Mist nickel electroplating appearance process for stainless steel base material

Abstract

The invention discloses a stainless steel base material mist nickel electroplating appearance technology, and belongs to the technical field of nickel electroplating. In order to solve the problems of unstable binding force, high cost and the like of electroplating fog nickel, the invention provides an appearance process for electroplating fog nickel on a stainless steel base material. The process comprises the following steps: hanging, ultrasonic degreasing, water washing I, anode electrolytic degreasing / pre-activation, water washing II, acid activation, pure water washing I, nickel electroplating impact, recycling I, pure water washing II, activation, nickel mist electroplating, recycling II, water washing III, dilute hydrochloric acid washing I, water washing IV, ultrasonic cleaning, pure water washing III, hot pure water washing, drying and hanging. According to the method, the nickel mist electroplating process is optimized, pretreatment degreasing is further optimized, nickel impact electroplating is adopted, the activation procedure is added, the nickel mist electroplating formula is adjusted and the like, the problem that the binding force of nickel mist electroplating is not stable is solved, uniform nickel mist appearance electroplating of various kinds of stainless steel is achieved, the glossiness of a plating layer is 70 degrees or below, and the cost is remarkably reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of nickel electroplating, and particularly relates to a process for electroplating a matte nickel appearance on a stainless steel substrate. Background Art

[0002] Currently, the common matte nickel appearance on the market is achieved through the sand nickel electroplating process. However, the method of pre-plating electroless nickel + sand nickel has a high cost. Since the electroless nickel coating has self-passivation properties, the bonding strength with the sand nickel coating is unstable, and the effective cycle of the sand nickel bath solution is short, requiring re-tank preparation within 24 hours, resulting in high maintenance and usage costs, and unable to meet the market's cost requirements. Therefore, it is necessary to develop a stable matte nickel formulation process to solve the problems of poor coating bonding strength and high cost of matte nickel electroplating.

[0003] CN118773683A discloses an electroplating matte nickel process, including: S1. Pre-plating nickel layer: placing the workpiece in the first electroplating solution as the cathode to pre-plate the nickel layer, and the components of the first electroplating solution are nickel sulfamate, sulfamic acid, and water; S2. Plating a phosphorus-containing bottom nickel layer: placing the workpiece with the pre-plated nickel layer in the second electroplating solution as the cathode to electroplate the phosphorus-containing bottom nickel layer, and the components of the second electroplating solution are: nickel sulfamate, nickel chloride, boric acid, sulfamic acid, phosphorus-containing additive, wetting agent, and water; S3. Plating a matte nickel layer: placing the workpiece with the electroplated phosphorus-containing bottom nickel layer in the third electroplating solution as the cathode to electroplate the matte nickel layer, and the components of the third electroplating solution are: nickel sulfamate, nickel chloride, boric acid, sulfamic acid, wetting agent, and water. This method uses an aqueous solution of nickel sulfamate to pre-plate the nickel layer, replacing the pre-plated nickel layer of hydrochloric acid and nickel chloride, electroplates a phosphorus-containing bottom nickel layer between the pre-plated nickel layer and the matte nickel layer, and does not add matte nickel additives such as polyethylene glycol and quaternary ammonium salt compounds to the electroplating solution when electroplating the matte nickel layer, making the coating crystal grains more delicate without affecting the normal electroplating efficiency. However, this method does not adjust the pre-treatment before electroplating, and its use of a phosphorus-containing electroplating solution has a scrapping cycle, is prone to environmental pollution, and adding the process of electroplating a phosphorus-containing bottom nickel layer also makes the existing equipment inapplicable. In addition, the bonding strength of the pre-plated nickel layer with the aqueous solution of nickel sulfamate is not well guaranteed, and the failure of the coating bonding strength occurs from time to time. When encountering products with a relatively thick stainless steel passivation layer, failures will occur, and the applicability and stability of the process are not good.

[0004] CN 108166032 A discloses a high-speed fog nickel electroplating process, including: S1. Substrate unwinding: Wind the substrate on the unwinding mechanism, and start the unwinding mechanism to unwind the substrate; S2. Ultrasonic chemical degreasing: Traverse the unwound substrate into the tank filled with cleaning solution, and simultaneously introduce ultrasonic waves into the tank. Under the action of ultrasonic waves, use the cleaning solution to clean the oil stains on the surface of the substrate; S3. Water washing: Traverse the substrate after degreasing into the water washing tank, and use clean water to rinse off the oil stains and cleaning solution on the surface of the substrate; S4. Electrolytic degreasing: Traverse the substrate after water washing into the degreasing electroplating tank, and use the electrolytic degreasing method to remove the oil stains on the surface of the substrate; S5. Water washing electrolytic degreasing: Traverse the substrate into the water washing electroplating tank, and use the electrolytic degreasing method to further remove the oil stains on the surface of the substrate; S6. Pickling: After step S5, traverse the substrate into the tank filled with weak acid, and use weak acid to pickle the substrate; S7. Water washing: After pickling, traverse the substrate into the water washing tank, and use clean water to wash the weak acid on the surface of the substrate; S8. Undercoat nickel: Traverse the substrate into the first nickel electroplating tank filled with electroplating solution, connect the substrate to the negative electrode of the power supply, connect the nickel anode of the first nickel electroplating tank to the positive electrode of the power supply. After starting the power supply, nickel ions adhere to the substrate, thereby forming undercoat nickel; S9. Nickel recovery: Traverse the substrate in step S8 into the air box, use the air blown out from the air box to blow off the electroplating solution on the surface of the substrate. After blowing off, collect it in the recovery tank, and use a pump to pump the electroplating solution in the recovery tank into the first nickel electroplating tank again, thereby realizing nickel recovery; S10. Water washing: Traverse the substrate into the water washing tank, and use clean water to wash the electroplating solution on the surface of the substrate; S11. Fog nickel plating: Traverse the substrate into the second nickel electroplating tank, and plate fog nickel on the basis of the undercoat nickel; S12. Traverse the substrate successively through the third, fourth, fifth, and sixth nickel electroplating tanks, thereby forming a fog nickel layer on the substrate, and the product is obtained; S13. Ultrasonic water washing: Traverse the substrate plated with fog nickel into the water tank filled with clean water, and simultaneously introduce ultrasonic waves into the water tank to wash off the electroplating solution on the fog nickel layer; S14. Drying: Traverse the product after ultrasonic water washing into the oven, and use hot air to dry the surface of the product; S15. Winding: Fix the head end of the product on the winding mechanism, and use the winding mechanism to wind the product to achieve continuous electroplating. However, this method only gives an overview of the fog nickel electroplating process and does not involve specific operations, lacking application value. Summary of the Invention

[0005] To solve the technical problems of unstable adhesion of electroplated fog nickel and high cost of the fog nickel process in the prior art, the present invention has developed a process for electroplating impact nickel + fog nickel appearance on a stainless steel substrate.

[0006] The present invention provides a process for electroplating a matte nickel appearance on a stainless steel substrate, and its process flow is as follows: hanging - ultrasonic degreasing - water washing I - anodic electrolytic degreasing / pre-activation - water washing II - acid activation - pure water washing I - electroplating shock nickel - recovery I - pure water washing II - activation - electroplating matte nickel - recovery II - water washing III - light hydrochloric acid washing I - water washing IV - ultrasonic cleaning - pure water washing III - hot pure water washing - drying - unhanging; among them, in the ultrasonic degreasing process: a slightly neutral degreasing agent is used, the degreasing temperature is 50 - 60°C, and the ultrasonic power matching is 0.4 - 0.6 kw / L; for parts without bent slits or blind holes, the ultrasonic frequency is matched to 28 - 40 kHz, and conversely, the ultrasonic frequency is matched to 50 - 70 kHz;

[0007] Anodic electrolytic degreasing / pre-activation process: the electrolysis temperature is 50 - 60°C, the electrolysis voltage is 6 - 8V, and the electrolysis current density is 3 - 5A / dm 2 , the part is in the anode in the bath solution, and the supporting electrolytic plate is in the cathode;

[0008] Acid activation process: concentrated hydrochloric acid 300 - 500 ml / L (the solvent is water) is used for acid activation;

[0009] Electroplating shock nickel process: the electroplating solution formula for electroplating shock nickel (the solvent is water) is: concentrated hydrochloric acid 90 - 110 ml / L, nickel chloride (electroplating grade) 200 - 250 g / L;

[0010] Activation process: the activation solution formula (the solvent is water) is: concentrated sulfuric acid 2 - 5 ml / L;

[0011] Electroplating matte nickel process: the electroplating solution formula for electroplating matte nickel (the solvent is water) is: nickel sulfate (electroplating grade) 180 - 250 g / L, nickel chloride (electroplating grade) 35 - 45 g / L, boric acid (electroplating grade) 30 - 45 g / L; the additive formula in the electroplating solution is: Saccharin: 0.5 - 3 g / L, Sodium Benzenesulfonate: 0.1 - 0.5 g / L, Allylsulfonic acid sodium salt (ALS): 0.5 - 1.5 g / L, 1,4 - Butynediol (BD): 0.01 - 0.05 mL / L, Sodium dodecyl sulfate (SDS): 0.01 - 1 g / L, Polyethylene glycol 600 (PEG600): 0.1 - 0.3 g / L;

[0012] Ultrasonic cleaning process: the ultrasonic power matching is 0.4 - 0.6 kw / L; for parts without bent slits or blind holes, the ultrasonic frequency is matched to 28 - 40 kHz, and conversely, the ultrasonic frequency is matched to 50 - 70 kHz.

[0013] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the ultrasonic degreasing process, a mildly alkaline degreasing agent is formulated into an aqueous solution with a mass concentration of 10-15% and a pH of 7-8.

[0014] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the ultrasonic degreasing process, the treatment time is 2-5 minutes.

[0015] Preferably, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the ultrasonic degreasing process, for parts without bent slits or blind holes, the ultrasonic power is matched to 0.4-0.5 kw / L, the ultrasonic frequency is matched to 28-40 kHz, and the treatment time is controlled to 2-4 minutes; conversely, the ultrasonic power is matched to 0.5-0.6 kw / L, the ultrasonic frequency is matched to 50-70 kHz, and the treatment time is controlled to 4-5 minutes.

[0016] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the anodic electrolytic degreasing / pre-activation process, the formula of the degreasing agent aqueous solution (with water as the solvent) is: sodium hydroxide 40-60 g / L, sodium carbonate 20-40 g / L, trisodium phosphate 15-25 g / L, and fatty alcohol polyoxyethylene ether 0.5-1.5 g / L.

[0017] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the anodic electrolytic degreasing / pre-activation process, the treatment time is 8-12 minutes.

[0018] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the acid activation process, depending on the type of stainless steel substrate, it is selected whether to add 3-5% of the corrosion inhibitor hexamethylenetetramine; when the stainless steel substrate is a composite material substrate, 3-5% of hexamethylenetetramine is also added during acid activation (i.e., the addition amount of hexamethylenetetramine is about 3-5% of the mass of the solution with 300-500 ml / L of concentrated hydrochloric acid).

[0019] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the acid activation process, acid activation is carried out at room temperature for 1-3 minutes.

[0020] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the electroplating shock nickel process, electroplating is carried out at room temperature, the electroplating solution flow rate is 300-500 L / min, the electroplating time is 30-80 seconds, and the current density is 7-10 A / dm 2 。

[0021] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the activation process, at room temperature, the electroplated shock nickel product is immersed in the activation solution for 5-10 seconds, and then directly enters the electroplating matte nickel bath.

[0022] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, during the electroplating matte nickel process, the flow rate of the electroplating solution is 300 - 500 L / min, the electroplating pH value is 3.5 - 4.2, the temperature of electroplating matte nickel is 55 - 65 °C, and the current density is 2.5 - 4 A / dm 2 , and the time is 6 - 15 min.

[0023] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, during the ultrasonic cleaning process, running water with a conductivity ≤ 10 us / cm is used.

[0024] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, during the ultrasonic cleaning process, the treatment time is 2 - 5 min.

[0025] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the pure water washing I process: running water with a conductivity ≤ 5 us / cm is used.

[0026] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the pure water washing II process: running water with a conductivity ≤ 5 us / cm is used.

[0027] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the pure water washing III process: running water with a conductivity ≤ 5 us / cm is used.

[0028] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the dilute hydrochloric acid washing I process: 2 - 5 ml / L of concentrated hydrochloric acid is used.

[0029] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the hot pure water washing process: hot water with a conductivity ≤ 5 us / cm and a temperature of 70 - 85 °C is used (the bath solution is changed every 10 hours to ensure the conductivity of pure water).

[0030] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the drying process: the drying temperature is 75 - 95 °C, and the drying time is 8 - 15 min.

[0031] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the recycling I process: the concentrated plating solution remaining on the parts is recycled, filtered, and recycled into the impact nickel bath.

[0032] Among them, in the above-mentioned process for electroplating matte nickel on a stainless steel substrate, in the recycling II process: the concentrated plating solution remaining on the parts is recycled, filtered, and recycled into the electroplating matte nickel bath.

[0033] In the present invention, the first water wash, the second water wash, the third water wash, and the fourth water wash are conventional processes, all of which adopt a two-stage countercurrent water wash (i.e., each water wash has two steps, divided into a No. 1 and a No. 2 water tank. The liquid level difference between the No. 1 and No. 2 tanks is controlled at 3 - 5 cm to enable water to overflow from the No. 2 tank to the No. 1 tank by natural gravity. The parts are first immersed in the No. 1 water wash tank and then in the No. 2 water wash tank. Clean water enters through the No. 2 water wash tank and overflows into the No. 1 tank through the pipeline connecting the No. 1 and No. 2 tanks, and finally is discharged from the No. 1 tank). The cleaning is carried out by immersing the parts in the water tank, and the immersion time is 2 - 5 seconds. Moreover, the water in the water wash tank is stirred by mechanical stirring through a same-tank pump or by injecting air through an "H-shaped perforated pipeline" at the bottom of the tank by a blower to improve the fluidity of the water and enhance the cleaning effect.

[0034] In the present invention, in each step before the drying process, the parts should enter the next step with water on their surfaces. Otherwise, it will affect the coating adhesion and the external light effect. Therefore, no additional drying step is required before the drying process.

[0035] In the present invention, the conductivity ≤ 10 μS / cm and the conductivity ≤ 5 μS / cm refer to the conductivity of water at room temperature.

[0036] In the present invention, 300 - 500 ml / L of concentrated hydrochloric acid, 90 - 110 ml / L of concentrated hydrochloric acid, 2 - 5 ml / L of concentrated hydrochloric acid, 2 - 5 ml / L of concentrated sulfuric acid, etc. mean that 1 L of the solution contains the corresponding volume of concentrated hydrochloric acid or concentrated sulfuric acid. Taking 300 - 500 ml / L of concentrated hydrochloric acid as an example, its preparation method is as follows: Add 300 - 500 ml of concentrated hydrochloric acid to a container with an effective volume of 1 L, and then add water to 1 L to obtain 300 - 500 ml / L of concentrated hydrochloric acid; this is a general method for preparing the tank solution in the chemical industry.

[0037] Advantages of the present invention:

[0038] The present invention optimizes the overall electroplating process of matte nickel, further optimizes the pretreatment degreasing, adopts impact nickel electroplating, adds an activation process, and adjusts the electroplating matte nickel formula, solving the problem of unstable coating adhesion of electroplating matte nickel. It can achieve uniform matte nickel appearance electroplating for products of various stainless steel grades such as 201, 430, 304, and 316L. The glossiness of the coating can be controlled below 70° (60° incident angle gloss meter); its process is simple, the tank solution is easy to maintain, the maintenance period is 7 days, and the cost is reduced by about 40% compared with the traditional satin nickel process. Description of the Drawings

[0039] Figure 1 It is a physical diagram of the matte nickel appearance obtained in Example 1.

[0040] Figure 2 It is a physical diagram of the matte nickel appearance obtained in Example 2. Detailed implementation mode

[0041] Specifically, a process for electroplating a matte nickel appearance on a stainless steel substrate includes the following steps:

[0042] The process flow is as follows: hanging - ultrasonic degreasing - water washing I - anodic electrolytic degreasing / pre - activation - water washing II - acid activation - pure water washing I - electroplating shock nickel - recovery I - pure water washing II - activation - electroplating matte nickel - recovery II - water washing III - light hydrochloric acid washing I - water washing IV - ultrasonic cleaning - pure water washing III - hot pure water washing - drying - unhanging;

[0043] Among them, in the ultrasonic degreasing process: a partially neutral degreasing agent is used, the degreasing temperature is 50 - 60°C, and the ultrasonic power matching is 0.4 - 0.6 kw / L; for parts without bent slits or blind holes, the ultrasonic frequency is matched to 28 - 40 kHz, otherwise the ultrasonic frequency is matched to 50 - 70 kHz;

[0044] Anodic electrolytic degreasing / pre - activation process: the electrolysis temperature is 50 - 60°C, the electrolysis voltage is 6 - 8V, and the electrolysis current density is 3 - 5 A / dm 2 , the parts are in the anode in the bath solution, and the supporting electrolytic plate is in the cathode;

[0045] Acid activation process: 300 - 500 ml / L of concentrated hydrochloric acid is used for acid activation;

[0046] Electroplating shock nickel process: the electroplating solution formula for electroplating shock nickel is: 90 - 110 ml / L of concentrated hydrochloric acid, 200 - 250 g / L of nickel chloride (electroplating grade);

[0047] Activation process: the activation solution formula is: 2 - 5 ml / L of concentrated sulfuric acid;

[0048] Electroplating matte nickel process: the electroplating solution formula for electroplating matte nickel is: 180 - 250 g / L of nickel sulfate (electroplating grade), 35 - 45 g / L of nickel chloride (electroplating grade), 30 - 45 g / L of boric acid (electroplating grade); the additive formula is: Saccharin: 0.5 - 3 g / L, Sodium Benzenesulfonate: 0.1 - 0.5 g / L, Allylsulfonic acid sodium (ALS): 0.5 - 1.5 g / L, 1,4 - Butynediol (BD): 0.01 - 0.05 mL / L, Sodium dodecyl sulfate (SDS): 0.01 - 1 g / L, Polyethylene glycol 600 (PEG600): 0.1 - 0.3 g / L;

[0049] Ultrasonic cleaning process: The ultrasonic power matching is 0.4 - 0.6 kw / L; for parts without bent slits or blind holes, the ultrasonic frequency is matched to 28 - 40 kHz, otherwise the ultrasonic frequency is matched to 50 - 70 kHz.

[0050] The existing process flow is: hanging - ultrasonic degreasing - water washing - acid activation - water washing - pre - plating nickel - phosphorus layer - recovery - water washing - activation - electroplating satin nickel - water washing - electroplating semi - bright nickel - recovery - water washing - ultrasonic cleaning - pure water washing - hot pure water washing - drying - unhanging. The present invention optimizes the overall process and further optimizes specific processes such as pretreatment degreasing, impact nickel electroplating, and electroplating fog nickel formula.

[0051] The present invention optimizes the pretreatment degreasing part and adopts two - step degreasing of ultrasonic pre - degreasing and anodic electrolytic degreasing (anodic electrolytic degreasing has the function of pre - activation).

[0052] In the ultrasonic degreasing process of the present invention, a commercially available mildly - neutral degreasing agent (mainly composed of organic surfactants) is used to prepare an aqueous solution with a concentration of 10 - 15%, the pH value is controlled at 7 - 8, and the degreasing temperature is controlled at 50 - 60°C. The ultrasonic power matching is 0.4 - 0.6 kw / L. Through multiple experiments, the power matching and frequency selection of ultrasonic waves are crucial for the cleaning effect of parts. For parts with simple structures, without bent slits or blind holes, the ultrasonic frequency is matched to 28 - 40 kHz, otherwise the frequency of 50 - 70 kHz is used. The treatment time is 2 - 5 min. The main function of this step is to remove most of the oil stains on the surface of stainless steel products. By selecting the ultrasonic frequency, the oil stains in narrow structures can be removed, reducing the degreasing pressure of the anodic electrolytic degreasing process.

[0053] Furthermore, for parts without bent slits or blind holes, the ultrasonic power matching is 0.4 - 0.5 kw / L, the ultrasonic frequency matching is 28 - 40 kHz, and the treatment time is controlled at 2 - 4 minutes; otherwise, the ultrasonic power matching is 0.5 - 0.6 kw / L, the ultrasonic frequency matching is 50 - 70 kHz, and the treatment time is controlled at 4 - 5 minutes, which can clean more efficiently and more thoroughly.

[0054] In the anodic electrolytic degreasing / pre - activation process of the present invention, the formula of the degreasing agent aqueous solution is: sodium hydroxide 40 - 60 g / L, sodium carbonate 20 - 40 g / L, trisodium phosphate 15 - 25 g / L, fatty alcohol polyoxyethylene ether 0.5 - 1.5 g / L. The temperature is controlled at 50 - 60°C, the electrolytic voltage is set at 6 - 8 V, and the current density is controlled at 3 - 5 A / dm 2, the part is in the anode in the tank solution, and the supporting electrolytic plate is in the cathode. The treatment time is 8 - 12 minutes, and the electrolysis time is long. The main function of this step is to remove the remaining oil on the stainless steel, and through the ablation effect of high-current anodic electrolysis, pre-strip and loosen the passivation layer on the stainless steel to ensure that the passivation layer on the stainless steel can be effectively removed, increase the efficiency for the subsequent pickling and activation functions, and effectively avoid the cleaning effect of single chemical pickling on the uneven-thickness stainless steel passivation layer, thus ensuring the coating adhesion of the product; using cathode electrolysis cannot achieve the effect of ablating the thick passivation film.

[0055] In the acid activation process of the present invention, industrial concentrated hydrochloric acid is used to prepare an aqueous solution with a volume fraction of 30 - 50%. According to the part situation, 3 - 5% (mass fraction) of hexamethylenetetramine as a corrosion inhibitor is added, and acid activation is carried out at room temperature with an activation time of 1 - 3 minutes. The main function of this step is to etch the passivation layer on the surface of the stainless steel to ensure the adhesion of the subsequent electroplating layer; during the production of the present invention, it is found that in a chemical reaction, the stainless steel substrate of the composite material is prone to galvanic corrosion problems, resulting in over-corrosion of the relatively active stainless steel and affecting the surface uniformity. Therefore, in the present invention, hexamethylenetetramine is added when the stainless steel substrate is a composite material substrate to slow down the corrosiveness of hydrochloric acid. Those skilled in the art can know whether the stainless steel substrate is a composite material. For example, in the embodiment of the present invention, there are 430 material rivets on 304 stainless steel, which is a stainless steel substrate of the composite material; in Example 2, it is only 316L stainless steel, which is a single-material stainless steel substrate.

[0056] In the electroplating shock nickel process of the present invention, the electroplating solution formula: 90 - 110 ml / L of concentrated hydrochloric acid, 200 - 250 g / L of nickel chloride (electroplating grade), electroplating is carried out at room temperature. The anode uses a titanium basket filled with high-purity nickel angles for electroplating grade, and is wrapped with a polypropylene anode bag to reduce the overflow of fine particles caused by the dissolution of the anode nickel angles and affect the coating quality. This tank is equipped with an electroplating filter, in which a filter core with a filtration diameter of 1 μm is installed, and the flow rate of the filter is 300 - 500 L / min. Through the H-shaped outlet pipeline at the bottom of the tank and the return pipeline on the side of the tank, a strong plating solution circulation is formed in the tank. After the part enters the plating tank, the electroplating time is 30 - 80 seconds, and the current density is 7 - 10 A / dm 2 , and in the first 2 seconds, the current continuously rises from 0 to the working current. The main function of this process is to quickly form a dense and high-adhesion nickel layer on the surface of the substrate, providing a good base for the subsequent electroplating of matte nickel. Among them, the large-flow filter is to avoid a large amount of hydrochloric acid overflow caused by using air stirring, resulting in too rapid change of hydrochloric acid concentration and affecting electroplating stability. The 2-second current rising time is to avoid burning the part with a large current.

[0057] The present invention uses impact nickel electroplating to apply a bottom coating to stainless steel products. In the electroplating formulation, the concentration of hydrochloric acid is increased, and the current is increased slowly. This can not only improve the conductivity of the plating solution, enhance the uniformity of the bottom coating and the film-forming speed, but also reactivate the surface of the stainless steel during the slow current increase process, improving the adhesion of the product. Compared with the phosphorus-containing pre-nickel plating layer, the impact nickel plating layer used in the present invention is not easily self-passivated, has good adhesion to the subsequent mist nickel layer, and there is no replacement cycle for the waste of the phosphorus-containing pre-nickel plating solution, resulting in less environmental pollution and good sustainable productivity.

[0058] In the activation process of the present invention, the activation solution formulation is: prepare a 2 - 5 ml / L solution with concentrated sulfuric acid (98% analytical pure) and pure water. At room temperature, the product pre-plated with impact nickel is immersed in it for 5 - 10 seconds, and then directly enters the electroplating mist nickel tank. The main function of this step is to maintain the activity of the pre-nickel plating layer and improve the adhesion of the plating layer in the low-current area.

[0059] During production, the porosity of the stainless steel pre-nickel plating is relatively large, and the overall coverage is not good. Multiple water washes are likely to cause sporadic adhesion failure of the stainless steel substrate, with a proportion between 2 - 5%. After testing, by adding an activation process between the electroplating impact nickel process and the electroplating mist nickel process in the present invention and using a sulfuric acid solution for activation between the plating layers, the failure proportion can be reduced to about 0.1%, which has an obvious effect on improving the qualified rate of the product.

[0060] In the electroplating mist nickel process of the present invention, the plating solution formulation is: nickel sulfate (electroplating grade) 180 - 250 g / L, nickel chloride (electroplating grade) 35 - 45 g / L, boric acid (electroplating grade) 30 - 45 g / L. The additive formulation is: Saccharin: 0.5 - 3 g / L, Sodium Benzenesulfonate: 0.1 - 0.5 g / L, Allylsulfonic acid sodium salt (ALS): 0.5 - 1.5 g / L, 1,4 - Butynediol (BD): 0.01 - 0.05 mL / L, Sodium dodecyl sulfate (SDS): 0.01 - 1 g / L, Polyethylene glycol 600 (PEG600): 0.1 - 0.3 g / L. The pH value is controlled at 3.5 - 4.2, the temperature is controlled at 55 - 65 °C, and the current density is controlled at 2.5 - 4 A / dm 2, the electroplating time is controlled within 6 - 15 minutes. The anode uses a titanium basket filled with electroplating-grade high-purity nickel anodes, which are wrapped with polypropylene anode bags to reduce the spillage of fine particles caused by the dissolution of the nickel anodes and affect the coating quality. The tank is equipped with an electroplating filter, in which a filter core with a filtration diameter of 1μm is installed. The flow rate of the filter is 300 - 500 L / min. Through the H-shaped outlet pipeline at the bottom of the tank and the return pipeline on the side of the tank, a strong plating solution circulation is formed in the tank to avoid using air stirring, reduce heat loss, impurity entry, and stabilize the plating solution. The main function of this step is to form a matte nickel appearance coating on the stainless steel surface.

[0061] The existing satin nickel formula will add inorganic particulate matte agent components: silicon dioxide (SiO2): particle size 0.5 - 5μm, concentration 2 - 8 g / L, aluminum oxide (Al2O3): particle size 1 - 3μm, concentration 1 - 5 g / L, polytetrafluoroethylene (PTFE) particles: 0.5 - 3 g / L (with lubricity). The electroplating matte nickel formula adopted in the present invention is completely different from the prior art. Through several groups of ingredient combinations and concentration adjustments, it can achieve the plating of a matte nickel appearance at extremely low cost, and obtain the finished product in one step without multiple electroplating. Moreover, the formula of the present invention only needs to replace the activated carbon filter element for online filtration for 4 hours during the maintenance period, and then add according to the additive formula. There is no problem of scrapping and replacement, with little environmental pollution and good sustainable productivity.

[0062] In the pure water washing and hot pure water washing processes of the present invention, pure water with a certain conductivity is used for cleaning to avoid water mark residues on the coating surface.

[0063] In the ultrasonic cleaning process of the present invention, flowing water with a conductivity ≤ 10 us / cm is used; the treatment time is 2 - 5 minutes.

[0064] The pure water washing I process of the present invention: uses flowing water with a conductivity ≤ 5 us / cm.

[0065] The pure water washing II process of the present invention: uses flowing water with a conductivity ≤ 5 us / cm.

[0066] The pure water washing III process of the present invention: uses flowing water with a conductivity ≤ 5 us / cm.

[0067] In the dilute hydrochloric acid washing I process of the present invention, 2 - 5 ml / L of concentrated hydrochloric acid is used, which can effectively remove the residual matte nickel additive components on the surface of the workpiece and avoid the appearance defect of "yellowing" at the cracks, blind holes, and acute angle structures.

[0068] The hot pure water washing process of the present invention: uses hot water with a conductivity ≤ 5 us / cm and a temperature of 70 - 85°C (the tank solution is replaced every 10 hours to ensure the conductivity of the pure water).

[0069] In the drying process of the present invention, a double - circulation air wheel is adopted. The return air enters from the bottom of the tank body and the air exits beside the tank body. The temperature is controlled at 75 - 95 °C, and the drying time is controlled at 8 - 15 min.

[0070] In the recovery process I of the present invention, the concentrated plating solution remaining on the parts is recovered. It can be filtered and recycled into the impact nickel plating tank, reducing emissions and used to supplement the plating solution, which is a way of clean production in electroplating.

[0071] In the recovery process II of the present invention, the concentrated plating solution remaining on the parts is recovered. It can be filtered and recycled into the electroplated mist nickel plating tank, reducing emissions and used to supplement the plating solution, which is a way of clean production in electroplating.

[0072] The present invention will be further described in detail below through examples, but the protection scope of the present invention is not limited to the scope of the described examples.

[0073] Example 1

[0074] Taking a flat part made of 304 stainless steel with a thickness of 2.5 mm as the base material and having 430 - material rivets, the electroplated mist nickel process is as follows.

[0075] 1. Hanging process: Connect to the hanging tooling through the process holes.

[0076] 2. Ultrasonic degreasing process: Use a slightly neutral degreasing agent, with a configured concentration of 14%, a pH value controlled at 8, and a degreasing temperature controlled at 60 °C. The ultrasonic power matching is 0.5 kw / L, the ultrasonic frequency is 28 kHz, and the treatment time is 3 min.

[0077] 3. Anodic electrolytic degreasing / pre - activation process: Use a self - prepared formula, with 50 g / L of sodium hydroxide, 35 g / L of sodium carbonate, 25 g / L of trisodium phosphate, and 0.5 g / L of fatty alcohol polyoxyethylene ether. The temperature is controlled at 50 °C, the electrolytic voltage is set at 6.5 V, and the current density is controlled at 3.5 A / dm 2 , the parts are in the anode in the tank solution, and the supporting electrolytic plate is in the cathode. The treatment time is 10 min.

[0078] 4. Acid activation process: Use industrial concentrated hydrochloric acid to prepare an aqueous solution with a volume fraction of 35%, add 3% of the corrosion inhibitor hexamethylenetetramine, and carry out acid activation at room temperature. The activation time is 2.5 min.

[0079] 5. Electroplating shock nickel process: Using a self - prepared formula, 95 ml / L of hydrochloric acid (37% analytical pure), 220 g / L of nickel chloride (electroplating grade), electroplating is carried out at room temperature of 26°C. The anode uses a titanium basket filled with high - purity nickel angles for electroplating grade and is wrapped with a polypropylene anode bag to reduce the spillage of fine particles caused by the dissolution of anode nickel angles and affect the coating quality. This tank is equipped with an electroplating filter, in which 10 filter cores with a filtration diameter of 1μm are installed. The flow rate of the filter is 500 L / min, the electroplating time is 50 seconds, and the current density is 8.5 A / dm 2 , where in the first 2 seconds, the current continuously rises from 0 to the working current.

[0080] 6. Recycling process: Recover the residual concentrated plating solution on the parts to reduce emissions, and this solution can be reused in the plating tank.

[0081] 7. Activation process: Using a self - prepared formula, a 2 ml / L solution is prepared with concentrated sulfuric acid (98% analytical pure) and pure water. At room temperature, the products pre - plated with shock nickel are soaked in it for 5 seconds, and then directly enter the electroplating mist nickel tank.

[0082] 8. Electroplating mist nickel process: The plating solution uses a self - prepared formula, 220 g / L of nickel sulfate (electroplating grade), 42 g / L of nickel chloride (electroplating grade), 35 g / L of boric acid (electroplating grade). Additive formula: Saccharin: 2.0 g / L, Sodium Benzenesulfonate: 0.4 g / L, Allylsulfonic acid sodium salt (ALS): 0.5 g / L, 1,4 - Butynediol (BD): 0.01 mL / L, Sodium dodecyl sulfate (SDS): 0.5 g / L, Polyethylene glycol 600 (PEG600): 0.1 g / L. The pH value is controlled at 3.5, the temperature is controlled at 58°C, and the current density is controlled at 3.5 A / dm 2 , and the electroplating time is controlled at 10 min. The anode uses a titanium basket filled with high - purity nickel angles for electroplating grade and is wrapped with a polypropylene anode bag to reduce the spillage of fine particles caused by the dissolution of anode nickel angles and affect the coating quality. This tank is equipped with an electroplating filter, in which a filter core with a filtration diameter of 1μm is installed. The flow rate of the filter is 400 L / min.

[0083] 9. Recycling and light hydrochloric acid washing process: Recover the residual concentrated plating solution on the parts to reduce emissions, and this solution can be reused in the plating tank. In the water - washing tank of this step, 2.5 ml / L of hydrochloric acid (37% analytical pure) is added.

[0084] 10. Ultrasonic cleaning process: Using flowing pure water, the pure water has a conductivity of 8 us / cm at room temperature, and the ultrasonic power matching is 0.6 kw / L. For parts with simple structures, without bending slits or blind holes, the ultrasonic frequency is matched to 28 kHz, and the treatment time is 2 min.

[0085] 11. Pure water washing, hot pure water washing process: The conductivity of the pure water used is 3 us / cm, and the purity of the pure water tank is maintained by means of flowing water. The temperature of the hot pure water tank is controlled at 80 °C, and the tank liquid is replaced every 10 hours to ensure the conductivity of the pure water.

[0086] 12. Drying process: A double-circulation air wheel is adopted. The return air enters from the bottom of the tank body and the air exits beside the tank body. The temperature is controlled at 85 °C, and the drying time is controlled at 12 min.

[0087] A uniform mist nickel appearance is obtained, and its physical picture is as Figure 1 shown; the measured glossiness is 56 - 68° (60° incident angle gloss meter), and the qualified rate reaches about 98% (the qualified rate of sand nickel is generally 92%), and the cost is 0.7 - 0.8 yuan / dm 2 (the cost of sand nickel is generally 1.1 - 1.2 yuan / dm 2 ).

[0088] In this embodiment, 3 methods are selected to test the coating adhesion:

[0089] 1. Bend Test

[0090] Principle: Stress is generated between the coating and the substrate through plastic deformation, and whether the coating peels off is observed.

[0091] Steps: The specimen is repeatedly bent 180° around a cylinder with a specified diameter (such as 1 - 4 times the thickness of the base material). Check whether the coating at the bending part peels or flakes off.

[0092] Judgment criterion: No visible peeling to the naked eye is qualified (refer to ASTM B571).

[0093] 2. File Test

[0094] Principle: The filing force is used to damage the edge of the coating to detect the bonding strength.

[0095] Steps: Use a coarse-tooth file to file the edge of the plated part at a 45° angle unidirectionally. Observe whether the coating warps or falls off.

[0096] 3. Electrolysis method

[0097] Electrolyte: 5 mol / L NaOH, temperature 80 °C. Current density: 100 mA / cm 2 , time 30 minutes. The test piece is at the electrolytic cathode.

[0098] After testing by the above 3 methods, no adhesion problem appears in the mist nickel appearance obtained in this embodiment, and the adhesion is stable.

[0099] Example 2

[0100] Using 316L stainless steel with a thickness of 0.45 mm as the base material, a flat part with a folding slit, the process method of electroplating matte nickel is as follows.

[0101] 1. Hanging process: Connect to the fixture tooling through the process holes.

[0102] 2. Ultrasonic degreasing process: Use a slightly neutral degreasing agent, with a configured concentration of 10%, pH value controlled at 7.5, and degreasing temperature controlled at 55°C. The ultrasonic power matching is 0.5 kw / L, the ultrasonic frequency is 60 kHz, and the treatment time is 4 min.

[0103] 3. Anodic electrolytic degreasing / pre-activation process: Use a self-prepared formula, 40 g / L of sodium hydroxide, 25 g / L of sodium carbonate, 18 g / L of trisodium phosphate, and 1.5 g / L of fatty alcohol polyoxyethylene ether. The temperature is controlled at 55°C, the electrolytic voltage is set at 7.5 V, and the current density is controlled at 4 A / dm 2 , the parts are in the anode in the bath solution, and the supporting electrolytic plate is in the cathode. The treatment time is 12 min.

[0104] 4. Acid activation process: Use industrial concentrated hydrochloric acid to prepare an aqueous solution with a volume fraction of 50%, and carry out acid activation at room temperature. The activation time is 1.5 min.

[0105] 5. Electroplating impact nickel process: Use a self-prepared formula, 105 ml / L of hydrochloric acid (37% analytical pure), 250 g / L of nickel chloride (electroplating grade), and electroplate at a room temperature of 21°C. The anode uses a titanium basket filled with electroplating-grade high-purity nickel anodes, which are wrapped with polypropylene anode bags to reduce the overflow of fine particles caused by the dissolution of anode nickel anodes and affect the coating quality. The bath is equipped with an electroplating filter, in which 10 filter cores with a filtration diameter of 1 μm are installed, the flow rate of the filter is 500 L / min, the electroplating time is 40 seconds, and the current density is 7.5 A / dm 2 , and in the first 2 seconds, the current rises continuously from 0 to the working current.

[0106] 6. Recycling process: Recycle the residual plating solution concentrate on the parts to reduce emissions, and this solution can be reused in the plating bath.

[0107] 7. Activation process: Use a self-prepared formula, prepare a 5 ml / L solution with concentrated sulfuric acid (98% analytical pure) and pure water, and soak the pre-plated impact nickel products in it at room temperature for 8 seconds, and then directly enter the electroplating matte nickel bath.

[0108] 8. Electroplating of matte nickel process: The plating solution uses a self - prepared formula, including nickel sulfate (electroplating grade) 200 g / L, nickel chloride (electroplating grade) 44 g / L, boric acid (electroplating grade) 35 g / L. Additive formula: Saccharin: 1.5 g / L, Sodium Benzenesulfonate: 0.5 g / L, Allylsulfonic acid sodium salt (ALS): 1.2 g / L, 1,4 - Butynediol (BD): 0.02 mL / L, Sodium dodecyl sulfate (SDS): 0.5 g / L, Polyethylene glycol 600 (PEG600): 0.1 g / L. The pH value is controlled at 3.8, the temperature is controlled at 58 °C, and the current density is controlled at 3 A / dm 2 , and the electroplating time is controlled at 7 min. The anode uses a titanium basket filled with high - purity nickel corners for electroplating grade and is wrapped with a polypropylene anode bag to reduce the influence of fine particles overflow caused by the dissolution of anode nickel corners on the coating quality. The tank is equipped with an electroplating filter, in which a filter element with a filtration diameter of 1 μm is installed, and the flow rate of the filter is 500 L / min.

[0109] 9. Recovery and light hydrochloric acid washing process: Recover the residual concentrated plating solution on the parts to reduce emissions, and this solution can be reused in the plating tank. In the water - washing tank of this step, add hydrochloric acid (37% analytical pure) at 5 ml / L.

[0110] 10. Ultrasonic cleaning process: Use flowing pure water. The pure water has a conductivity of 8 us / cm at room temperature, and the ultrasonic power matching is 0.6 kw / L. The ultrasonic frequency is matched at 60 kHz, and the treatment time is 4 min.

[0111] 11. Pure water washing and hot pure water washing process: The pure water has a conductivity of 3 us / cm, and the purity of the pure water tank is maintained by the way of flowing water. The temperature of the hot pure water tank is controlled at 85 °C, and the tank solution is changed every 10 hours to ensure the conductivity of the pure water.

[0112] 12. Drying process: Adopt a double - circulation air wheel, the return air enters from the bottom of the tank, and the air exits beside the tank. The temperature is controlled at 75 °C, and the drying time is controlled at 10 min.

[0113] Get a uniform matte nickel appearance, and its physical drawing is as Figure 2 shown; The measured glossiness is 60 - 70° (60° incident angle glossmeter), the qualified rate of the finished product is about 98.5%, and the cost is 0.7 - 0.8 yuan / dm 2 .

[0114] In this embodiment, 3 methods are selected to test the adhesion of the coating:

[0115] 1. Bend Test

[0116] Principle: Stress is generated between the coating and the substrate through plastic deformation to observe whether the coating peels off.

[0117] Steps: Repeatedly bend the specimen 180° around a cylinder with a specified diameter (such as 1 - 4 times the thickness of the base material). Check whether the coating at the bending area peels or flakes off.

[0118] Judgment criterion: It is qualified if no visible peeling is observed by the naked eye (refer to ASTM B571).

[0119] 2. File Test

[0120] Principle: The filing force is used to damage the edge of the coating to detect the bonding strength.

[0121] Steps: Use a coarse - toothed file to unidirectionally file the edge of the plated part at a 45° angle. Observe whether the coating warps or falls off.

[0122] 3. Electrolysis Method

[0123] Electrolyte: 5mol / L NaOH, temperature 80°C. Current density: 100mA / cm 2 , time 30 minutes. The test piece is at the electrolytic cathode.

[0124] After being tested by the above three methods, no adhesion problems were found in the appearance of the matte nickel obtained in this example, and the adhesion is stable.

Claims

1. The appearance process of electroplating matte nickel on a stainless steel substrate is characterized in that: The process flow is as follows: hanging - ultrasonic degreasing - water washing I - anodic electrolytic degreasing / pre - activation - water washing II - acid activation - pure water washing I - electroplating shock nickel - recovery I - pure water washing II - activation - electroplating matte nickel - recovery II - water washing III - light hydrochloric acid washing I - water washing IV - ultrasonic cleaning - pure water washing III - hot pure water washing - drying - unhanging; among them, in the ultrasonic degreasing process: a mildly - neutral degreasing agent is used, the degreasing temperature is 50 - 60 °C, and the ultrasonic power matching is 0.4 - 0.6 kw / L; for parts without bent slits or blind holes, the ultrasonic frequency is matched to 28 - 40 kHz, otherwise the ultrasonic frequency is matched to 50 - 70 kHz; Anodic electrolytic degreasing / pre-activation process: The electrolytic temperature is 50 - 60 °C, the electrolytic voltage is 6 - 8 V, and the electrolytic current density is 3 - 5 A / dm 2 , the parts are anodes in the bath solution, and the supporting electrolytic plates are cathodes; In the acid activation process: concentrated hydrochloric acid at 300 - 500 ml / L is used for acid activation; In the electroplating shock nickel process: the electroplating solution formula for electroplating shock nickel is: concentrated hydrochloric acid 90 - 110 ml / L, nickel chloride 200 - 250 g / L; In the activation process: the activation solution formula is: concentrated sulfuric acid 2 - 5 ml / L; In the electroplating matte nickel process: the electroplating solution formula for electroplating matte nickel is: nickel sulfate 180 - 250 g / L, nickel chloride 35 - 45 g / L, boric acid 30 - 45 g / L; the additive formula is: saccharin: 0.5 - 3 g / L, sodium benzenesulfinate: 0.1 - 0.5 g / L, allylsulfonic acid sodium: 0.5 - 1.5 g / L, 1,4 - butynediol: 0.01 - 0.05 mL / L, sodium dodecyl sulfate: 0.01 - 1 g / L, polyethylene glycol 600: 0.1 - 0.3 g / L; In the ultrasonic cleaning process: the ultrasonic power matching is 0.4 - 0.6 kw / L; for parts without bent slits or blind holes, the ultrasonic frequency is matched to 28 - 40 kHz, otherwise the ultrasonic frequency is matched to 50 - 70 kHz.

2. The electroplating process for the appearance of matte nickel on a stainless steel substrate according to claim 1, characterized in that: In the ultrasonic degreasing process, at least one of the following is satisfied: The mildly - neutral degreasing agent is formulated into an aqueous solution with a mass concentration of 10 - 15% and a pH of 7 - 8; The treatment time is 2 - 5 min; For parts without bent slits or blind holes, the ultrasonic power matching is 0.4 - 0.5 kw / L, the ultrasonic frequency matching is 28 - 40 kHz, and the treatment time is controlled at 2 - 4 minutes. Otherwise, the ultrasonic power matching is 0.5 - 0.6 kw / L, the ultrasonic frequency matching is 50 - 70 kHz, and the treatment time is controlled at 4 - 5 minutes.

3. The electroplating process for the appearance of matte nickel on a stainless steel substrate according to claim 1, characterized in that: In the anodic electrolytic degreasing / pre - activation process, at least one of the following is satisfied: The formula of the degreasing agent aqueous solution is: sodium hydroxide 40 - 60 g / L, sodium carbonate 20 - 40 g / L, trisodium phosphate 15 - 25 g / L, fatty alcohol polyoxyethylene ether 0.5 - 1.5 g / L; The treatment time is 8 - 12 min.

4. The electroplating process for the appearance of matte nickel on a stainless steel substrate according to claim 1, characterized in that: In the acid activation process, at least one of the following is satisfied: When the stainless - steel substrate is a composite - material substrate, 3 - 5% of hexamethylenetetramine is also added during acid activation; Acid activation is carried out at room temperature for 1 - 3 min.

5. The electroplating process for the appearance of satin nickel on a stainless steel substrate according to claim 1, characterized in that: In the electroplating shock nickel process, electroplating is carried out at room temperature, the electroplating solution flow rate is 300 - 500 L / min, the electroplating time is 30 - 80 seconds, and the current density is 7 - 10 A / dm 2 .

6. The electroplating process for the appearance of matte nickel on a stainless steel substrate according to claim 1, wherein: In the activation process, at room temperature, the electroplated shock - nickel product is immersed in the activation solution for 5 - 10 seconds, and then directly enters the electroplating matte - nickel bath.

7. The electroplating process for the appearance of matte nickel on a stainless steel substrate according to claim 1, wherein: In the electroplating of matte nickel process, the flow rate of the electroplating solution is 300 - 500 L / min, the electroplating pH value is 3.5 - 4.2, the temperature of electroplating matte nickel is 55 - 65 °C, and the current density is 2.5 - 4 A / dm 2 , and the time is 6 - 15 min.

8. The electroplating process for the appearance of matte nickel on a stainless steel substrate according to claim 1, characterized in that: In the ultrasonic cleaning process, at least one of the following is satisfied: Use flowing water with a conductivity ≤ 10 us / cm; The processing time is 2 - 5 min.

9. The electroplating process for the matte nickel appearance on a stainless steel substrate according to claim 1, wherein: At least one of the following conditions should be met: Pure water washing I process: Use running water with a conductivity ≤ 5 us / cm. Pure water washing II process: Use running water with a conductivity ≤ 5 us / cm. Pure water washing III process: Use running water with a conductivity ≤ 5 us / cm. Dilute hydrochloric acid washing I process: Use 2 - 5 ml / L of concentrated hydrochloric acid. Hot pure water washing process: Use hot water with a conductivity ≤ 5 us / cm and a temperature of 70 - 85 °C. Drying process: The drying temperature is 75 - 95 °C, and the drying time is 8 - 15 min.

10. The electroplating process for the appearance of matte nickel on a stainless steel substrate according to claim 1, wherein: At least one of the following conditions should be met: Recovery I process: Recover the residual concentrated plating solution on the parts and filter it back into the impact nickel bath. Recovery II process: Recover the residual concentrated plating solution on the parts and filter it back into the electroplated fog nickel bath.

Images