A film remover for wrought aluminum and die-cast aluminum composite parts and its preparation method

Abstract

This invention relates to the field of film removal agents, and more particularly to a film removal agent for wrought aluminum and die-cast aluminum composite parts and its preparation method. The raw materials, by weight percentage, include: 45%~75% acidic adhesive, 5%~15% oxidant, 4%~12% black film dissolving agent, 2%~7% corrosion inhibitor and adsorbent, 1%~10% chelating agent, and deionized water to make up the balance. The density of the film removal agent is 1.55g / mL~1.655g / mL, and the viscosity at 20℃ is 24mPa·s~36mPa·s. The concentration of free fluoride ions in the film removal agent is 3000ppm~9000ppm. The film removal agent provided by this invention can completely remove the black film from the surface of die-cast aluminum plates within 1 minute, and the gloss retention rate of the wrought aluminum substrate can reach over 94%. It has good film removal effect and minimal corrosion damage to the substrate, meeting the film removal processing requirements of wrought aluminum and die-cast aluminum composite parts.

Description

Technical Field

[0001] This invention relates to the field of film removal agents, and in particular to a film removal agent for wrought aluminum and die-cast aluminum composite parts and its preparation method. Background Technology

[0002] With the trend towards lightweight and integrated designs in consumer electronics, especially smartphones, laptops, and wearable devices, the materials used in their casings have evolved from engineering plastics to metal alloys. In recent years, aluminum alloys have become the preferred material for consumer electronics such as mobile phones, laptops, and wearables due to their excellent heat dissipation, good appearance, and structural strength. Traditional aluminum alloy casings are typically machined from wrought aluminum alloys (such as 6061 or 6063 alloys) using CNC machining. While this method offers high precision and good surface quality, it suffers from significant material waste, long processing times, and high costs for consumables such as cutting tools and machining fluids.

[0003] To reduce manufacturing costs while maintaining the aesthetic appeal of aluminum, the industry is increasingly shifting towards a combination of die-cast aluminum alloys and wrought aluminum alloys. The fuselage mid-plate, made of die-cast aluminum alloy (such as ADC12 or A380, typically with a high silicon content), is formed into a complex basic structure through high-pressure die casting. This structure is then welded to the outer frame made of wrought aluminum alloy, and key areas are finished with a small amount of CNC machining. Finally, anodizing is applied to the aluminum surface. This method significantly reduces material waste and processing time, lowering production costs by approximately 30% to 40%.

[0004] However, this composite structure of wrought aluminum and die-cast aluminum faces some technical challenges in the anodizing surface treatment of aluminum alloys: during alkaline washing and chemical polishing, a dense black film containing residues of silicon, copper, manganese, and other complex compounds forms on the surface of the die-cast aluminum alloy. To remove this black film and obtain a uniform surface, traditional processes typically use strong acidic film-removing agents containing fluorides (such as ammonium fluoride and hydrofluoric acid). Although fluorinated acidic film-removing agents can effectively remove the black film from die-cast aluminum, the fluorinated substances will cause severe and uncontrollable corrosion with the high-gloss wrought aluminum alloy, especially pitting corrosion at the grain boundaries. This destroys the high-gloss surface formed by mechanical polishing, cutting, and chemical polishing of the wrought aluminum, resulting in a significant decrease in gloss or even graying or darkening, failing to meet the high appearance and texture requirements of consumer electronics products.

[0005] Chinese invention patent application CN107723720A discloses an aluminum and aluminum alloy film removal agent and its application, comprising 200~600g / L of composite acid, 30~150g / L of composite oxidant, 2~20g / L of silicon stripping agent, 0.1~20g / L of corrosion inhibitor, 0.1~50g / L of stabilizer, 0.1~50g / L of ash removal agent and water; however, it takes a long time to remove impurities and some residues remain.

[0006] Therefore, there is an urgent need to develop a new type of film remover that can effectively remove ash from the surface of die-cast aluminum without damaging the deformed aluminum substrate and can maintain or even enhance the original high gloss of the deformed aluminum surface. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the first aspect of the present invention provides a film remover for wrought aluminum and die-cast aluminum composite parts, wherein the raw materials for preparation by weight percentage include: 45%~75% acidic adhesive, 5%~15% oxidant, 4%~12% black film dissolving agent, 2%~7% corrosion inhibitor and adsorbent, 1%~10% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.55 g / mL to 1.655 g / mL and a viscosity of 24 mPa·s to 36 mPa·s at 20°C. The concentration of free fluoride ions in the film-removing agent is 3000ppm~9000ppm.

[0008] Traditional pickling processes using nitric acid and hydrofluoric acid are insufficient to completely remove the black film and ash buildup on die-cast aluminum surfaces, and can even lead to over-corrosion. This invention addresses this issue by controlling the density of the film-removing agent to 1.55 g / mL to 1.655 g / mL, the viscosity at 20°C to 24 mPa·s to 36 mPa·s, and the concentration of free fluoride ions to 3000 ppm to 9000 ppm. This allows the film-removing agent to effectively remove the black film from the workpiece surface while simultaneously forming a uniform and dense protective film. This prevents excessive corrosion from fluoride ions and ensures a high-gloss finish on the workpiece surface.

[0009] In this system, high viscosity and density form a stable diffusion layer, creating a concentration gradient of aluminum ions on the surface. Microscopic protrusions experience rapid corrosion due to the low resistance of the diffusion layer, while recessed areas experience slow corrosion due to high resistance, thus achieving a "self-smoothing" effect and maintaining macroscopic surface gloss. Simultaneously, when the fluoride ion concentration in the film-removing agent is appropriate, it can efficiently break silicon-oxygen bonds and dissolve the black film; however, the diffusion layer resistance limits its penetration depth, preventing excessive fluoride ions from attacking the grain boundaries of the wrought aluminum and die-cast aluminum alloys. Too low a concentration results in incomplete removal of the black film, while too high a concentration increases the risk of surface corrosion in the wrought aluminum alloy, reducing its surface gloss.

[0010] In some embodiments, the acidic mucosal agent includes one or more of sulfuric acid, methylsulfuric acid, nitric acid, boric acid, hydrochloric acid, phosphoric acid, polyphosphoric acid, tripolyphosphoric acid, pyrophosphate, trimetaphosphoric acid, tetrametaphosphoric acid, tartaric acid, salicylic acid, formic acid, acetic acid, oxalic acid, propionic acid, butyric acid, succinic acid, lactic acid, glutaric acid, adipic acid, benzoic acid, phenylacetic acid, terephthalic acid, benzenesulfonic acid, methylbenzenesulfonic acid, fumaric acid, and maleic acid.

[0011] Acidic adhesives can provide the necessary acidic environment for the dissolution of the black film, dissolving silicon, manganese, copper and their oxides in the die-cast aluminum black film; on the other hand, they can change the interfacial properties of silicon and intermetallic compounds in the black film, making the black film easier to dissolve and peel off.

[0012] Optionally, the acidic mucosal agent includes at least one of sulfuric acid and phosphoric acid.

[0013] Optionally, the acidic mucosal agent comprises sulfuric acid and phosphoric acid, wherein the mass ratio of sulfuric acid to phosphoric acid is (10-30):(45-60). Examples include 10:60, 15:60, 15:45, 20:50, 30:45, or any value within the range of (10-30):(45-60).

[0014] In some embodiments, the oxidant includes one or more of the following: nitric acid, sodium nitrate, potassium nitrate, ferric nitrate, copper nitrate, hydrogen peroxide, peracetic acid, lithium persulfate, sodium persulfate, potassium persulfate, ammonium persulfate, lithium permanganate, potassium permanganate, sodium permanganate, ferric permanganate, lithium manganate, sodium manganate, potassium manganate, potassium perhydrosulfate, sodium perhydrosulfate, sodium perchlorate, ferric sulfate, ferric chloride, sodium ferrate, sodium chlorate, sodium hypochlorite, sodium percarbonate, sodium perborate, potassium perborate, sodium molybdate, potassium molybdate, sodium tungstate, and potassium tungstate.

[0015] Under acidic conditions, adding oxidizing agents oxidizes the inert components such as silicon, manganese, and copper in the black film on the surface of die-cast aluminum, transforming them into oxides. These oxides are then quickly dissolved by acidic or fluorine-containing substances. Furthermore, the passivating effect of the oxidant is more beneficial in protecting the wrought aluminum alloy from excessive corrosion. In this invention, the oxidant content is controlled at 5% to 15% by mass. If the oxidant content is too low, the oxidizing power is insufficient, failing to completely oxidize the inert components in the die-cast aluminum, thus reducing the efficiency of black film removal or resulting in poor film removal, and failing to provide passivation protection for the wrought aluminum. Conversely, if the oxidant content is too high, the system solution density or viscosity will be too low, easily leading to excessive corrosion of the wrought aluminum alloy surface and reducing surface gloss.

[0016] Optionally, the oxidant may include nitric acid.

[0017] Optionally, the oxidant includes nitric acid and hydrogen peroxide, wherein the mass ratio of nitric acid to hydrogen peroxide is (6-10):(1-5). Examples include 8:2, 10:2, 9:3, or any value within the range of (6-10):(1-5).

[0018] Optionally, the oxidant includes nitric acid and potassium persulfate, wherein the mass ratio of nitric acid to potassium persulfate is (6-10):(1-5). Examples include 8:2, 10:2, 9:3, or any value within the range of (6-10):(1-5).

[0019] In some embodiments, the black film solvent includes one or more of the following: hydrofluoric acid, potassium fluoride, sodium fluoride, ammonium fluoride, calcium fluoride, magnesium fluoride, ammonium hydrogen fluoride, sodium hydrogen fluoride, sodium fluoroborate, potassium fluoroborate, ammonium fluoroborate, zinc fluoroborate, fluorosilicic acid, sodium fluorosilicate, potassium fluorosilicate, fluorozirconic acid, potassium fluorozirconate, sodium fluorozirconate, fluorotitanic acid, potassium fluorotitanic acid, sodium fluorotitanic acid, lithium fluorotitanic acid, aluminum fluorotitanic acid, sodium fluoroaluminate, hexafluorophosphate, and tetrabutylammonium fluoroborate.

[0020] Die-cast aluminum alloys contain elemental silicon, silicon solid solutions, and silicon-containing intermetallic compounds. A fluorine-containing black film solvent is used, taking advantage of the small size and high electronegativity of fluoride ions, which exhibit strong nucleophilicity. After fluoride ions attack silicon atoms, the fluorine atoms bond with the silicon, causing the silicon-oxygen bonds to break. As the reaction proceeds, the oxygen atoms surrounding the silicon atoms are gradually replaced by fluorine atoms, forming soluble silicon tetrafluoride, thereby removing the black film from the substrate surface.

[0021] In some embodiments, the black film solvent includes at least one of hydrofluoric acid, ammonium fluoride, and fluorosilicic acid.

[0022] Optionally, the black film solvent includes hydrofluoric acid.

[0023] Optionally, the black film solvent includes ammonium fluoride.

[0024] Optionally, the black film solvent includes ammonium fluoride and fluorosilicic acid, wherein the mass ratio of ammonium fluoride to fluorosilicic acid is (8-10):(1-5). Examples include 8:2, 10:2, 9:3, or any value within the range of (8-10):(1-5).

[0025] Optionally, the black film solvent comprises hydrofluoric acid and ammonium fluoride, wherein the mass ratio of hydrofluoric acid to ammonium fluoride is (2-6):(2-6). Examples include 4:4, 2:6, 4:2, or any value within the range of (2-6):(2-6).

[0026] In some embodiments, the corrosion inhibitor includes one or more of N,N-dimethylformamide, urea, thiourea, acrylamide, caprolactam, lysine, arginine, histidine, aspartic acid, glutamic acid, serine, threonine, asparagine, glutamine, isoleucine, methionine, proline, tyrosine, imidazole, 2-methylimidazolium, 4-methylimidazolium, N-hexylimidazolium, hexadecylimidazolium, imidazoline, 1-butyl-3-methylimidazolium hexafluorophosphate, benzimidazole, ketoconazole, N-vinylimidazolium, benzotriazole, methylbenzotriazole, 1,2,3-triazole, 1,2,4-triazole, tetrazolium, 5-aminotetrazole mercaptobenzothiazole sodium, and imidazoline oleate.

[0027] In some embodiments, the corrosion inhibitor includes N-hexylimidazole.

[0028] Corrosion inhibitors can form an adsorption film on the surface of wrought aluminum. The lone pairs of electrons in the polar groups form coordinate bonds with the empty orbitals of Al atoms on the aluminum alloy surface, resulting in strong chemical adsorption. In particular, when the molecule contains long alkyl chains (such as N-hexylimidazole), these hydrophobic chains will be oriented on the alloy surface to form a dense barrier film, preventing the wrought aluminum surface from being attacked and corroded by fluoride ions and protecting the gloss of the wrought aluminum alloy surface.

[0029] Optionally, the corrosion inhibitor comprises N-hexylimidazole and thiourea; the mass ratio of N-hexylimidazole to thiourea is (3-6):(1-2). Examples include 3:1, 3:2, 4:1, or any value within the range of (3-6):(1-2).

[0030] Optionally, the corrosion inhibitor comprises N-hexylimidazole and aspartic acid; the mass ratio of N-hexylimidazole to aspartic acid is (3-6):(1-2). Examples include 3:1, 3:2, 4:1, or any value within the range of (3-6):(1-2).

[0031] In some embodiments, the chelating agent includes ethylenediaminetetraacetic acid, disodium EDTA, tetrasodium EDTA, diethylenetriaminepentaacetic acid, hypozoxytriacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid, citric acid, sodium tartrate, sodium gluconate, oxalic acid, malic acid, hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, diethylenetriaminepentamethylphosphonic acid, 2-phosphonobutane-1,2, One or more of the following: 4-tricarboxylic acid, sodium polyacrylate, polyaspartic acid, o-phenanthroline, 2,2′-bipyridine, 8-hydroxyquinoline, dimercaptosuccinic acid, sodium dimercaptopropanesulfonate, glutathione, acetylacetone, cyclodextrin, sodium tripolyphosphate, sodium ethylenediaminetetramethylenephosphonate, ethylenediaminetetramethylenephosphonic acid, 2-hydroxyphosphonoacetic acid, hexamethylenediaminetetramethylphosphonic acid, trisodium N,N-di(carboxymethyl)alanine, polyaminopolyether methylenephosphonic acid, and polyol phosphate.

[0032] Chelating agents can form stable complexes with metal ions in die-cast aluminum black films, accelerating the peeling of black films while preventing the peeled impurities from redepositing on the metal surface.

[0033] In some embodiments, the chelating agent includes at least one of sodium gluconate and sodium tartrate.

[0034] The second aspect of the present invention provides a method for preparing a film remover, comprising at least the following steps: mixing an acidic film remover, an oxidant, a black film dissolving agent, a corrosion inhibitor, a chelating agent, and deionized water to obtain the film remover for the wrought aluminum and die-cast aluminum composite parts.

[0035] The present invention also provides a film removal method using the above-mentioned film removal agent, the method comprising the following steps: After the workpiece is degreased, washed with water three times, chemically polished, and washed with water three times in sequence, it is placed in the film removal agent and left to stand for 30-60 seconds. Then it is taken out and washed with water three more times, and dried to complete the film removal of the workpiece.

[0036] Beneficial effects: (1) By controlling the density of the film remover to 1.55 g / mL to 1.655 g / mL, the viscosity at 20℃ to 24 mPa·s to 36 mPa·s, and the concentration of free fluoride ions to 3000 ppm to 9000 ppm, the film remover can effectively remove the black film on the surface of die-cast aluminum while quickly forming a uniform and dense protective film on the surface of the workpiece, avoiding excessive corrosion of the workpiece by fluoride ions and ensuring the high gloss texture of the workpiece surface.

[0037] (2) The film remover prepared by the present invention using specific raw materials can completely remove the black film and ash residue of silicon, manganese, copper and other compounds remaining on the surface of deformed aluminum and die-cast aluminum parts after alkaline washing or chemical polishing.

[0038] (3) By adding a specific corrosion inhibitor, the present invention can adsorb and form a dense barrier film on the surface of deformed aluminum. During the process of removing dust and film, fluoride ions cannot penetrate the dense barrier film, thereby protecting the high-gloss surface of deformed aluminum alloy from losing its luster due to corrosion.

[0039] (4) The film removal agent provided by the present invention improves the film removal efficiency and can completely remove the black film on the surface of die-cast aluminum plate within 1 minute. The gloss retention rate of the deformed aluminum substrate can reach more than 94%. The film removal effect is good and the corrosion damage to the substrate is small, which meets the film removal processing requirements of the combination of deformed aluminum and die-cast aluminum. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. Experimental methods not specifying specific conditions in the embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials, consumables, and equipment used in this invention are all commercially available.

[0041] The information on each raw material in the following examples and comparative examples is as follows: The phosphoric acid is an aqueous solution of phosphoric acid with a mass fraction of 85%.

[0042] The sulfuric acid is an aqueous solution of sulfuric acid with a mass fraction of 98%.

[0043] The nitric acid is an aqueous solution of nitric acid with a mass fraction of 68%.

[0044] The hydrogen peroxide is a 35% (w / w) aqueous solution of hydrogen peroxide.

[0045] The hydrofluoric acid is a 50% hydrofluoric acid aqueous solution.

[0046] The density test method is the Widmanstätten balance method, referring to GB / T611-2021.

[0047] The viscosity test method is rotational viscosity method, referring to GB / T10247-2008.

[0048] Example 1 The first aspect of this example provides a film remover for wrought aluminum and die-cast aluminum composite parts. The raw materials for preparation include, by weight percentage: 75% acidic adhesive, 10% oxidant, 8% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.618 g / mL and a viscosity of 35.74 mPa·s at 20°C. The concentration of free fluoride ions in the film-removing agent is 6102 ppm.

[0049] The acidic mucosal agent is phosphoric acid.

[0050] The oxidant is nitric acid.

[0051] The black film solvent is ammonium fluoride.

[0052] The corrosion inhibitor is N-hexylimidazole.

[0053] The chelating agent is sodium gluconate.

[0054] The second aspect of this example provides a method for preparing a film remover, comprising the following steps: mixing an acidic film remover, an oxidant, a black film dissolving agent, a corrosion inhibitor, a chelating agent, and deionized water to obtain the film remover for the wrought aluminum and die-cast aluminum composite parts.

[0055] Example 2 The specific implementation method in this example is the same as in Example 1, except that the density of the film-removing agent is 1.655 g / mL and the viscosity at 20°C is 28.84 mPa·s. The concentration of free fluoride ions in the film-removing agent is 6273 ppm.

[0056] The acidic mucosal agent is composed of phosphoric acid and sulfuric acid, with a mass ratio of 45:30.

[0057] Example 3 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 70% acidic mucosal agent, 15% oxidant, 8% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.628 g / mL and a viscosity of 28.845 mPa·s at 20°C. The concentration of free fluoride ions in the film-removing agent is 6129 ppm.

[0058] The acidic mucosal agent is composed of phosphoric acid and sulfuric acid, with a mass ratio of 50:20.

[0059] Example 4 The specific implementation method of this example is the same as that of Example 3, except that, by weight percentage, the raw materials include: 70% acidic mucosal agent, 5% oxidant, 8% black film dissolving agent, 5% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.58 g / mL and a viscosity of 28.856 mPa·s at 20°C. The concentration of free fluoride ions in the film-removing agent is 6164 ppm.

[0060] The corrosion inhibitor is N-hexylimidazolium and aspartic acid, and the mass ratio of N-hexylimidazolium to aspartic acid is 3:2.

[0061] The chelating agent is sodium tartrate.

[0062] Example 5 The specific implementation method of this example is the same as that of Example 3, except that, by weight percentage, the raw materials include: 70% acidic mucosal agent, 10% oxidant, 4% black film dissolving agent, 5% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.57 g / mL and a viscosity of 28.805 mPa·s at 20°C. The concentration of free fluoride ions in the film-removing agent is 3081 ppm.

[0063] The corrosion inhibitor is N-hexylimidazole and thiourea, and the mass ratio of N-hexylimidazole to thiourea is 3:2.

[0064] The chelating agent is sodium tartrate.

[0065] Example 6 The specific implementation method of this example is the same as that of Example 3, except that, by weight percentage, the raw materials include: 70% acidic mucosal agent, 10% oxidant, 11.5% black film dissolving agent, 2.5% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.636 g / mL and a viscosity of 28.905 mPa·s at 20°C. The concentration of free fluoride ions in the film-removing agent is 8743 ppm.

[0066] The black film solvent is ammonium fluoride and fluorosilicic acid, and the mass ratio of ammonium fluoride to fluorosilicic acid is 10:2.

[0067] The chelating agent is sodium tartrate.

[0068] Example 7 The specific implementation method of this example is the same as that of Example 3, except that, by weight percentage, the raw materials include: 70% acidic mucosal agent, 10% oxidant, 12% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.57 g / mL and a viscosity of 28.677 mPa·s at 20°C. The concentration of free fluoride ions in the film-removing agent is 8550 ppm.

[0069] The black film solvent is hydrofluoric acid.

[0070] The chelating agent is sodium tartrate.

[0071] Example 8 The specific implementation method of this example is the same as that of Example 3, except that, by weight percentage, the raw materials include: 75% acidic mucosal agent, 10% oxidant, 6% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.58 g / mL and a viscosity of 32.136 mPa·s at 20°C. The concentration of free fluoride ions in the film-removing agent is 4275 ppm.

[0072] The acidic mucosal agent is composed of sulfuric acid and phosphoric acid, with a mass ratio of sulfuric acid to phosphoric acid of 15:60.

[0073] The oxidizing agent is nitric acid and potassium persulfate, with a mass ratio of 8:2 for nitric acid and potassium persulfate.

[0074] The black film solvent is hydrofluoric acid.

[0075] Example 9 The specific implementation method of this example is the same as that of Example 3, except that, by weight percentage, the raw materials include: 70% acidic mucosal agent, 10% oxidant, 8% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.55 g / mL and a viscosity of 31.066 mPa·s at 20°C. The concentration of free fluoride ions in the film-removing agent is 5931 ppm.

[0076] The acidic mucosal agent is composed of sulfuric acid and phosphoric acid, with a mass ratio of sulfuric acid to phosphoric acid of 10:60.

[0077] The oxidant is nitric acid and hydrogen peroxide, with a mass ratio of 8:2 for nitric acid and hydrogen peroxide.

[0078] The black film solvent is hydrofluoric acid and ammonium fluoride, and the mass ratio of hydrofluoric acid to ammonium fluoride is 4:4.

[0079] Example 10 The specific implementation method of this example is the same as that of Example 3, except that, by weight percentage, the raw materials include: 60% acidic mucosal agent, 10% oxidant, 11.5% black film dissolving agent, 6.5% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.554 g / mL and a viscosity of 25.537 mPa·s at 20°C. The concentration of free fluoride ions in the film-removing agent is 8797 ppm.

[0080] The acidic mucosal agent is composed of sulfuric acid and phosphoric acid, with a mass ratio of sulfuric acid to phosphoric acid of 14:45.

[0081] The oxidant is nitric acid and hydrogen peroxide, with a mass ratio of 8:2 for nitric acid and hydrogen peroxide.

[0082] The black film solvent is ammonium fluoride and fluorosilicic acid, and the mass ratio of ammonium fluoride to fluorosilicic acid is 10:2.

[0083] The chelating agent is sodium tartrate.

[0084] Comparative Example 1 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 30% acidic mucosal agent, 10% oxidant, 8% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The density of the film-removing agent is 1.25 g / mL; The film-removing agent has a viscosity of 15.04 mPa·s at 20°C; The concentration of free fluoride ions in the film-removing agent is 6035 ppm.

[0085] Comparative Example 2 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 80% acidic mucosal agent, 5% oxidant, 8% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The density of the film-removing agent is 1.633 g / mL; The film-removing agent has a viscosity of 38.035 mPa·s at 20°C; The concentration of free fluoride ions in the film-removing agent is 6262 ppm.

[0086] Comparative Example 3 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 70% acidic mucosal agent, 10% oxidant, 8% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The density of the film-removing agent is 1.65 g / mL; The film-removing agent has a viscosity of 17.34 mPa·s at 20°C; The concentration of free fluoride ions in the film-removing agent is 6133 ppm.

[0087] The acidic mucosal agent is sulfuric acid.

[0088] Comparative Example 4 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 55% acidic mucosal agent, 25% oxidant, 8% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The density of the film-removing agent is 1.539 g / mL; The film-removing agent has a viscosity of 24.255 mPa·s at 20°C; The concentration of free fluoride ions in the film-removing agent is 6113 ppm.

[0089] The acidic mucosal agent is composed of sulfuric acid and phosphoric acid, with a mass ratio of sulfuric acid to phosphoric acid of 10:45.

[0090] Comparative Example 5 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 70% acidic mucosal agent, 10% oxidant, 12% black film dissolving agent, 0.5% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The density of the film-removing agent is 1.623 g / mL; The film-removing agent has a viscosity of 28.875 mPa·s at 20°C; The concentration of free fluoride ions in the film-removing agent is 9243 ppm.

[0091] The acidic mucosal agent is composed of sulfuric acid and phosphoric acid, with a mass ratio of sulfuric acid to phosphoric acid of 20:50.

[0092] The black film solvent is ammonium fluoride and fluorosilicic acid, and the mass ratio of ammonium fluoride to fluorosilicic acid is 10:2.

[0093] The chelating agent is sodium tartrate.

[0094] Comparative Example 6 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 70% acidic mucosal agent, 10% oxidant, 10% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The density of the film-removing agent is 1.661 g / mL; The film-removing agent has a viscosity of 31.34 mPa·s at 20°C; The concentration of free fluoride ions in the film-removing agent is 7703 ppm.

[0095] The acidic mucosal agent is composed of sulfuric acid and phosphoric acid, with a mass ratio of sulfuric acid to phosphoric acid of 10:60.

[0096] The oxidant is potassium persulfate.

[0097] The corrosion inhibitor is thiourea.

[0098] Comparative Example 7 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 66% acidic mucosal agent, 10% oxidant, 14% black film dissolving agent, 4% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The density of the film-removing agent is 1.575 g / mL; The film-removing agent has a viscosity of 31.23 mPa·s at 20°C; The concentration of free fluoride ions in the film-removing agent is 10703 ppm.

[0099] The acidic mucosal agent is composed of sulfuric acid and phosphoric acid, with a mass ratio of sulfuric acid to phosphoric acid of 10:56.

[0100] The black film solvent is hydrofluoric acid and ammonium fluoride, and the mass ratio of hydrofluoric acid to ammonium fluoride is 4:10.

[0101] The oxidant is hydrogen peroxide.

[0102] Comparative Example 8 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 70% acidic mucosal agent, 10% oxidant, 1% black film dissolving agent, 4% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The density of the film-removing agent is 1.581 g / mL; The film-removing agent has a viscosity of 31.23 mPa·s at 20°C; The concentration of free fluoride ions in the film-removing agent is 770 ppm.

[0103] The acidic mucosal agent is composed of sulfuric acid and phosphoric acid, with a mass ratio of sulfuric acid to phosphoric acid of 10:60.

[0104] Comparative Example 9 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 60% acidic mucosal agent, 5% oxidant, 20% black film dissolving agent, 4% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The density of the film-removing agent is 1.636 g / mL; The film-removing agent has a viscosity of 29.215 mPa·s at 20°C; The concentration of free fluoride ions in the film-removing agent is 19257 ppm.

[0105] The black film solvent is hydrofluoric acid and ammonium fluoride, and the mass ratio of hydrofluoric acid to ammonium fluoride is 2:18.

[0106] Comparative Example 10 The specific implementation method of this example is the same as that of Example 1, except that, by weight percentage, the raw materials include: 66% acidic mucosal agent, 15% oxidant, 12% black film dissolving agent, 2% corrosion inhibitor and adsorbent, 1.5% chelating agent, and deionized water to make up the balance. The density of the film-removing agent is 1.612 g / mL; The film-removing agent has a viscosity of 31.121 mPa·s at 20°C; The concentration of free fluoride ions in the film-removing agent is 9327 ppm.

[0107] The acidic mucosal agent is composed of sulfuric acid and phosphoric acid, with a mass ratio of sulfuric acid to phosphoric acid of 10:56.

[0108] The black film solvent is hydrofluoric acid and ammonium fluoride, and the mass ratio of hydrofluoric acid to ammonium fluoride is 4:8.

[0109] The corrosion inhibitor adsorbent is aspartic acid.

[0110] Performance testing Twenty wrought aluminum and die-cast aluminum composite parts with consistent initial surface conditions were sequentially subjected to degreasing (Ritteran RTL-5436, 50 g / L, 60℃, 180 s), three water washes, chemical polishing (1200 g / L 85% phosphoric acid, 400 g / L 98% sulfuric acid, 85℃, 90 s), and three water washes. They were then placed in the film-removing agents prepared in the respective examples and comparative examples for static film removal. After removal, they were washed three more times with water, dried, and observed (80℃, 15 min). The static film removal time and test results for each example and comparative example are shown in Table 1 below.

[0111] (1) Judgment of black film on the surface of the middle plate: ○ indicates no black film layer and the film is clean; ● indicates serious black film residue; ◎ indicates serious black film residue; ⊙ indicates a small amount of black film residue.

[0112] (2) The gloss was measured by a BYK4561 gloss meter at a 60-degree angle. The gloss retention rate is the ratio of the gloss of the outer frame deformed aluminum after film removal to the gloss of the outer frame deformed aluminum before film removal.

[0113] Table 1

[0114] As shown in Table 1, the film-removing agents prepared in each embodiment of the present invention can completely remove the black film on the surface of die-cast aluminum plate within 1 minute, and the gloss retention rate of the deformed aluminum substrate can reach more than 94%. The film removal effect is good and the corrosion damage to the substrate is small, which meets the film removal processing requirements of the combination of deformed aluminum and die-cast aluminum. However, the film-removing agents in each comparative example all have the problem of black film residue, and the gloss retention rate of the deformed aluminum substrate is generally less than 70%, which is far worse than the performance of the embodiments of the present invention. This shows that the present invention achieves efficient removal of black film on die-cast aluminum by adjusting the composition and ratio of raw materials, while effectively protecting the deformed aluminum substrate from excessive corrosion, and is suitable for the processing requirements of the combination of deformed aluminum and die-cast aluminum.

[0115] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A film remover for wrought aluminum and die-cast aluminum composite parts, characterized in that, The raw materials for preparation, by weight percentage, include: 45%~75% acidic adhesive, 5%~15% oxidant, 4%~12% black film solvent, 2%~7% corrosion inhibitor and adsorbent, 1%~10% chelating agent, and deionized water to make up the balance. The film-removing agent has a density of 1.55 g / mL to 1.655 g / mL and a viscosity of 24 mPa·s to 36 mPa at 20°C. The concentration of free fluoride ions in the film-removing agent is 3000ppm~9000ppm.

2. The film-removing agent according to claim 1, characterized in that, The acidic mucosal agent includes one or more of the following: sulfuric acid, methylsulfuric acid, nitric acid, boric acid, hydrochloric acid, phosphoric acid, polyphosphoric acid, tripolyphosphoric acid, pyrophosphate, trimetaphosphoric acid, tetrametaphosphoric acid, tartaric acid, salicylic acid, formic acid, acetic acid, oxalic acid, propionic acid, butyric acid, succinic acid, lactic acid, glutaric acid, adipic acid, benzoic acid, phenylacetic acid, terephthalic acid, benzenesulfonic acid, methylbenzenesulfonic acid, fumaric acid, and maleic acid.

3. The film-removing agent according to claim 1, characterized in that, The oxidizing agent includes one or more of the following: nitric acid, sodium nitrate, potassium nitrate, ferric nitrate, copper nitrate, hydrogen peroxide, peracetic acid, lithium persulfate, sodium persulfate, potassium persulfate, ammonium persulfate, lithium permanganate, potassium permanganate, sodium permanganate, ferric permanganate, lithium manganate, sodium manganate, potassium manganate, potassium perhydrosulfate, sodium perhydrosulfate, sodium perchlorate, ferric sulfate, ferric chloride, sodium ferrate, sodium chlorate, sodium hypochlorite, sodium percarbonate, sodium perborate, potassium perborate, sodium molybdate, potassium molybdate, sodium tungstate, and potassium tungstate.

4. The film-removing agent according to claim 3, characterized in that, The oxidizing agent includes nitric acid.

5. The film-removing agent according to claim 1, characterized in that, The black film solvent includes one or more of the following: hydrofluoric acid, potassium fluoride, sodium fluoride, ammonium fluoride, calcium fluoride, magnesium fluoride, ammonium hydrogen fluoride, sodium hydrogen fluoride, sodium fluoroborate, potassium fluoroborate, ammonium fluoroborate, zinc fluoroborate, fluorosilicic acid, sodium fluorosilicate, potassium fluorosilicate, fluorozirconic acid, potassium fluorozirconate, sodium fluorozirconate, fluorotitanic acid, potassium fluorotitanic acid, sodium fluorotitanic acid, lithium fluorotitanic acid, aluminum fluorotitanic acid, sodium fluoroaluminate, hexafluorophosphate, and tetrabutylammonium fluoroborate.

6. The film-removing agent according to claim 5, characterized in that, The black film solvent includes at least one of hydrofluoric acid, ammonium fluoride, and fluorosilicic acid.

7. The film-removing agent according to claim 1, characterized in that, The corrosion inhibitor adsorbent includes one or more of N,N-dimethylformamide, urea, thiourea, acrylamide, caprolactam, lysine, arginine, histidine, aspartic acid, glutamic acid, serine, threonine, asparagine, glutamine, isoleucine, methionine, proline, tyrosine, imidazole, 2-methylimidazolium, 4-methylimidazolium, N-hexylimidazolium, hexadecylimidazolium, imidazoline, 1-butyl-3-methylimidazolium hexafluorophosphate, benzimidazole, ketoconazole, N-vinylimidazolium, benzotriazole, methylbenzotriazole, 1,2,3-triazole, 1,2,4-triazole, tetrazolium, 5-aminotetrazole mercaptobenzothiazole sodium, and imidazoline oleate.

8. The film-removing agent according to claim 7, characterized in that, The corrosion inhibitor includes N-hexylimidazole.

9. The film-removing agent according to claim 1, characterized in that, The chelating agents include ethylenediaminetetraacetic acid, disodium EDTA, tetrasodium EDTA, diethylenetriaminepentaacetic acid, hypozoxytriacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid, citric acid, sodium tartrate, sodium gluconate, oxalic acid, malic acid, hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, diethylenetriaminepentamethylphosphonic acid, and 2-phosphonobutane-1,2,4-tricarboxylic acid. Sodium polyacrylate, polyaspartic acid, o-phenanthroline, 2,2′-bipyridine, 8-hydroxyquinoline, dimercaptosuccinic acid, sodium dimercaptopropanesulfonate, glutathione, acetylacetone, cyclodextrin, sodium tripolyphosphate, sodium ethylenediaminetetramethylenephosphonate, ethylenediaminetetramethylenephosphonic acid, 2-hydroxyphosphonoacetic acid, hexamethylenediaminetetramethylphosphonic acid, trisodium N,N-di(carboxymethyl)alanine, polyaminopolyether methylenephosphonic acid, and polyol phosphate esters are among one or more of these.

10. A method for preparing a film-removing agent according to any one of claims 1-9, characterized in that, The process includes at least the following steps: mixing an acidic adhesive, an oxidant, a black film dissolving agent, a corrosion inhibitor, a chelating agent, and deionized water to obtain a film remover for the wrought aluminum and die-cast aluminum composite parts.

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