. In summary, the present invention complies with the invention patent requirements, and the patent application is filed according to law. The invention is not limited to the above-described embodiments, and any equivalent modifications or variations made by those skilled in the art to the present invention should be included in the following patent applications. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart of a magnesium alloy phosphating method according to a preferred embodiment of the present invention. Fig. 2 Magnesium alloy phosphating process flow and parameter diagram Fig. 3 Degreasing and pickling during phosphating Solution formula for alkaline washing and chemical conversion steps. Figure 4 Sample test results. [Main component symbol description]

12

Claims (1)

200927999 . X. Patent Application Range 1. A pickling solution for magnesium alloy phosphating process, comprising citric acid and 'no water-soluble surfactant, wherein the concentration of citric acid in the pickling solution is 5 to 30 g / liter, the concentration of the water-free surfactant in the pickling solution is 1.5 to 6 g / liter. 2. The pickling solution for magnesium alloy phosphating process according to claim 1, wherein the concentration of the citric acid in the pickling solution is 8 to 15 g/l. 3. The pickling solution for magnesium alloy phosphating process according to claim 1, wherein the concentration of the water-free surfactant in the pickling solution is 3 to 4 g/liter. . 4. The acid washing solution for magnesium alloy walling process according to the above-mentioned claim, wherein the water-free surfactant is a polyol. 5. The acid sirloin solution for magnesium alloy sizing process according to claim 4, wherein the polyol is one of polyethylene glycol, glycerin, pentaerythritol, sucrose, glucose and sorbitol or a combination thereof. Things. 6·- magnesium alloy deuteration method, which comprises the steps of pickling, washing and forming into a phosphating film, wherein an acid washing solution comprising citric acid and water-free water is used in the pickling step. A surfactant wherein the concentration of citric acid in the pickling solution is 5 to 3 g/l and the concentration of the non-hydrophobic/exciting surfactant in the pickling solution is 6 g/l. 7. The magnesium alloy deuteration method according to claim 6, wherein the concentration of the citric acid in the pickling solution is from 8 to 15 g/l. 8. The method of phosphating a magnesium alloy according to claim 6, wherein the concentration of the water-soluble surfactant in the pickling solution is liter. 9. The magnesium alloy phosphating method according to claim 6, wherein the water-free surfactant is a polyol. 10. The magnesium alloy phosphating method according to claim 9, wherein the polyhydric alcohol is one of polyethylene glycol, glycerin, pentaerythritol, sucrose, glucose, and sorbitol or a combination thereof. ❹ 14