High-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process and plating layer structure

Abstract

The invention discloses a low-hydrogen embrittlement potassium chloride cadmium plating process for high-strength steel and a plating layer structure. The low-hydrogen embrittlement potassium chloride cadmium plating process comprises the steps that cobalt-titanium alloy plating, potassium chloride cadmium plating and hexavalent chromium passivation are sequentially carried out on a high-strength steel substrate. The cobalt-titanium alloy plating process parameters comprise 160-200 g / L of cobalt sulfate heptahydrate, 8-12 g / L of potassium fluotitanate, 2-8 g / L of sodium fluoride, 80-120 g / L of sodium sulfate, 30-50 g / L of sodium hydrogen succinate and 8-12 mL / L of a displacement agent, the pH value of a plating solution is 3.8-4.4, the temperature of a plating tank is 20-35 DEG C, the cathode current density is 1-2 A / dm < 2 >, and the cathode movement is 4-6 m / min. The hydrogen brittleness test is carried out according to HB 5067.1-2005 Part 1 of Hydrogen brittleness Test of Plating Process: Mechanical Method, and the test result meets the standard requirement. The process is stable in plating solution, excellent in plating performance and good in market prospect.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, specifically relating to a high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process and coating structure. Background Technology

[0002] High-strength components in the aerospace industry are highly susceptible to hydrogen embrittlement and stress corrosion cracking. Currently, the industry uses electroplating cadmium-titanium alloys to prepare protective layers for these high-strength steel components. [1] Current cadmium-titanium alloy electroplating processes typically involve directly electroplating the cadmium-titanium alloy onto a high-strength structural steel substrate, followed by hexavalent chromium passivation. Internationally, cyanide plating is used to prepare cadmium-titanium alloy coatings, while domestically, ammoniacal triacetic acid-ammonium chloride plating is generally employed. Experimental studies show that most of the hydrogen in cadmium-titanium alloy electroplated samples of A100 steel parts exists within the coating, with only a very small amount penetrating into the substrate. [2] It is generally believed that titanium in cadmium-titanium alloy coatings can combine with hydrogen to form titanium trihydride, which can effectively prevent hydrogen atoms from diffusing towards the high-strength structural steel substrate.

[0003] However, both cyanide-plated cadmium titanium alloys and cyanide-free cadmium-plated titanium alloys suffer from poor plating solution stability. [3] The maintenance of the plating bath is difficult. The standard electrode potential of titanium is -1.63V, making electrochemical deposition of titanium ions in the plating bath challenging. Therefore, additives with strong cathodic polarization cannot be used in the plating bath. Currently, the cadmium-titanium alloy coatings prepared in my country have relatively rough surfaces, are not dense enough, and have relatively low corrosion resistance.

[0004] The invention patent application CN 119980226 A, entitled "A Cyanide-Free Cadmium-Iron Alloy Plating Process for High-Strength Steel," discloses a new technique involving sequential plating of nickel-titanium alloy, cadmium-iron alloy, and hexavalent chromium passivation onto a high-strength steel substrate, attempting to replace the current cadmium-titanium alloy plating process. However, the nickel-titanium alloy plating bath used contains citrate with high coordination capacity, resulting in low current efficiency and high hydrogen evolution, which is unfavorable for preparing a low-hydrogen-embrittlement coating structure.

[0005] References: [1]. Naval Factory 4805, Beijing Aeronautical Institute, Institute 621, etc., Cyanide-free electroplating process of cadmium-titanium alloy [J], Aviation Technology, 1980, 23(18): 29-34. [2]. Yu Bo, Tang Zhihui, Peng Chao, et al. Effect of cyanide-free electroplating of cadmium-titanium alloy on hydrogen embrittlement of steel substrate [J], Electroplating & Finishing, 2011, 33(11): 1-4. [3]. Lin Qian, Study on cyanide-free electroplating process of cadmium-titanium alloy and electrodeposition behavior [D], Nanchang, Nanchang University of Aeronautics and Astronautics, 2018. Summary of the Invention

[0006] To overcome the problems of poor stability of cadmium-titanium alloy plating solutions and low corrosion resistance of coatings on high-strength steel workpieces for aerospace applications, this invention provides a low-hydrogen-embrittlement potassium chloride cadmium plating process for high-strength steel. To achieve the above objectives, this invention adopts the following technical solution: A high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process includes the following steps: (1) Pretreatment of high-strength steel workpieces, including degreasing and sulfuric acid anodic electrolytic activation; (2) After pretreatment of high-strength steel workpieces, a cobalt-titanium alloy coating is prepared by a cobalt-titanium alloy plating process. (3) After high-strength steel workpieces are plated with cobalt-titanium alloy, a cyanide-free cadmium plating layer is prepared by potassium chloride cadmium plating process. (4) High-strength steel workpieces are subjected to hydrogen removal treatment after potassium chloride cadmium plating; (5) After hydrogen removal, high-strength steel workpieces are prepared with hexavalent chromium passivation film using a hexavalent chromium passivation process; The cobalt-titanium alloy plating process includes the following components and process parameters: Cobalt sulfate heptahydrate 160–200 g / L, potassium fluorotitanate 8–12 g / L, sodium fluoride 2–8 g / L, sodium sulfate 80–120 g / L, sodium hydrogen succinate 30–50 g / L, leveling agent 8–12 mL / L, plating bath pH 3.8–4.4, plating bath temperature 20–35℃, cathode current density 1–2 A / dm³ 2 The cathode moves at a speed of 4–6 m / min. The positional agent comprises 20-30 g / L of the condensation reaction product of salicylic acid and epichlorohydrin, 80-120 g / L of sodium saccharin, 200-300 mL / L of sodium propylene sulfonate with a mass fraction of 35%, 4-8 mL / L of ethoxylated acidic phosphate, and 140-160 mL / L of ethanol.

[0007] In some embodiments, the positioning agent is prepared as follows: Add half the required amount of pure water to the reaction vessel. Add ethanol according to the process formula, then add the condensation reaction product of salicylic acid and epichlorohydrin. Stir until homogeneous. Add sodium saccharin, sodium propylene sulfonate (35% by mass), and ethoxylated acidic phosphate according to the process formula. Stir until the sodium saccharin is completely dissolved, then add pure water to the required volume.

[0008] In some embodiments, cobalt particles are used as the anode. The cobalt particles are placed in a titanium anode basket and covered with an anode bag. The area ratio of the anode to the cathode is (3-6):1.

[0009] In some embodiments, the process composition and parameters for the sulfuric acid anodic electrolytic activation are as follows: Sulfuric acid concentration of 160–240 g / L, operating at room temperature, with the workpiece to be plated as the anode, and an anode current density of 0.6–1.2 A / dm³. 2 Electrolysis for 30–50 seconds.

[0010] In some embodiments, the potassium chloride cadmium plating process employs the PULIZIER NCC-617 potassium chloride cyanide-free cadmium plating process: Cadmium chloride 25–35 g / L, potassium chloride 100–140 g / L, PULIZIER NCC-617 AC complexing agent 100–140 g / L, PULIZIER NCC-617 Base auxiliary agent 25–30 mL / L, PULIZIER NCC-617 Bri brightener 1.5–2.5 mL / L, PULIZIER NCC-617 HCD high-zone brightener 5–10 mL / L, plating bath temperature 20–35℃, plating solution pH 7–9, cathode current density 0.5–1.5 A / dm³ 2 The cathode moves at a speed of 2–4 m / min.

[0011] In some embodiments, the hexavalent chromium passivation process employs the HC-5 high-protection, low-chromium color passivation process: The volume concentration of HC-5 high-protection low-chromium colored passivating agent is 2% to 4%, the passivation temperature is 20 to 35℃, the pH value of the passivation solution is 1.3 to 2.0, the passivation time is 5 to 20 seconds, and it is carried out with weak air agitation or workpiece oscillation.

[0012] In some embodiments, the hexavalent chromium passivation process employs the OVG-31 military-green passivation process: OVG-31 military green passivating agent 80~120mL / L, passivation solution pH value 1.0~1.6, passivation temperature 20~30℃, air agitation or oscillation of the plated parts, passivation time 30~90s.

[0013] A high-strength steel low-hydrogen embrittlement cyanide-free cadmium plating layer structure includes a high-strength steel substrate, and a cobalt-titanium alloy coating, a cyanide-free cadmium plating layer, and a hexavalent chromium passivation film sequentially prepared on the high-strength steel substrate.

[0014] In some embodiments, the thickness of the cobalt-titanium alloy coating is 4–10 μm.

[0015] In some embodiments, the cobalt-titanium alloy coating contains 0.5% to 3% titanium by mass.

[0016] In some embodiments, the thickness of the cyanide-free cadmium plating layer is 5–22 μm.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process disclosed in this invention does not contain a high-coordination-capacity ligand in the cobalt-titanium alloy plating bath, has high current efficiency in the plating bath, and very little hydrogen evolution during the cobalt-titanium alloy plating process, which is beneficial for preparing a low-hydrogen embrittlement coating. 2. The potassium chloride cadmium plating process for high-strength steel with low hydrogen embrittlement disclosed in this invention involves plating a cobalt-titanium alloy onto a high-strength steel substrate. The titanium atoms in the cobalt-titanium alloy coating can react with hydrogen atoms to generate titanium trihydride compounds, thereby effectively preventing the diffusion of hydrogen atoms toward the substrate and avoiding hydrogen embrittlement of the high-strength steel substrate. 3. The high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process disclosed in this invention involves plating a cobalt-titanium alloy onto a high-strength steel substrate followed by potassium chloride cadmium plating. The cobalt-titanium alloy coating can effectively prevent the diffusion of hydrogen atoms toward the substrate. 4. The high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process disclosed in this invention provides electrochemical protection for the cobalt-titanium alloy plating layer, overcoming the defect that the cadmium-titanium alloy plating layer directly prepared on the surface of high-strength steel does not have electrochemical protection. 5. The high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process disclosed in this invention produces a cadmium plating layer structure that withstands neutral salt spray tests for more than 30 times the 96-hour white rust-free time required by aerospace standards. Attached Figure Description

[0018] The accompanying drawings, which are provided to further illustrate the invention and form part of this application, do not constitute an undue limitation of the invention.

[0019] In the attached diagram, Figure 1 This is a schematic diagram of the coating structure prepared in Embodiments 1, 2, 3 and 4 of the present invention. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0021] A low-hydrogen-embrittlement potassium chloride cadmium plating process for high-strength steel includes high-strength steel pretreatment, preparation of a cobalt-titanium alloy coating, a potassium chloride cadmium plating coating, hydrogen removal, and preparation of a passivation film on the high-strength steel substrate from the inside out.

[0022] The surface of a high-strength steel workpiece substrate is degreased and activated by sulfuric acid anodic electrolysis.

[0023] Preferably, the process composition and parameters for the sulfuric acid anodic electrolytic activation are as follows: Sulfuric acid concentration of 160–240 g / L, operating at room temperature, with the workpiece to be plated as the anode, and an anode current density of 0.6–1.2 A / dm³. 2 Electrolysis for 30–50 seconds.

[0024] After pretreatment, a cobalt-titanium alloy coating is prepared using the cobalt-titanium alloy plating process of the present invention. Preferably, the thickness of the cobalt-titanium alloy coating is 4–10 μm, and the mass fraction of titanium in the coating is 0.5%–3%.

[0025] Cobalt sulfate heptahydrate 160–200 g / L, potassium fluorotitanate 8–12 g / L, sodium fluoride 2–8 g / L, sodium sulfate 80–120 g / L, sodium hydrogen succinate 30–50 g / L, leveling agent 8–12 mL / L, plating bath pH 3.8–4.4, plating bath temperature 20–35℃, cathode current density 1–2 A / dm³ 2 The cathode moves at a speed of 4–6 m / min.

[0026] Preferably, the positioning agent comprises 20-30 g / L of the condensation reaction product of salicylic acid and epichlorohydrin, 80-120 g / L of sodium saccharin, 200-300 mL / L of sodium propylene sulfonate with a mass fraction of 35%, 4-8 mL / L of ethoxylated acidic phosphate, and 140-160 mL / L of ethanol.

[0027] Add half the required amount of pure water to the reaction vessel. Add ethanol and the condensation reaction product of salicylic acid and epichlorohydrin according to the process formula. Stir until homogeneous. Add sodium saccharin, sodium propylene sulfonate (35% by mass), and ethoxylated acid phosphate according to the process formula. Stir until sodium saccharin is completely dissolved. Then add pure water to the required volume.

[0028] Preferably, cobalt particles are used as the anode, and the cobalt particles are placed in a titanium anode basket and covered with an anode bag. The area ratio of the anode to the cathode is (3-6):1.

[0029] Preferably, during production, solid potassium fluorotitanate is added to the plating solution to maintain its mass concentration within the range required by the process.

[0030] After high-strength steel workpieces are plated with cobalt-titanium alloy, a cyanide-free cadmium plating layer is prepared using the existing potassium chloride cadmium plating process.

[0031] Preferably, the thickness of the cyanide-free cadmium plating layer is 5–22 μm.

[0032] Preferably, the cyanide-free cadmium plating layer is prepared using the PULIZIER NCC-617 potassium chloride cyanide-free cadmium plating process developed by Chaobang Chemical. Cadmium chloride 25–35 g / L, potassium chloride 100–140 g / L, PULIZIER NCC-617 AC complexing agent 100–140 g / L, PULIZIER NCC-617 Base auxiliary agent 25–30 mL / L, PULIZIER NCC-617 Bri brightener 1.5–2.5 mL / L, PULIZIER NCC-617 HCD high-zone brightener 5–10 mL / L, plating bath temperature 20–35℃, plating solution pH 7–9, cathode current density 0.5–1.5 A / dm³ 2 The cathode moves at a speed of 2–4 m / min.

[0033] High-strength steel workpieces are subjected to hydrogen removal treatment after potassium chloride cadmium plating: the plated parts are dehydrogenated at 190-200℃ for 20-30 hours.

[0034] After hydrogen removal, high-strength steel workpieces are prepared with a passivation film using the current hexavalent passivation process.

[0035] Preferably, the passivation film is prepared using HC-5 high-protection, low-chromium colored passivation agent from Chaobang Chemical Co., Ltd. The volume concentration of HC-5 high-protection low-chromium colored passivating agent is 2% to 4%, the passivation temperature is 20 to 35℃, the pH value of the passivation solution is 1.3 to 2.0, the passivation time is 5 to 20 seconds, and it is carried out with weak air agitation or workpiece oscillation.

[0036] Preferably, the passivation film is prepared using OVG-31 military-green passivating agent from Chaobang Chemical Co., Ltd. OVG-31 military green passivating agent 80~120mL / L, passivation solution pH value 1.0~1.6, passivation temperature 20~30℃, air agitation or oscillation of the plated parts, passivation time 30~90s.

[0037] Preferably, the specific process of the passivation process is as follows: "2% nitric acid brightening → water washing → passivation → water washing → blowing away residual water on the surface of the plated part with high-pressure air".

[0038] After passivation, high-strength steel workpieces are dried at 55-60℃ for 10-15 minutes.

[0039] Example 1: like Figure 1 As shown, a high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process and coating structure include pretreatment of high-strength steel substrate 1, preparation of cobalt-titanium alloy coating 2, cyanide-free cadmium plating coating 3, hydrogen removal, and preparation of hexavalent chromium colored passivation film 4 on the high-strength steel substrate 1 from the inside to the outside.

[0040] 1. Pre-processing: The high-strength steel workpiece substrate 1 is subjected to the following process: "alkaline chemical degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → sulfuric acid anodic electrolytic activation → water washing".

[0041] The sulfuric acid anodic electrolytic activation adopts the following anodic electrolytic activation process: Sulfuric acid 200g / L, room temperature operation, with the workpiece to be plated as the anode, anolyte current density 1A / dm³ 2 Electrolysis for 40 seconds.

[0042] 2. Cobalt-plated titanium alloy: After pretreatment of high-strength steel workpieces, a cobalt-titanium alloy coating 2 is prepared using the cobalt-titanium alloy plating process of the present invention. The coating thickness is 8μm and the mass fraction of titanium in the coating is 2%.

[0043] 1) Preparation of the positioning agent: The leveling agents include 25 g / L of the condensation reaction product of salicylic acid and epichlorohydrin, 100 g / L of sodium saccharin, 250 mL / L of sodium propylene sulfonate (35% by mass), 6 mL / L of ethoxylated acidic phosphate, and 150 mL / L of ethanol.

[0044] Add half the required amount of pure water to the reaction vessel. Add ethanol and the condensation reaction product of salicylic acid and epichlorohydrin according to the process formula. Stir until homogeneous. Add sodium saccharin, sodium propylene sulfonate (35% by mass), and ethoxylated acid phosphate according to the process formula. Stir until sodium saccharin dissolves. Then add pure water to the required volume.

[0045] 2) Cobalt-plated titanium alloy: Cobalt sulfate heptahydrate 180 g / L, potassium fluorotitanate 10 g / L, sodium fluoride 5 g / L, sodium sulfate 100 g / L, sodium hydrogen succinate 40 g / L, leveling agent 10 mL / L, plating bath pH 4.1, plating tank temperature 25℃, cathode current density 1.5 A / dm³ 2 The cathode moves at a speed of 5 m / min. Cobalt granules are used as the anode, and the cobalt granules are placed in a titanium anode basket. An anode bag is placed over the anode basket, and the area ratio of the anode to the cathode is 4:1. During production, solid potassium fluorotitanate is added to the plating solution to maintain its mass concentration within the process range.

[0046] 3. Potassium chloride cadmium plating: After high-strength steel workpieces are plated with cobalt-titanium alloy, a cyanide-free cadmium plating layer 3 is prepared using the PULIZIER NCC-617 potassium chloride cyanide-free cadmium plating process developed by Chaobang Chemical, with a plating thickness of 12μm.

[0047] Cadmium chloride 30 g / L, potassium chloride 120 g / L, PULIZIER NCC-617 AC complexing agent 120 g / L, PULIZIER NCC-617 Base auxiliary agent 28 mL / L, PULIZIER NCC-617 Bri brightener 2 mL / L, PULIZIER NCC-617 HCD high-zone brightener 8 mL / L, plating bath temperature 28℃, plating solution pH 8, cathode current density 1 A / dm³ 2 The cathode moves at a speed of 3 m / min.

[0048] 4. Hydrogen removal: High-strength steel workpieces are plated with potassium chloride cadmium and then dehydrogenated at 200℃ for 24 hours.

[0049] 5. Passivation: After hydrogen removal, hexavalent chromium colored passivation film was prepared using HC-5 high-protection low-chromium colored passivation agent from Chaobang Chemical.

[0050] The volume concentration of HC-5 high-protection low-chromium colored passivating agent is 3%, the passivation temperature is 28℃, the pH of the passivation solution is 1.7, the passivation time is 12s, and the workpiece is oscillating.

[0051] The specific process is as follows: "Brightening with 2% nitric acid (by volume) → Water washing → Passivation → Water washing → Blowing away residual water on the surface of the plated part with high-pressure air".

[0052] 6. Drying: After passivation, the high-strength steel workpiece is dried at 60℃ for 10 minutes.

[0053] Example 2: like Figure 1 As shown, a high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process and coating structure include pretreatment of high-strength steel substrate 1, preparation of cobalt-titanium alloy coating 2, cyanide-free cadmium plating coating 3, hydrogen removal, and preparation of hexavalent chromium colored passivation film 4 on the high-strength steel substrate 1 from the inside to the outside.

[0054] 1. Pre-processing: The high-strength steel workpiece substrate 1 is subjected to the following process: "alkaline chemical degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → sulfuric acid anodic electrolytic activation → water washing".

[0055] The sulfuric acid anodic electrolytic activation adopts the following anodic electrolytic activation process: Sulfuric acid 240 g / L, room temperature operation, with the workpiece to be plated as the anode, anolyte current density 0.6 A / dm³ 2 Electrolysis for 30 seconds.

[0056] 2. Cobalt-plated titanium alloy: After pretreatment of high-strength steel workpieces, a cobalt-titanium alloy coating 2 is prepared using the cobalt-titanium alloy plating process of the present invention. The coating thickness is 8μm and the mass fraction of titanium in the coating is 2%.

[0057] 1) Preparation of the positioning agent: The leveling agents include 25 g / L of the condensation reaction product of salicylic acid and epichlorohydrin, 100 g / L of sodium saccharin, 250 mL / L of sodium propylene sulfonate (35% by mass), 6 mL / L of ethoxylated acidic phosphate, and 150 mL / L of ethanol.

[0058] Add half the required amount of pure water to the reaction vessel. Add ethanol and the condensation reaction product of salicylic acid and epichlorohydrin according to the process formula. Stir until homogeneous. Add sodium saccharin, sodium propylene sulfonate (35% by mass), and ethoxylated acid phosphate according to the process formula. Stir until sodium saccharin dissolves. Then add pure water to the required volume.

[0059] 2) Cobalt-plated titanium alloy: Cobalt sulfate heptahydrate 200 g / L, potassium fluorotitanate 12 g / L, sodium fluoride 8 g / L, sodium sulfate 120 g / L, sodium hydrogen succinate 50 g / L, leveling agent 10 mL / L, plating bath pH 4.4, plating bath temperature 20℃, cathode current density 1.5 A / dm³ 2 The cathode moves at a speed of 5 m / min. Cobalt granules are used as the anode, and the cobalt granules are placed in a titanium anode basket. An anode bag is placed over the anode basket, and the area ratio of the anode to the cathode is 4:1. During production, solid potassium fluorotitanate is added to the plating solution to maintain its mass concentration within the process range.

[0060] 3. Potassium chloride cadmium plating: After high-strength steel workpieces are plated with cobalt-titanium alloy, a cyanide-free cadmium plating layer 3 is prepared using the PULIZIER NCC-617 potassium chloride cyanide-free cadmium plating process developed by Chaobang Chemical, with a plating thickness of 12μm.

[0061] Cadmium chloride 35g / L, potassium chloride 100g / L, PULIZIER NCC-617 AC complexing agent 140g / L, PULIZIER NCC-617 Base auxiliary agent 28mL / L, PULIZIER NCC-617 Bri brightener 2mL / L, PULIZIER NCC-617 HCD high-zone brightener 8mL / L, plating bath temperature 20℃, plating solution pH 7, cathode current density 1A / dm³ 2 The cathode moves at a speed of 3 m / min.

[0062] 4. Hydrogen removal: High-strength steel workpieces are plated with potassium chloride cadmium and then dehydrogenated at 200℃ for 24 hours.

[0063] 5. Passivation: After hydrogen removal, hexavalent chromium colored passivation film was prepared using HC-5 high-protection low-chromium colored passivation agent from Chaobang Chemical.

[0064] The volume concentration of HC-5 high-protection low-chromium colored passivating agent is 4%, the passivation temperature is 20℃, the pH of the passivation solution is 2, the passivation time is 10s, and the workpiece is oscillating.

[0065] The specific process is as follows: "Brightening with 2% nitric acid (by volume) → Water washing → Passivation → Water washing → Blowing away residual water on the surface of the plated part with high-pressure air".

[0066] 6. Drying: After passivation, the high-strength steel workpiece is dried at 60℃ for 10 minutes.

[0067] Example 3: like Figure 1 As shown, a high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process and coating structure include pretreatment of high-strength steel substrate 1, preparation of cobalt-titanium alloy coating 2, potassium chloride cadmium plating coating 3, hydrogen removal, and preparation of hexavalent chromium military green passivation film 4 on the high-strength steel substrate 1 from the inside to the outside.

[0068] 1. Pre-processing: The high-strength steel workpiece substrate 1 is subjected to the following process: "alkaline chemical degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → sulfuric acid anodic electrolytic activation → water washing".

[0069] The sulfuric acid anodic electrolytic activation adopts the following anodic electrolytic activation process: Sulfuric acid 160 g / L, room temperature operation, with the workpiece to be plated as the anode, anolyte current density 1.2 A / dm³ 2 Electrolysis for 50 seconds.

[0070] 2. Cobalt-plated titanium alloy: After pretreatment of high-strength steel workpieces, a cobalt-titanium alloy coating 2 is prepared using the cobalt-titanium alloy plating process of the present invention. The coating thickness is 8μm and the mass fraction of titanium in the coating is 2%.

[0071] 1) Preparation of the positioning agent: The leveling agents include 25 g / L of the condensation reaction product of salicylic acid and epichlorohydrin, 100 g / L of sodium saccharin, 250 mL / L of sodium propylene sulfonate (35% by mass), 6 mL / L of ethoxylated acidic phosphate, and 150 mL / L of ethanol.

[0072] Add half the required amount of pure water to the reaction vessel. Add ethanol and the condensation reaction product of salicylic acid and epichlorohydrin according to the process formula. Stir until homogeneous. Add sodium saccharin, sodium propylene sulfonate (35% by mass), and ethoxylated acid phosphate according to the process formula. Stir until sodium saccharin dissolves. Then add pure water to the required volume.

[0073] 2) Cobalt-plated titanium alloy: The plating solution contained 160 g / L cobalt sulfate heptahydrate, 8 g / L potassium fluorotitanate, 2 g / L sodium fluoride, 80 g / L sodium sulfate, 30 g / L sodium hydrogen succinate, and 10 mL / L leveling agent. The pH of the plating solution was 3.8, the plating tank temperature was 35℃, and the cathode current density was 1.2 A / dm³. 2 The cathode moves at a speed of 5 m / min. Cobalt granules are used as the anode, and the cobalt granules are placed in a titanium anode basket. An anode bag is then placed over the anode basket, and the area ratio of the anode to the cathode is 4:1. During production, solid potassium fluorotitanate is added to the plating solution to maintain its mass concentration within the process range.

[0074] 3. Potassium chloride cadmium plating: After high-strength steel workpieces are plated with cobalt-titanium alloy, a cyanide-free cadmium plating layer 3 is prepared using the PULIZIER NCC-617 potassium chloride cyanide-free cadmium plating process developed by Chaobang Chemical, with a plating thickness of 12μm.

[0075] Cadmium chloride 25 g / L, potassium chloride 140 g / L, PULIZIER NCC-617 AC complexing agent 100 g / L, PULIZIER NCC-617 Base auxiliary agent 28 mL / L, PULIZIER NCC-617 Bri brightener 2 mL / L, PULIZIER NCC-617 HCD high-zone brightener 8 mL / L, plating bath temperature 35℃, plating solution pH 9, cathode current density 1 A / dm³ 2 The cathode moves at a speed of 3 m / min.

[0076] 4. Hydrogen removal: High-strength steel workpieces are plated with potassium chloride cadmium and then dehydrogenated at 200℃ for 24 hours.

[0077] 5. Passivation: After hydrogen removal, a hexavalent chromium military green passivation film was prepared using OVG-31 military green passivating agent from Chaobang Chemical.

[0078] OVG-31 military green passivating agent 100mL / L, passivation solution pH 1.3, passivation temperature 25℃, oscillating plated parts, passivation time 60s.

[0079] The specific process is as follows: "Brightening with 2% nitric acid (by volume) → Water washing → Passivation → Water washing → Blowing away residual water on the surface of the plated part with high-pressure air".

[0080] 6. Drying: After passivation, the high-strength steel workpiece is dried at 60℃ for 10 minutes.

[0081] Example 4: like Figure 1 As shown, a high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process and coating structure include pretreatment of high-strength steel substrate 1, preparation of cobalt-titanium alloy coating 2, cyanide-free cadmium plating coating 3, hydrogen removal, and preparation of hexavalent chromium military green passivation film 4 on the high-strength steel substrate 1 from the inside to the outside.

[0082] 1. Pre-processing: The high-strength steel workpiece substrate 1 is subjected to the following process: "alkaline chemical degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → sulfuric acid anodic electrolytic activation → water washing".

[0083] The sulfuric acid anodic electrolytic activation adopts the following anodic electrolytic activation process: Sulfuric acid 220 g / L, room temperature operation, with the workpiece to be plated as the anode, anolyte current density 0.8 A / dm³ 2 Electrolysis for 45 seconds.

[0084] 2. Cobalt-plated titanium alloy: After pretreatment of high-strength steel workpieces, a cobalt-titanium alloy coating 2 is prepared using the cobalt-titanium alloy plating process of the present invention. The coating thickness is 8μm and the mass fraction of titanium in the coating is 2%.

[0085] 1) Preparation of the positioning agent: The leveling agents include 25 g / L of the condensation reaction product of salicylic acid and epichlorohydrin, 100 g / L of sodium saccharin, 250 mL / L of sodium propylene sulfonate (35% by mass), 6 mL / L of ethoxylated acidic phosphate, and 150 mL / L of ethanol.

[0086] Add half the required amount of pure water to the reaction vessel. Add ethanol and the condensation reaction product of salicylic acid and epichlorohydrin according to the process formula. Stir until homogeneous. Add sodium saccharin, sodium propylene sulfonate (35% by mass), and ethoxylated acid phosphate according to the process formula. Stir until sodium saccharin dissolves. Then add pure water to the required volume.

[0087] 2) Cobalt-plated titanium alloy: Cobalt sulfate heptahydrate 190 g / L, potassium fluorotitanate 11 g / L, sodium fluoride 7 g / L, sodium sulfate 110 g / L, sodium hydrogen succinate 45 g / L, leveling agent 10 mL / L, plating bath pH 4.2, plating bath temperature 25℃, cathode current density 1.2 A / dm³ 2The cathode moves at a speed of 5 m / min. Cobalt granules are used as the anode, and the cobalt granules are placed in a titanium anode basket. An anode bag is then placed over the anode basket, and the area ratio of the anode to the cathode is 4:1. During production, solid potassium fluorotitanate is added to the plating solution to maintain its mass concentration within the process range.

[0088] 3. Potassium chloride cadmium plating: After high-strength steel workpieces are plated with cobalt-titanium alloy, a cyanide-free cadmium plating layer 3 is prepared using the PULIZIER NCC-617 potassium chloride cyanide-free cadmium plating process developed by Chaobang Chemical, with a plating thickness of 12μm.

[0089] Cadmium chloride 28 g / L, potassium chloride 110 g / L, PULIZIER NCC-617 AC complexing agent 130 g / L, PULIZIER NCC-617 Base auxiliary agent 28 mL / L, PULIZIER NCC-617 Bri brightener 2 mL / L, PULIZIER NCC-617 HCD high-zone brightener 8 mL / L, plating bath temperature 25℃, plating solution pH 8.5, cathode current density 1 A / dm³ 2 The cathode moves at a speed of 3 m / min.

[0090] 4. Hydrogen removal: High-strength steel workpieces are plated with potassium chloride cadmium and then dehydrogenated at 200℃ for 24 hours.

[0091] 5. Passivation: After hydrogen removal, a hexavalent chromium military green passivation film was prepared using OVG-31 military green passivating agent from Chaobang Chemical.

[0092] OVG-31 military green passivating agent 120mL / L, passivation solution pH 1.6, passivation temperature 23℃, air-oscillated plated parts, passivation time 60s.

[0093] The specific process is as follows: "Brightening with 2% nitric acid (by volume) → Water washing → Passivation → Water washing → Blowing away residual water on the surface of the plated part with high-pressure air".

[0094] 6. Drying: After passivation, the high-strength steel workpiece is dried at 60℃ for 10 minutes.

[0095] Experimental Example 1: The high-strength steel is designated as 23Co14Ni12Cr3Mo. Hydrogen embrittlement test bars were prepared according to HB 5067.1–2005 "Hydrogen embrittlement test of plating process - Part 1: Mechanical method". Cobalt-titanium alloy coating and cyanide-free cadmium plating were sequentially prepared on the surface of the degreasing test bar according to the process requirements of Example 1. Then, hydrogen was removed at 200°C for 24 hours. According to the HB 5067.1–2005 standard, the test bar did not break after being stretched for 200 hours, and the test results met the standard requirements.

[0096] Experimental Example 2: According to GB / T 10125–2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", the high-strength steel low-hydrogen embrittlement potassium chloride cadmium-plated samples prepared in Examples 1, 2, 3, and 4 showed no white rust on their surfaces after 3000 hours of neutral salt spray testing. The cyanide-free cadmium-plated layer structure prepared in this invention has a neutral salt spray test resistance time that is more than 31 times the current industry requirement of 96 hours.

[0097] Experimental Example 3: The high-strength steel potassium chloride cadmium-plated samples prepared in Examples 1, 2, 3 and 4 were tested for adhesion strength using the thermal shock test method according to GB / T 5270–2005 "Review of Test Methods for Adhesion Strength of Electrodeposition and Chemical Deposition of Metallic Coatings on Metal Substrates". The samples were heated to 300°C in a heating furnace and held for 60 minutes. They were then removed and rapidly cooled in water at room temperature. No blistering or peeling of the coating was observed, indicating good adhesion.

[0098] Experimental Example 4: The high-strength steel potassium chloride cadmium-plated samples prepared in Examples 1, 2, 3, and 4 were subjected to a mold test for 28 days in accordance with GJB 150.9A–2009 "Laboratory Environmental Testing Methods for Military Equipment Part 10: Mold Test". No mold grew on the surface of the samples, which meets the requirements of industry standards.

[0099] Experimental Example 5: The cobalt-titanium alloy plating bath was prepared as follows: cobalt sulfate heptahydrate 180 g / L, potassium fluorotitanate 10 g / L, sodium fluoride 5 g / L, sodium sulfate 100 g / L, sodium hydrogen succinate 40 g / L, and leveling agent 10 mL / L. The pH of the plating bath was 4.1, and the temperature was 25℃. The current efficiency of the plating bath was determined by coulometric method according to JB / T 7704.3-1995 "Test Methods for Electroplating Solutions - Cathode Current Efficiency Test". A coulometer (model KYA-BDAs-A1) from Suzhou Keyuan Instrument Co., Ltd. was used for measurement, and the cathode current density was 1.5 A / dm³. 2 The current efficiency is 99.48%.

[0100] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. It should be noted that, for those skilled in the art, based on the principles and concepts of the embodiments of the present invention, several modifications and improvements can be made in terms of specific implementation methods and application scope, and these should all fall within the protection scope of the present invention.

Claims

1. A potassium chloride cadmium plating process for high-strength steel with low hydrogen embrittlement, characterized in that, The process includes the following steps: (1) Pretreatment of high-strength steel workpieces, including degreasing and sulfuric acid anodic electrolytic activation; (2) After pretreatment of high-strength steel workpieces, a cobalt-titanium alloy coating is prepared by a cobalt-titanium alloy plating process. (3) After high-strength steel workpieces are plated with cobalt-titanium alloy, a cyanide-free cadmium plating layer is prepared by potassium chloride cadmium plating process. (4) High-strength steel workpieces are subjected to hydrogen removal treatment after potassium chloride cadmium plating; (5) After hydrogen removal, high-strength steel workpieces are prepared with hexavalent chromium passivation film using a hexavalent chromium passivation process; The cobalt-titanium alloy plating process includes the following components and process parameters: Cobalt sulfate heptahydrate 160–200 g / L, potassium fluorotitanate 8–12 g / L, sodium fluoride 2–8 g / L, sodium sulfate 80–120 g / L, sodium hydrogen succinate 30–50 g / L, leveling agent 8–12 mL / L, plating bath pH 3.8–4.4, plating bath temperature 20–35℃, cathode current density 1–2 A / dm³ 2 The cathode moves at a speed of 4–6 m / min. The positional agent comprises 20-30 g / L of the condensation reaction product of salicylic acid and epichlorohydrin, 80-120 g / L of sodium saccharin, 200-300 mL / L of sodium propylene sulfonate with a mass fraction of 35%, 4-8 mL / L of ethoxylated acidic phosphate, and 140-160 mL / L of ethanol.

2. The high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process according to claim 1, characterized in that, The positioning agent is prepared as follows: Add half the required amount of pure water to the reaction vessel. Add ethanol according to the process formula, then add the condensation reaction product of salicylic acid and epichlorohydrin. Stir until homogeneous. Add sodium saccharin, sodium propylene sulfonate (35% by mass), and ethoxylated acidic phosphate according to the process formula. Stir until the sodium saccharin is completely dissolved, then add pure water to the required volume.

3. The potassium chloride cadmium plating process for high-strength steel with low hydrogen embrittlement as described in claim 1, characterized in that: Cobalt particles are used as the anode. The cobalt particles are placed in a titanium anode basket and an anode bag is placed over the anode basket. The area ratio of the anode to the cathode is (3-6):

1.

4. The high-strength steel low-hydrogen embrittlement potassium chloride cadmium plating process according to claim 1, characterized in that, The process composition and parameters for the sulfuric acid anodic electrolytic activation are as follows: Sulfuric acid concentration of 160–240 g / L, operating at room temperature, with the workpiece to be plated as the anode, and an anode current density of 0.6–1.2 A / dm³. 2 Electrolysis for 30–50 seconds.

5. The potassium chloride cadmium plating process for high-strength steel with low hydrogen embrittlement as described in claim 1, characterized in that, The potassium chloride cadmium plating process described above uses the PULIZIER NCC-617 potassium chloride cyanide-free cadmium plating process. Cadmium chloride 25–35 g / L, potassium chloride 100–140 g / L, PULIZIER NCC-617 AC complexing agent 100–140 g / L, PULIZIER NCC-617 Base auxiliary agent 25–30 mL / L, PULIZIER NCC-617 Bri brightener 1.5–2.5 mL / L, PULIZIER NCC-617 HCD high-zone brightener 5–10 mL / L, plating bath temperature 20–35℃, plating solution pH 7–9, cathode current density 0.5–1.5 A / dm³ 2 The cathode moves at a speed of 2–4 m / min.

6. The potassium chloride cadmium plating process for high-strength steel with low hydrogen embrittlement as described in claim 1, characterized in that, The hexavalent chromium passivation process described above employs the HC-5 high-protection, low-chromium color passivation process: The volume concentration of HC-5 high-protection, low-chromium colored passivating agent is 2%–4%, the passivation temperature is 20–35℃, the pH value of the passivation solution is 1.3–2.0, the passivation time is 5–20 seconds, and it is applied with weak air agitation or workpiece oscillation. Alternatively, the OVG-31 military-grade passivation process can be used: OVG-31 military green passivating agent 80~120mL / L, passivation solution pH value 1.0~1.6, passivation temperature 20~30℃, air agitation or oscillation of the plated parts, passivation time 30~90s.

7. A high-strength steel low-hydrogen embrittlement cyanide-free cadmium plating layer structure, characterized in that: It includes a high-strength steel substrate, and a cobalt-titanium alloy coating, a cyanide-free cadmium plating layer, and a hexavalent chromium passivation film sequentially prepared on the high-strength steel substrate.

8. The high-strength steel low-hydrogen embrittlement cyanide-free cadmium plating layer structure as described in claim 7, characterized in that: The thickness of the cobalt-titanium alloy coating is 4–10 μm.

9. The high-strength steel low-hydrogen embrittlement cyanide-free cadmium plating layer structure as described in claim 7, characterized in that: The cobalt-titanium alloy coating contains 0.5% to 3% titanium by mass.

10. The high-strength steel low-hydrogen embrittlement cyanide-free cadmium plating layer structure as described in claim 7, characterized in that: The thickness of the cyanide-free cadmium plating layer is 5–22 μm.

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