Cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts

Abstract

The invention discloses a cyanide-free cadmium-iron alloy plating process for an aerospace titanium alloy part. An impact nickel plating layer, a cyanide-free copper plating layer, a cyanide-free cadmium-iron alloy plating layer, a passivation layer and a graphene modified sealing layer are sequentially prepared on a titanium alloy matrix from inside to outside. According to the cyanide-free cadmium iron alloy electroplating process, 25-35 g / L of cadmium chloride, 4-6 g / L of ferrous chloride tetrahydrate, 100-140 g / L of potassium chloride, 100-140 g / L of a coordination agent, 1.5-2.5 mL / L of a leveling agent, 1.5-2.5 mL / L of a brightening agent, 25-30 mL / L of an auxiliary agent and 25-35 g / L of a stabilizer are adopted, the pH value of a plating solution is 6-8, the temperature of a plating tank is 20-35 DEG C, the cathode current density is 0.5-1.5 A / dm < 2 >, and the cathode movement is 2-4 m / min. The surface of the prepared titanium alloy cadmium-plated iron alloy colored passivated sample piece is free of white rust after being subjected to an acetate fog test for 500 h according to the GB / T 10125-2021 standard, and a plating layer has excellent corrosion resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and in particular relates to a cyanide-free cadmium iron alloy plating process for aerospace titanium alloy parts. Background Art

[0002] Titanium is a silvery-white transition metal characterized by light weight, good mechanical properties, non-magnetic properties, and easy processing. Due to its stable chemical properties, good resistance to high and low temperatures, strong acid and alkali, and high specific strength, it is known as "space metal" and has been widely used in aerospace, petroleum, electricity, biomedicine and other fields. However, titanium alloys themselves have defects such as low hardness, poor wear resistance, easy adhesion, sensitivity to adhesive wear and fretting wear, and poor thermal and electrical conductivity, which limit the breadth and depth of their application to a certain extent.

[0003] In order to make titanium and titanium alloys play a greater role in aerospace and even other fields, they must be surface treated and a covering layer must be prepared on their surface to improve properties such as hardness and wear resistance. Methods to improve the surface properties of titanium and titanium alloys include electroplating, chemical plating, anodizing, micro-arc oxidation, ion implantation, thermal oxidation, laser cladding, and chemical and physical vapor deposition. Among them, electroplating and chemical plating are the most effective technical means. Electroplating and chemical plating can greatly improve the wear resistance of the surface of titanium and titanium alloys, and give them some new physical properties. The titanium alloy electroplating processes reported in the existing literature mainly include hard chromium plating, chemical nickel plating and electroless nickel plating, and the prepared coatings are all functional coatings. [1-3] At present, chemical nickel plating on the surface of titanium alloy has been applied in the aerospace field, realizing the functional transformation of the surface of titanium alloy.

[0004] Cyanide-free cadmium plating has excellent corrosion resistance and has been widely used in the aerospace field. [4] The performance of cadmium alloy plating is usually higher than that of single-component cadmium plating. Using cyanide-free cadmium alloy plating instead of cyanide-free cadmium plating can further improve the corrosion resistance and other properties of the plating.

[0005] The preparation of cyanide-free cadmium alloy coatings on titanium alloy parts is expected to achieve new breakthroughs in improving the service life of aerospace parts.

[0006] Since titanium alloy has a low potential, it is very easy to oxidize to form a dense oxide film. There is usually a dense natural oxide film on the surface of titanium alloy. This oxide film can be removed by sandblasting, degreasing, and acid etching, but it will regenerate instantly after being washed with water and exposed to air. It is difficult to deposit a coating with good bonding strength on this film, which brings great difficulties to titanium alloy electroplating. [5] Therefore, the pre-treatment process before plating must be solved before plating on titanium alloy. Traditional activation process research mainly focuses on the replacement oxide film method. [6]. This method is to remove the naturally formed oxide film on the titanium alloy substrate and replace it with a catalytically active film layer that is well bonded to the substrate, such as a zinc film, a hydrogenated film, and a fluorinated film, etc., to ensure that the titanium alloy substrate is not re-oxidized before electroplating, and then electroplating on this film layer. In the past, the zinc immersion method was widely used to immerse a layer of zinc on the substrate from which the oxide film was removed, and then plate other metals. At present, the surface activation of titanium alloys mainly adopts the mixed acid activation method, including nitric acid plus hydrochloric acid plus hydrofluoric acid activation, nitric acid plus hydrofluoric acid activation, and hydrochloric acid plus hydrofluoric acid activation. After activation, a fluorinated film is generated on the surface of the titanium alloy to prevent the regeneration of an oxide film on its surface.

[0007] References: [1]. Zhao Licai, Gao Jing, Sha Chunpeng, Double-layer chromium electroplating process on TC2 titanium alloy surface [J], Electroplating and Finishing, 2014, 33(21): 919-921. [2]. Tang Enjun, Zhao Yunqiang, Liu Zhi, et al., Study on the process of chemical Ni-P alloy plating on titanium alloy [J], Aviation Maintenance and Engineering, 2016, 61(10): 84-87. [3]. Zou Songhua, Wang Shuaidong, Li Man, et al., Nickel electroplating process and coating properties of TC4 titanium alloy [J], Electroplating and Finishing, 2016, 35(12): 626-628. [4]. Lai Huanwen, Guo Chongwu, Chen Mei, et al., Preparation of ultra-high corrosion resistance potassium chloride cadmium plating protective layer [J], Electroplating and Finishing, 2021, 40(23): 1762-1766. [5]. Zhang Ke, Liu Daoxin, Research on activation pretreatment process before wet plating of titanium alloy [J], Materials Protection, 2001, 34(10): 42-43. [6]. Feng Qiuyuan, Guo Jialin, Li Meng, et al., Research status and application of chromium electroplating on titanium alloy [J], Materials Protection, 2018, 51(10): 109-113. Summary of the invention

[0008] In order to expand the application scope of titanium alloy in the aerospace field, the present invention provides a cyanide-free cadmium iron alloy plating process for aerospace titanium alloy parts. In order to achieve the above purpose, the present invention adopts the following technical solutions: A cyanide-free cadmium iron alloy plating process for aerospace titanium alloy parts comprises the following steps: (1) Sandblasting and degreasing titanium alloy workpieces; (2) Titanium alloy workpieces are activated by hydrochloric acid pickling process after sandblasting and degreasing; (3) After the titanium alloy workpiece is pickled and activated, the impact nickel coating is prepared using the current impact nickel plating process; (4) After the titanium alloy workpiece is plated with impact nickel, a cyanide-free copper plating layer is prepared using a polymerized thiocyanate copper plating process; (5) After the titanium alloy workpiece is copper plated, a cyanide-free cadmium-iron alloy coating is prepared by a cyanide-free cadmium-iron alloy plating process; (6) the titanium alloy workpiece is plated with cadmium iron alloy and then post-processed to prepare a passivation layer; (7) After the titanium alloy workpiece is passivated, a graphene-modified sealing agent is used to prepare a graphene-modified sealing layer; The hydrochloric acid pickling process includes the following components, process parameters, and process requirements: Density: 1.18 g / cm 3 100~200mL / L of hydrochloric acid, operate at room temperature, pickling until large bubbles appear on the surface of the titanium alloy workpiece, and directly put it into the impact nickel plating tank for impact nickel plating without water washing after pickling activation; The cyanide-free cadmium iron alloy plating process includes the following components and process parameters: Cadmium chloride 25-35g / L, ferrous chloride tetrahydrate 4-6g / L, potassium chloride 100-140g / L, complexing agent 100-140g / L, leveling agent 1.5-2.5mL / L, brightener 1.5-2.5mL / L, auxiliary agent 25-30mL / L, stabilizer 25-35g / L, plating solution pH 6-8, plating tank temperature 20-35℃, cathode current density 0.5-1.5A / dm 2 , cathode moves 2-4 m / min; The leveling agent includes 5-10 g / L of trimercapto-s-triazine, 30-60 g / L of organic amine epoxy derivative with product model GDX, and 5-10 g / L of sodium hydroxide; The stabilizer includes sodium gluconate and sodium hydrogen succinate, and the mass ratio of sodium gluconate to sodium hydrogen succinate is 1:(2-3); The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid. The above components are mixed evenly to obtain the complexing agent; the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:(1-2):(4-6); The brightener comprises three components: A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate; wherein component A is 30-80 g / L, component B is 30-80 g / L, component C is 60-100 g / L, and isopropyl alcohol is 280-320 g / L; The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate composed of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; wherein the polyacrylamide with a molecular weight less than 8000 is 50-80 g / L, the condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin is 20-50 g / L, the sodium salt of 2-ethylhexyl sulfate is 30-80 g / L, and the D component is 30-60 g / L.

[0009] In some of the embodiments, the thickness of the cyanide-free cadmium iron coating is 8 to 15 μm.

[0010] In some embodiments, the polythiocyanate copper plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 18-24 g / L, polymeric sodium thiocyanate 130-170 g / L, sodium hydroxyethylidene diphosphonate 20-30 g / L, copper plating brightener 8-12 mL / L, plating solution pH 12-13, plating tank temperature 30-40 °C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of anode to cathode is >3:1, and the anode moves 3 to 5 m / min.

[0011] In some of the embodiments, the copper plating brightener comprises the following components in weight fractions: 60-100 parts of N,N'-di-n-propylethylenediamine, 10-20 parts of waterborne polyurethane resin, 80-120 parts of polyacrylamide with a molecular weight less than 8000, and 770-870 parts of deionized water.

[0012] In some embodiments, the thickness of the cyanide-free copper plating layer is 4-8 μm.

[0013] In some of the embodiments, the strike nickel plating layer is prepared by using the current strike nickel plating process.

[0014] In some of the embodiments, the passivation layer includes a hexavalent chromium color passivation layer, a hexavalent chromium military green passivation layer, a hexavalent chromium black passivation layer, and a hexavalent chromium olive drab passivation layer.

[0015] In some of the embodiments, the hexavalent chromium color passivation layer is prepared by HC-5 low chromium color passivation process: the volume concentration of HC-5 high protection low chromium color passivator is 2% to 4%, the passivation temperature is 20 to 35°C, the pH value of the passivation solution is 1.3 to 2.0, the passivation time is 5 to 15s, and weak air stirring or workpiece swinging is performed.

[0016] In some of the embodiments, the hexavalent chromium military green passivation layer is prepared using the OVG-31 military green passivation process: OVG-31 military green passivator 80-120 mL / L, passivation solution pH 1.0-1.6, passivation temperature 20-30°C, passivation time 30-90s, weak air stirring or swinging the plated piece.

[0017] In some of the embodiments, the hexavalent chromium black passivation layer is prepared by BZ-71 cadmium plating black passivation process: BZ-71A cadmium plating black passivation agent 80-100mL / L, BZ-71B cadmium plating black passivation agent 80-100mL / L, passivation solution pH 1.1-1.5, passivation temperature 20-35°C, passivation time 15-40s, weak air stirring or swinging the plated piece.

[0018] In some of the embodiments, the hexavalent chromium olive drab passivation layer is prepared by the UC-91 cadmium plating olive drab passivation process: chromic anhydride 25-45 g / L, phosphoric acid 8-16 ml / L, UC-91 activator 4-8 ml / L, UC-91 colorant 1-2 g / L, passivation temperature 20-28°C, passivation time 30-60 s, weak air stirring or swinging the workpiece.

[0019] In some embodiments, the graphene-modified sealing layer is prepared using a hydroxy graphene-modified sealing agent: (1) Dilute PRODICO 480 graphene-modified sealer with water to 2.5 to 3.2 times to prepare a sealing solution; (2) Immerse the passivated titanium alloy part in the sealing liquid for 8 to 15 seconds, drain it after exiting the tank, and blow away the sealing liquid remaining on the surface of the titanium alloy part with high-pressure air; (3) The sealed titanium alloy parts are dried and cured at 70 to 80° C. for 20 to 35 minutes.

[0020] In some of the embodiments, the thickness of the modified graphene sealing layer is 0.8-2.2 μm.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. The cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts of the present invention prepares a cadmium-iron alloy plating layer on a copper plating layer, and the cadmium-iron alloy plating layer is an anodic plating layer. This plating structure has an electrochemical protection effect and can effectively prevent the corrosive medium from corroding the titanium alloy substrate; 2. The cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts of the present invention has excellent corrosion resistance and can significantly improve the service life of titanium alloy parts; 3. The cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts of the present invention prepares a graphene-modified sealing layer on the passivation layer, which further improves the corrosion resistance of the cadmium-iron alloy coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is a schematic diagram of the coating structure of Example 1, Example 2, Example 3 and Example 4 of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0024] A cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts comprises the steps of sandblasting, degreasing, pickling and activating the titanium alloy workpiece, and sequentially preparing an impact nickel plating layer, a cyanide-free copper plating layer, a cyanide-free cadmium-iron alloy plating layer, a passivation layer, and a graphene-modified sealing layer on the titanium alloy substrate from the inside to the outside.

[0025] Titanium alloy pretreatment process is used to sandblast and degrease titanium alloy workpieces.

[0026] The titanium alloy parts are activated by the hydrochloric acid pickling process of the present invention after sandblasting and degreasing.

[0027] Preferably, the hydrochloric acid pickling process includes the following components, process parameters, and process requirements: Density: 1.18 g / cm 3 Use 100-200mL / L of hydrochloric acid and operate at room temperature. Pickling is carried out until large bubbles appear on the surface of the titanium alloy workpiece. After pickling and activation, it is directly put into the impact nickel plating tank for impact nickel plating without water washing.

[0028] The titanium alloy workpiece is pickled and activated, and then the impact nickel coating is prepared by the current impact nickel plating process.

[0029] Preferably, the strike nickel plating process includes the following components and process parameters: Nickel chloride hexahydrate 80~120g / L, hydrochloric acid 80~120g / L, normal temperature operation, cathode current density 3~6A / dm 2 , plating time is 2 to 6 minutes.

[0030] After the titanium alloy workpiece is plated with impact nickel, the polymerized thiocyanate copper plating process of the invention is adopted to prepare a cyanide-free copper plating layer.

[0031] Preferably, the thickness of the cyanide-free copper plating layer is 4 to 8 μm.

[0032] Preferably, the polythiocyanate copper plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 18-24 g / L, polymeric sodium thiocyanate 130-170 g / L, sodium hydroxyethylidene diphosphonate 20-30 g / L, copper plating brightener 8-12 mL / L, plating solution pH 12-13, plating tank temperature 30-40 °C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of anode to cathode is >3:1, and the anode moves 3 to 5 m / min.

[0033] Preferably, the copper plating brightener is prepared as follows: 770-870 parts of deionized water are added into a reaction tank, and 60-100 parts of N,N'-di-n-propylethylenediamine, 10-20 parts of waterborne polyurethane resin, and 80-120 parts of polyacrylamide with a molecular weight less than 8000 are added under stirring, and the brightener is obtained by stirring evenly.

[0034] After the titanium alloy workpiece is subjected to cyanide-free copper plating, the cyanide-free cadmium-iron alloy plating process of the invention is adopted to prepare a cyanide-free cadmium-iron alloy plating layer.

[0035] Preferably, the thickness of the cyanide-free cadmium iron alloy coating is 8 to 15 μm.

[0036] Preferably, the cyanide-free cadmium iron alloy plating process includes the following components and process parameters: Cadmium chloride 25-35g / L, ferrous chloride tetrahydrate 4-6g / L, potassium chloride 100-140g / L, complexing agent 100-140g / L, leveling agent 1.5-2.5mL / L, brightener 1.5-2.5mL / L, auxiliary agent 25-30mL / L, stabilizer 25-35g / L, plating solution pH 6-8, plating tank temperature 20-35℃, cathode current density 0.5-1.5A / dm 2 , the cathode moves 2 to 4 m / min.

[0037] Preferably, the leveling agent includes 5-10 g / L of trimercapto-s-triazine, 30-60 g / L of an organic amine epoxy derivative with a product model of GDX, and 5-10 g / L of sodium hydroxide.

[0038] Preferably, the stabilizer comprises sodium gluconate and sodium hydrogen succinate, and the mass ratio of sodium gluconate to sodium hydrogen succinate is 1:(2-3).

[0039] Preferably, the complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid, and the above components are mixed evenly to obtain the complexing agent; the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:(1-2):(4-6).

[0040] Preferably, the brightener comprises three components A, B and C, wherein component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate; wherein component A is 30-80 g / L, component B is 30-80 g / L, component C is 60-100 g / L, and isopropyl alcohol is 280-100 g / L.

[0041] Preferably, the auxiliary agent includes polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, and component D, and component D is consistent with component C in the brightener; wherein the polyacrylamide with a molecular weight less than 8000 is 50-80 g / L, the condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin is 20-50 g / L, the sodium salt of 2-ethylhexyl sulfate is 30-80 g / L, and the component D is 30-60 g / L.

[0042] After the titanium alloy workpiece is plated with cadmium iron alloy, a passivation layer is prepared by using the current cadmium plating post-treatment process. Preferably, the passivation layer includes a hexavalent chromium color passivation layer, a hexavalent chromium military green passivation layer, a hexavalent chromium black passivation layer, and a hexavalent chromium olive drab passivation layer.

[0043] Preferably, the hexavalent chromium color passivation layer is prepared by using the HC-5 low-chromium color passivation process: The volume concentration of HC-5 high protection low chrome color passivator is 2% to 4%, the passivation temperature is 20 to 35°C, the pH value of the passivation solution is 1.3 to 2.0, the passivation time is 5 to 15s, and weak air stirring or workpiece swing is used.

[0044] Preferably, the hexavalent chromium military green passivation layer is prepared by OVG-31 military green passivation process: OVG-31 military green passivator 80~120mL / L, passivation solution pH value 1.0~1.6, passivation temperature 20~30℃, passivation time 30~90s, weak air stirring or swinging the plated parts.

[0045] Preferably, the hexavalent chromium black passivation layer is prepared by using the BZ-71 cadmium plating black passivation process: BZ-71A cadmium black passivation agent 80~100mL / L, BZ-71B cadmium black passivation agent 80~100mL / L, passivation solution pH value 1.1~1.5, passivation temperature 20~35℃, passivation time 15~40s, weak air stirring or swinging the plated parts.

[0046] Preferably, the hexavalent chromium olive-drab passivation layer is prepared by using the UC-91 cadmium plating olive-drab passivation process: Chromic anhydride 25-45g / L, phosphoric acid 8-16ml / L, UC-91 activator 4-8ml / L, UC-91 colorant 1-2g / L, passivation temperature 20-28℃, passivation time 30-60s, weak air stirring or swinging the workpiece.

[0047] After the titanium alloy workpiece is passivated, the graphene modified sealing layer is prepared using the PRODICO 480 graphene sealing process of Chaobang Chemical.

[0048] Preferably, the thickness of the graphene modified sealing layer is 0.8 to 2.2 μm.

[0049] Preferably, the PRODICO 480 graphene sealing process includes the following steps, ingredients, and process parameters: (1) Dilute PRODICO 480 graphene-modified sealant with water to 2.5 to 3.2 times to prepare a sealing solution; (2) Immerse the passivated titanium alloy part in the sealing liquid for 8 to 15 seconds, drain it after exiting the tank, and blow off the sealing liquid remaining on the surface of the titanium alloy part with high-pressure air; (3) The sealed titanium alloy parts are dried and cured at 70 to 80° C. for 20 to 35 minutes.

[0050] Embodiment 1: A cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts comprises the following steps: sandblasting, degreasing, pickling activation, impact nickel plating, cyanide-free copper plating, cyanide-free cadmium-iron alloy plating, passivation, and sealing on a titanium alloy substrate.

[0051] like Figure 1 As shown, the coating structure prepared by the cyanide-free cadmium-iron alloy plating process includes a titanium alloy substrate 1, and an impact nickel plating layer 2, a cyanide-free copper plating layer 3, a cyanide-free cadmium-iron alloy plating layer 4, a hexavalent chromium color passivation layer 5, and a graphene modified sealing layer 6 are prepared on the titanium alloy substrate 1 from the inside to the outside.

[0052] 1. Pre-treatment: 1) Sand blasting and degreasing: The titanium alloy workpiece substrate 1 is sandblasted and degreased using the current titanium alloy pretreatment process.

[0053] 2) Pickling activation: After sandblasting and degreasing, the titanium alloy workpiece substrate 1 is activated by the titanium alloy pickling activation process of the present invention. The pickling activation process and requirements are as follows: Density: 1.18 g / cm 3 Use 150mL / L hydrochloric acid and operate at room temperature. Pickling is carried out until large bubbles appear on the surface of the titanium alloy workpiece. After pickling and activation, it is directly put into the impact nickel plating tank for impact nickel plating without water washing.

[0054] 2. Impact nickel plating: After pickling and activation, the titanium alloy workpiece is subjected to the following impact nickel plating process to prepare the impact nickel coating 2.

[0055] Nickel chloride hexahydrate 100g / L, hydrochloric acid 100g / L, room temperature operation, cathode current density 5A / dm 2 , plating time 4min.

[0056] 3. Cyanide-free copper plating: After the titanium alloy workpiece is plated with impact nickel, the polymerized thiocyanate copper plating process of the present invention is used to prepare a cyanide-free copper plating layer 3, and the thickness of the copper plating layer is 6 μm.

[0057] 1) Preparation of copper plating brightener: Calculated by weight, 820 parts of deionized water were added to a reaction tank, and 80 parts of N,N'-di-n-propylethylenediamine, 15 parts of waterborne polyurethane resin, and 100 parts of polyacrylamide with a molecular weight less than 8000 were added under stirring, and stirred evenly to obtain the brightener.

[0058] 2) Plating: Polycuprous thiocyanate 21g / L, sodium polythiocyanate 150g / L, sodium hydroxyethylidene diphosphonate 25g / L, copper plating brightener 10mL / L, plating solution pH 12.5, plating tank temperature 35℃, cathode current density 1.0A / dm 2 , the cathode moves 4m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of anode to cathode is >3:1, and the anode moves 4m / min.

[0059] 4. Cadmium-plated iron alloy: After the titanium alloy workpiece is subjected to cyanide-free copper plating, the cyanide-free cadmium-iron alloy plating process of the present invention is adopted to prepare a cyanide-free cadmium-iron alloy coating 4, and the thickness of the cadmium-iron alloy coating is 12 μm.

[0060] 1) Preparation of leveling agent: The leveling agent includes 7.5 g / L of trimercapto-s-triazine, 45 g / L of an organic amine epoxy derivative with a product model of GDX sold by Sefik New Materials Co., Ltd., and 7.5 g / L of sodium hydroxide. According to the formula requirements, sodium hydroxide is dissolved in water, and trimercapto-s-triazine is added, stirred to dissolve, and then the organic amine epoxy derivative is added, and water is added to the required volume to obtain the leveling agent.

[0061] 2) Preparation of stabilizer: The stabilizer includes sodium glucoheptanoate and sodium hydrogen succinate, and the mass ratio of sodium glucoheptanoate to sodium hydrogen succinate is 1:2.5. Sodium glucoheptanoate and sodium hydrogen succinate are mixed together according to the formula ratio requirements, and stirred evenly to obtain the stabilizer.

[0062] 3) Preparation of complexing agent: The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid, and the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:1.5:5. Nitrilotriacetic acid, sulfosalicylic acid, and malic acid are mixed together according to the formula ratio and stirred evenly to obtain the complexing agent.

[0063] 4) Prepare brightener: The brightener comprises three components: A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate. 30kg of isopropanol is added to 40kg of water and mixed evenly, 5.5kg of component A, 4kg of component B and 8kg of component C are added, stirred to dissolve, and water is added to 100L to obtain the brightener.

[0064] 5) Preparation of auxiliary agents: The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; 6.5 kg of polyacrylamide with a molecular weight less than 8000, 3.5 kg of a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, 5.5 kg of sodium salt of 2-ethylhexyl sulfate, and 4.5 kg of the D component are added to 70 kg of water, stirred to dissolve, and water is added to 100 L to obtain the auxiliary agent.

[0065] 6) Plating: Cadmium chloride 30g / L, ferrous chloride tetrahydrate 5g / L, potassium chloride 120g / L, complexing agent 120g / L, leveling agent 2.0mL / L, brightener 2.0mL / L, auxiliary agent 27mL / L, stabilizer 30g / L, plating solution pH 7, plating tank temperature 28℃, cathode current density 1.0A / dm 2 , cathode moves 3m / min.

[0066] 5. Hexavalent chromium color passivation: After the titanium alloy workpiece is plated with cadmium iron alloy, the hexavalent chromium color passivation layer 5 is prepared using the HC-5 low chromium color passivation process of Chaobang Chemical.

[0067] The volume concentration of HC-5 high protection low chrome color passivator is 3%, the passivation temperature is 28℃, the pH of the passivation solution is 1.6, the passivation time is 8s, and the workpiece swings.

[0068] The specific process is "lightening with 1.5% volume fraction nitric acid → water washing → passivation → water washing → draining after leaving the tank".

[0069] 6. Closure: After the titanium alloy workpiece is passivated, the graphene modified sealing layer 6 is prepared by using the PRODICO 480 graphene sealing process of Chaobang Chemical, and the thickness of the sealing layer is 1.5 μm.

[0070] Preferably, the PRODICO 480 graphene sealing process includes the following steps and process parameters: 1) Dilute PRODICO 480 graphene-modified sealer with water to 2.8 times to prepare the sealing solution; 2) Immerse the passivated titanium alloy parts in the sealing liquid for 10 seconds, drain them after exiting the tank, and use high-pressure air to blow away the sealing liquid remaining on the surface of the titanium alloy parts; 3) Dry and cure the sealed titanium alloy parts at 75°C for 30 minutes.

[0071] Embodiment 2: A cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts comprises the following steps: sandblasting, degreasing, pickling activation, impact nickel plating, cyanide-free copper plating, cyanide-free cadmium-iron alloy plating, passivation, and sealing on a titanium alloy substrate.

[0072] like Figure 1 As shown, the coating structure prepared by the cyanide-free cadmium-iron alloy plating process includes a titanium alloy substrate 1, and an impact nickel plating layer 2, a cyanide-free copper plating layer 3, a cyanide-free cadmium-iron alloy plating layer 4, a hexavalent chromium military green passivation layer 5, and a graphene-modified sealing layer 6 are prepared on the titanium alloy substrate 1 from the inside to the outside.

[0073] 1. Pre-treatment: 1) Sand blasting and degreasing: The titanium alloy workpiece substrate 1 is sandblasted and degreased using the current titanium alloy pretreatment process.

[0074] 2) Pickling activation: After sandblasting and degreasing, the titanium alloy workpiece substrate 1 is activated by the titanium alloy pickling activation process of the present invention. The pickling activation process and requirements are as follows: Density: 1.18 g / cm 3 Use 200mL / L hydrochloric acid and operate at room temperature. Pickling is carried out until large bubbles appear on the surface of the titanium alloy workpiece. After pickling and activation, it is directly put into the impact nickel plating tank for impact nickel plating without water washing.

[0075] 2. Impact nickel plating: After pickling and activation, the titanium alloy workpiece is subjected to the following impact nickel plating process to prepare the impact nickel coating 2.

[0076] Nickel chloride hexahydrate 120g / L, hydrochloric acid 120g / L, room temperature operation, cathode current density 5A / dm 2 , plating time 4min.

[0077] 3. Cyanide-free copper plating: After the titanium alloy workpiece is plated with impact nickel, the polymerized thiocyanate copper plating process of the present invention is used to prepare a cyanide-free copper plating layer 3, and the thickness of the copper plating layer is 6 μm.

[0078] 1) Preparation of copper plating brightener: Calculated by weight, 820 parts of deionized water were added to a reaction tank, and 80 parts of N,N'-di-n-propylethylenediamine, 15 parts of waterborne polyurethane resin, and 100 parts of polyacrylamide with a molecular weight less than 8000 were added under stirring, and stirred evenly to obtain the brightener.

[0079] 2) Plating: Polycuprous thiocyanate 24g / L, polysodium thiocyanate 170g / L, sodium hydroxyethylidene diphosphonate 25g / L, copper plating brightener 10mL / L, plating solution pH 12.5, plating tank temperature 30℃, cathode current density 1.0A / dm 2 , the cathode moves 4m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of anode to cathode is >3:1, and the anode moves 4m / min.

[0080] 4. Cadmium-plated iron alloy: After the titanium alloy workpiece is subjected to cyanide-free copper plating, the cyanide-free cadmium-iron alloy plating process of the present invention is adopted to prepare a cyanide-free cadmium-iron alloy coating 4, and the thickness of the cadmium-iron alloy coating is 12 μm.

[0081] 1) Preparation of leveling agent: The leveling agent includes 7.5 g / L of trimercapto-s-triazine, 45 g / L of an organic amine epoxy derivative with a product model of GDX sold by Sefik New Materials Co., Ltd., and 7.5 g / L of sodium hydroxide. According to the formula requirements, sodium hydroxide is dissolved in water, and trimercapto-s-triazine is added, stirred to dissolve, and then the organic amine epoxy derivative is added, and water is added to the required volume to obtain the leveling agent.

[0082] 2) Preparation of stabilizer: The stabilizer includes sodium glucoheptanoate and sodium hydrogen succinate, and the mass ratio of sodium glucoheptanoate to sodium hydrogen succinate is 1:2.5. Sodium glucoheptanoate and sodium hydrogen succinate are mixed together according to the formula ratio requirements, and stirred evenly to obtain the stabilizer.

[0083] 3) Preparation of complexing agent: The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid, and the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:1.5:5. Nitrilotriacetic acid, sulfosalicylic acid, and malic acid are mixed together according to the formula ratio and stirred evenly to obtain the complexing agent.

[0084] 4) Prepare brightener: The brightener comprises three components: A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate. 30kg of isopropanol is added to 40kg of water and mixed evenly, 5.5kg of component A, 4kg of component B and 8kg of component C are added, stirred to dissolve, and water is added to 100L to obtain the brightener.

[0085] 5) Preparation of auxiliary agents: The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; 6.5 kg of polyacrylamide with a molecular weight less than 8000, 3.5 kg of a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, 5.5 kg of sodium salt of 2-ethylhexyl sulfate, and 4.5 kg of the D component are added to 70 kg of water, stirred to dissolve, and water is added to 100 L to obtain the auxiliary agent.

[0086] 6) Plating: Cadmium chloride 28g / L, ferrous chloride tetrahydrate 4.7g / L, potassium chloride 135g / L, complexing agent 125g / L, leveling agent 2.0mL / L, brightener 2.0mL / L, auxiliary agent 28mL / L, stabilizer 28g / L, plating solution pH 6.5, plating tank temperature 32℃, cathode current density 1.0A / dm 2 , cathode moves 3m / min.

[0087] 6. Hexavalent chromium military green passivation: After the titanium alloy workpiece is plated with cadmium iron alloy, the military green passivation layer 5 is prepared using Chaobang Chemical's OVG-31 military green passivation process.

[0088] OVG-31 military green passivator 100mL / L, passivation solution pH 1.3, passivation temperature 25℃, passivation time 60s, swing plated parts.

[0089] The specific process is "lightening with 1.5% volume fraction nitric acid → water washing → passivation → water washing → draining after leaving the tank".

[0090] 6. Closure: After the titanium alloy workpiece is passivated, the graphene modified sealing layer 6 is prepared by using the PRODICO 480 graphene sealing process of Chaobang Chemical, and the thickness of the sealing layer is 1.5 μm.

[0091] The PRODICO 480 graphene sealing process includes the following steps and process parameters: 1) Dilute PRODICO 480 graphene-modified sealer with water to 2.8 times to prepare the sealing solution; 2) Immerse the passivated titanium alloy parts in the sealing liquid for 10 seconds, drain them after exiting the tank, and use high-pressure air to blow away the sealing liquid remaining on the surface of the titanium alloy parts; 3) Dry and cure the sealed titanium alloy parts at 80°C for 20 minutes.

[0092] Embodiment 3: A cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts comprises the following steps: sandblasting, degreasing, pickling activation, impact nickel plating, cyanide-free copper plating, cyanide-free cadmium-iron alloy plating, passivation, and sealing on a titanium alloy substrate.

[0093] like Figure 1 As shown, the coating structure prepared by the cyanide-free cadmium-iron alloy plating process includes a titanium alloy substrate 1, and an impact nickel plating layer 2, a cyanide-free copper plating layer 3, a cyanide-free cadmium-iron alloy plating layer 4, a hexavalent chromium black passivation layer 5, and a graphene-modified sealing layer 6 are prepared on the titanium alloy substrate 1 from the inside to the outside.

[0094] 1. Pre-treatment: 1) Sand blasting and degreasing: The titanium alloy workpiece substrate 1 is sandblasted and degreased using the current titanium alloy pretreatment process.

[0095] 2) Pickling activation: After sandblasting and degreasing, the titanium alloy workpiece substrate 1 is activated by the titanium alloy pickling activation process of the present invention. The pickling activation process and requirements are as follows: Density: 1.18 g / cm 3 Add 100mL / L hydrochloric acid and operate at room temperature. Pickling until large bubbles appear on the surface of the titanium alloy workpiece. After pickling and activation, it is directly put into the impact nickel plating tank for impact nickel plating without water washing.

[0096] 2. Impact nickel plating: After pickling and activation, the titanium alloy workpiece is subjected to the following impact nickel plating process to prepare the impact nickel coating 2.

[0097] Nickel chloride hexahydrate 80g / L, hydrochloric acid 80g / L, room temperature operation, cathode current density 5A / dm 2 , plating time 4min.

[0098] 3. Cyanide-free copper plating: After the titanium alloy workpiece is plated with impact nickel, the polymerized thiocyanate copper plating process of the present invention is used to prepare a cyanide-free copper plating layer 3, and the thickness of the copper plating layer is 6 μm.

[0099] 1) Preparation of copper plating brightener: Calculated by weight, 820 parts of deionized water were added to a reaction tank, and 80 parts of N,N'-di-n-propylethylenediamine, 15 parts of waterborne polyurethane resin, and 100 parts of polyacrylamide with a molecular weight less than 8000 were added under stirring, and stirred evenly to obtain the brightener.

[0100] 2) Plating: Polycuprous thiocyanate 18g / L, sodium polythiocyanate 130g / L, sodium hydroxyethylidene diphosphonate 25g / L, copper plating brightener 10mL / L, plating solution pH 13, plating tank temperature 40℃, cathode current density 1.0A / dm 2 , the cathode moves 4m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of anode to cathode is >3:1, and the anode moves 4m / min.

[0101] 4. Cadmium-plated iron alloy: After the titanium alloy workpiece is subjected to cyanide-free copper plating, the cyanide-free cadmium-iron alloy plating process of the present invention is adopted to prepare a cyanide-free cadmium-iron alloy coating 4, and the thickness of the cadmium-iron alloy coating is 12 μm.

[0102] 1) Preparation of leveling agent: The leveling agent includes 7.5 g / L of trimercapto-s-triazine, 45 g / L of an organic amine epoxy derivative with a product model of GDX sold by Sefik New Materials Co., Ltd., and 7.5 g / L of sodium hydroxide. According to the formula requirements, sodium hydroxide is dissolved in water, and trimercapto-s-triazine is added, stirred to dissolve, and then the organic amine epoxy derivative is added, and water is added to the required volume to obtain the leveling agent.

[0103] 2) Preparation of stabilizer: The stabilizer includes sodium glucoheptanoate and sodium hydrogen succinate, and the mass ratio of sodium glucoheptanoate to sodium hydrogen succinate is 1:2.5. Sodium glucoheptanoate and sodium hydrogen succinate are mixed together according to the formula ratio requirements, and stirred evenly to obtain the stabilizer.

[0104] 3) Preparation of complexing agent: The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid, and the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:1.5:5. Nitrilotriacetic acid, sulfosalicylic acid, and malic acid are mixed together according to the formula ratio and stirred evenly to obtain the complexing agent.

[0105] 4) Prepare brightener: The brightener comprises three components: A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate. 30kg of isopropanol is added to 40kg of water and mixed evenly, 5.5kg of component A, 4kg of component B and 8kg of component C are added, stirred to dissolve, and water is added to 100L to obtain the brightener.

[0106] 5) Preparation of auxiliary agents: The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; 6.5 kg of polyacrylamide with a molecular weight less than 8000, 3.5 kg of a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, 5.5 kg of sodium salt of 2-ethylhexyl sulfate, and 4.5 kg of the D component are added to 70 kg of water, stirred to dissolve, and water is added to 100 L to obtain the auxiliary agent.

[0107] 6) Plating: Cadmium chloride 35g / L, ferrous chloride tetrahydrate 6g / L, potassium chloride 140g / L, complexing agent 140g / L, leveling agent 2.0mL / L, brightener 2.0mL / L, auxiliary agent 28mL / L, stabilizer 35g / L, plating solution pH 7.5, plating tank temperature 20℃, cathode current density 1.0A / dm 2 , cathode moves 3m / min.

[0108] 6. Hexavalent chromium black passivation: After the titanium alloy workpiece is plated with cadmium iron alloy, the hexavalent chromium black passivation layer 5 is prepared using the BZ-71 cadmium black passivation process of Chaobang Chemical.

[0109] BZ-71A cadmium black passivation agent 90mL / L, BZ-71B cadmium black passivation agent 90mL / L, passivation solution pH 1.3, passivation temperature 25℃, passivation time 28s, swing plated parts.

[0110] The specific process is "lightening with 1.5% volume fraction nitric acid → water washing → passivation → water washing → draining after leaving the tank".

[0111] 6. Closure: After the titanium alloy workpiece is passivated, the graphene modified sealing layer 6 is prepared by using the PRODICO 480 graphene sealing process of Chaobang Chemical, and the thickness of the sealing layer is 1.5 μm.

[0112] The PRODICO 480 graphene sealing process includes the following steps and process parameters: 1) Dilute PRODICO 480 graphene-modified sealer with water to 2.8 times to prepare the sealing solution; 2) Immerse the passivated titanium alloy parts in the sealing liquid for 10 seconds, drain them after exiting the tank, and use high-pressure air to blow away the sealing liquid remaining on the surface of the titanium alloy parts; 3) Dry and cure the sealed titanium alloy parts at 70°C for 35 minutes.

[0113] Embodiment 4: A cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts comprises the following steps: sandblasting, degreasing, pickling activation, impact nickel plating, cyanide-free copper plating, cyanide-free cadmium-iron alloy plating, passivation, and sealing on a titanium alloy substrate.

[0114] like Figure 1 As shown, the coating structure prepared by the cyanide-free cadmium-iron alloy plating process includes a titanium alloy substrate 1, and an impact nickel plating layer 2, a cyanide-free copper plating layer 3, a cyanide-free cadmium-iron alloy plating layer, a hexavalent chromium olive-drab passivation layer 5, and a graphene-modified sealing layer 6 are prepared on the titanium alloy substrate 1 from the inside to the outside.

[0115] 1. Pre-treatment: 1) Sand blasting and degreasing: The titanium alloy workpiece substrate 1 is sandblasted and degreased using the current titanium alloy pretreatment process.

[0116] 2) Pickling activation: After sandblasting and degreasing, the titanium alloy workpiece substrate 1 is activated by the titanium alloy pickling activation process of the present invention. The pickling activation process and requirements are as follows: Density: 1.18 g / cm 3 Use 130mL / L of hydrochloric acid and operate at room temperature. Pickling is carried out until large bubbles appear on the surface of the titanium alloy workpiece. After pickling and activation, it is directly put into the impact nickel plating tank for impact nickel plating without water washing.

[0117] 2. Impact nickel plating: After pickling and activation, the titanium alloy workpiece is subjected to the following impact nickel plating process to prepare the impact nickel coating 2.

[0118] Nickel chloride hexahydrate 90g / L, hydrochloric acid 90g / L, room temperature operation, cathode current density 5A / dm 2 , plating time 4min.

[0119] 3. Cyanide-free copper plating: After the titanium alloy workpiece is plated with impact nickel, the polymerized thiocyanate copper plating process of the present invention is used to prepare a cyanide-free copper plating layer 3, and the thickness of the copper plating layer is 6 μm.

[0120] 1) Preparation of copper plating brightener: Calculated by weight, 820 parts of deionized water were added to a reaction tank, and 80 parts of N,N'-di-n-propylethylenediamine, 15 parts of waterborne polyurethane resin, and 100 parts of polyacrylamide with a molecular weight less than 8000 were added under stirring, and stirred evenly to obtain the brightener.

[0121] 2) Plating: Polycuprous thiocyanate 23g / L, polysodium thiocyanate 165g / L, sodium hydroxyethylidene diphosphonate 25g / L, copper plating brightener 10mL / L, plating solution pH 12.8, plating tank temperature 32℃, cathode current density 1.0A / dm 2 , the cathode moves 4m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of anode to cathode is >3:1, and the anode moves 4m / min.

[0122] 4. Cadmium-plated iron alloy: After the titanium alloy workpiece is subjected to cyanide-free copper plating, the cyanide-free cadmium-iron alloy plating process of the present invention is adopted to prepare a cyanide-free cadmium-iron alloy coating 4, and the thickness of the cadmium-iron alloy coating is 12 μm.

[0123] 1) Preparation of leveling agent: The leveling agent includes 7.5 g / L of trimercapto-s-triazine, 45 g / L of an organic amine epoxy derivative with a product model of GDX sold by Sefik New Materials Co., Ltd., and 7.5 g / L of sodium hydroxide. According to the formula requirements, sodium hydroxide is dissolved in water, and trimercapto-s-triazine is added, stirred to dissolve, and then the organic amine epoxy derivative is added, and water is added to the required volume to obtain the leveling agent.

[0124] 2) Preparation of stabilizer: The stabilizer includes sodium glucoheptanoate and sodium hydrogen succinate, and the mass ratio of sodium glucoheptanoate to sodium hydrogen succinate is 1:2.5. Sodium glucoheptanoate and sodium hydrogen succinate are mixed together according to the formula ratio requirements, and stirred evenly to obtain the stabilizer.

[0125] 3) Preparation of complexing agent: The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid, and the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:1.5:5. Nitrilotriacetic acid, sulfosalicylic acid, and malic acid are mixed together according to the formula ratio and stirred evenly to obtain the complexing agent.

[0126] 4) Prepare brightener: The brightener comprises three components: A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate. 30kg of isopropanol is added to 40kg of water and mixed evenly, 5.5kg of component A, 4kg of component B and 8kg of component C are added, stirred to dissolve, and water is added to 100L to obtain the brightener.

[0127] 5) Preparation of auxiliary agents: The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; 6.5 kg of polyacrylamide with a molecular weight less than 8000, 3.5 kg of a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, 5.5 kg of sodium salt of 2-ethylhexyl sulfate, and 4.5 kg of the D component are added to 70 kg of water, stirred to dissolve, and water is added to 100 L to obtain the auxiliary agent.

[0128] 6) Plating: Cadmium chloride 25g / L, ferrous chloride tetrahydrate 4g / L, potassium chloride 140g / L, complexing agent 100g / L, leveling agent 2.0mL / L, brightener 2.0mL / L, auxiliary agent 28mL / L, stabilizer 25g / L, plating solution pH 8, plating tank temperature 30℃, cathode current density 1.0A / dm 2 , cathode moves 3m / min.

[0129] 6. Hexavalent chromium olive color passivation: After the titanium alloy workpiece is plated with cadmium iron alloy, the hexavalent chromium olive-drab passivation layer 6 is prepared by using the UC-91 cadmium hexavalent chromium olive-drab passivation process of Chaobang Chemical.

[0130] Chromic anhydride 30g / L, phosphoric acid 12ml / L, UC-91 activator 6ml / L, UC-91 colorant 1.5g / L, passivation temperature 25℃, passivation time 45s, swing the workpiece.

[0131] The specific process is "lightening with 1.5% volume fraction nitric acid → water washing → passivation → water washing → draining after leaving the tank".

[0132] 6. Closure: After the titanium alloy workpiece is passivated, the graphene modified sealing layer 6 is prepared by using the PRODICO 480 graphene sealing process of Chaobang Chemical, and the thickness of the sealing layer is 1.5 μm.

[0133] Preferably, the PRODICO 480 graphene sealing process includes the following steps and process parameters: (1) Dilute PRODICO 480 graphene-modified sealer with water to 2.8 times to prepare a sealing solution; (2) Immerse the passivated titanium alloy part in the sealing liquid for 12 seconds, drain it after exiting the tank, and blow away the sealing liquid remaining on the surface of the titanium alloy part with high-pressure air; (3) The sealed titanium alloy parts are dried and cured at 78°C for 28 minutes.

[0134] Test Example 1: According to GB / T 10125-2021 "Artificial atmosphere corrosion test salt spray test", the acetic acid salt spray test was carried out. The titanium alloy cadmium iron alloy hexavalent chromium color passivation sample prepared in Example 1 had no white rust on the surface after 500 hours, the titanium alloy cadmium iron alloy hexavalent chromium military green passivation sample prepared in Example 2 had no white rust on the surface after 528 hours, the titanium alloy cadmium iron alloy hexavalent chromium black passivation sample prepared in Example 3 had no white rust on the surface after 480 hours, and the titanium alloy cadmium iron alloy hexavalent chromium olive drab passivation sample prepared in Example 4 had no white rust on the surface after 500 hours. The prepared coatings have excellent corrosion resistance.

[0135] Test Example 2: The titanium alloy cadmium-plated iron alloy samples prepared in Example 1, Example 2, Example 3, and Example 4 were tested for coating adhesion in accordance with GB / T 5270-2005 "Review of test methods for adhesion strength of electrodeposited and chemically deposited metal coatings on metal substrates". The samples were placed in a heating furnace and heated to 250°C for 30 minutes. After being taken out, they were immediately placed in room temperature water for cooling. There was no blistering or shedding of the coating, and the coating adhesion met the standard requirements.

[0136] Test Example 3: The titanium alloy cadmium-plated iron alloy samples prepared in Example 1, Example 2, Example 3, and Example 4 were tested for 360 hours at a temperature of 40°C and a relative humidity of 93% in accordance with GB / T 2423.3-2016 "Basic Environmental Test Procedures for Electrical and Electronic Products Test Ca: Steady State Wet Heat Test Method". There was no visible change in the coating, meeting the technical requirements of the industry.

[0137] Test example 4: The titanium alloy cadmium-plated iron alloy samples prepared in Example 1, Example 2, Example 3, and Example 4 were subjected to a mold test for 28 days in accordance with GJB150.9A-2009 "Military Equipment Laboratory Environmental Test Method Part 10: Mold Test". No mold grew on the surface of the samples, which met the requirements of industry standards.

[0138] The technical solutions provided by the embodiments of the present invention are described in detail above. The principles and implementation methods of the embodiments of the present invention are described in detail using specific examples herein. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which are also considered to fall within the protection scope of the present invention.

Claims

1. A cyanide-free cadmium iron alloy plating process for aerospace titanium alloy parts, characterized in that: The following steps are involved: (1) Sandblasting and degreasing titanium alloy workpieces; (2) Titanium alloy workpieces are activated by hydrochloric acid pickling process after sandblasting and degreasing; (3) After the titanium alloy workpiece is pickled and activated, the impact nickel coating is prepared using the current impact nickel plating process; (4) After the titanium alloy workpiece is plated with impact nickel, a cyanide-free copper plating layer is prepared using a polymerized thiocyanate copper plating process; (5) After the titanium alloy workpiece is copper plated, a cyanide-free cadmium-iron alloy coating is prepared by a cyanide-free cadmium-iron alloy plating process; (6) the titanium alloy workpiece is plated with cadmium iron alloy and then post-processed to prepare a passivation layer; (7) After the titanium alloy workpiece is passivated, a graphene-modified sealing agent is used to prepare a graphene-modified sealing layer; The hydrochloric acid pickling process includes the following components, process parameters, and process requirements: Density: 1.18 g / cm 3 100~200mL / L of hydrochloric acid, operate at room temperature, pickling until large bubbles appear on the surface of the titanium alloy workpiece, and directly put it into the impact nickel plating tank for impact nickel plating without water washing after pickling activation; The cyanide-free cadmium iron alloy plating process includes the following components and process parameters: Cadmium chloride 25-35g / L, ferrous chloride tetrahydrate 4-6g / L, potassium chloride 100-140g / L, complexing agent 100-140g / L, leveling agent 1.5-2.5mL / L, brightener 1.5-2.5mL / L, auxiliary agent 25-30mL / L, stabilizer 25-35g / L, plating solution pH 6-8, plating tank temperature 20-35℃, cathode current density 0.5-1.5A / dm 2 , cathode moves 2-4 m / min; The leveling agent includes 5-10 g / L of trimercapto-s-triazine, 30-60 g / L of organic amine epoxy derivative with product model GDX, and 5-10 g / L of sodium hydroxide; The stabilizer includes sodium gluconate and sodium hydrogen succinate, and the mass ratio of sodium gluconate to sodium hydrogen succinate is 1:(2-3); The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid. The above components are mixed evenly to obtain the complexing agent; the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:(1-2):(4-6); The brightener comprises three components: A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate; wherein component A is 30-80 g / L, component B is 30-80 g / L, component C is 60-100 g / L, and isopropyl alcohol is 280-320 g / L; The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate composed of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; wherein the polyacrylamide with a molecular weight less than 8000 is 50-80 g / L, the condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin is 20-50 g / L, the sodium salt of 2-ethylhexyl sulfate is 30-80 g / L, and the D component is 30-60 g / L.

2. The cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts according to claim 1 is characterized in that: The thickness of the cyanide-free cadmium iron plating layer is 8 to 15 μm.

3. The cyanide-free cadmium iron alloy plating process for aerospace titanium alloy parts according to claim 1 is characterized in that: The polymerized thiocyanate copper plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 18-24 g / L, polymeric sodium thiocyanate 130-170 g / L, sodium hydroxyethylidene diphosphonate 20-30 g / L, copper plating brightener 8-12 mL / L, plating solution pH 12-13, plating tank temperature 30-40 °C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of anode to cathode is >3:1, and the anode moves 3 to 5 m / min.

4. The cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts according to claim 3 is characterized in that: The copper plating brightener comprises the following components in weight fractions: 60-100 parts of N,N'-di-n-propylethylenediamine, 10-20 parts of waterborne polyurethane resin, 80-120 parts of polyacrylamide with a molecular weight less than 8000, and 770-870 parts of deionized water.

5. The cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts according to claim 1 or 3, characterized in that: The thickness of the cyanide-free copper plating layer is 4 to 8 μm.

6. The cyanide-free cadmium iron alloy plating process for aerospace titanium alloy parts according to claim 1, characterized in that: The strike nickel plating layer is prepared by adopting the current strike nickel plating process.

7. The cyanide-free cadmium iron alloy plating process for aerospace titanium alloy parts according to claim 1, characterized in that: The passivation layer includes a hexavalent chromium color passivation layer, a hexavalent chromium military green passivation layer, a hexavalent chromium black passivation layer, and a hexavalent chromium olive drab passivation layer.

8. The cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts according to claim 7, characterized in that: The hexavalent chromium color passivation layer is prepared by HC-5 low-chromium color passivation process: the volume concentration of HC-5 high-protection low-chromium color passivator is 2% to 4%, the passivation temperature is 20 to 35° C., the pH value of the passivation solution is 1.3 to 2.0, the passivation time is 5 to 15 seconds, and weak air stirring or workpiece swinging is performed; The hexavalent chromium military green passivation layer is prepared by OVG-31 military green passivation process: OVG-31 military green passivation agent 80-120 mL / L, passivation solution pH value 1.0-1.6, passivation temperature 20-30° C., passivation time 30-90 s, weak air stirring or swinging the plated piece; The hexavalent chromium black passivation layer is prepared by using the BZ-71 cadmium black passivation process: BZ-71A cadmium black passivation agent 80-100mL / L, BZ-71B cadmium black passivation agent 80-100mL / L, passivation solution pH value 1.1-1.5, passivation temperature 20-35°C, passivation time 15-40s, weak air stirring or swinging the plated piece; The hexavalent chromium olive-drab passivation layer is prepared by the UC-91 cadmium plating olive-drab passivation process: chromic anhydride 25-45 g / L, phosphoric acid 8-16 ml / L, UC-91 activator 4-8 ml / L, UC-91 colorant 1-2 g / L, passivation temperature 20-28° C., passivation time 30-60 s, weak air stirring or swinging the workpiece.

9. The cyanide-free cadmium iron alloy plating process for aerospace titanium alloy parts according to claim 1, characterized in that: The graphene-modified sealing layer is prepared by using a hydroxy graphene-modified sealing agent: (1) Dilute PRODICO 480 graphene-modified sealer with water to 2.5 to 3.2 times to prepare a sealing solution; (2) Immerse the passivated titanium alloy part in the sealing liquid for 8 to 15 seconds, drain it after exiting the tank, and blow away the sealing liquid remaining on the surface of the titanium alloy part with high-pressure air; (3) The sealed titanium alloy parts are dried and cured at 70 to 80° C. for 20 to 35 minutes.

10. The cyanide-free cadmium-iron alloy plating process for aerospace titanium alloy parts according to claim 1 or 9, characterized in that: The thickness of the modified graphene sealing layer is 0.8-2.2 μm.

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