A method for improving the stability of a bath for electroless nickel plating under barrel plating conditions and an additive

Abstract

The present application belongs to the technical field of material surface treatment, and particularly relates to a method for improving the stability of a chemical nickel plating bath under barrel plating conditions and an additive. The method comprises the following steps: preparing a debugging agent for debugging the plating bath; determining the usable service life of the chemical nickel plating bath and the plating speed on the surface of the used substrate; preparing a stabilizer according to the determined plating speed; and adding the stabilizer according to the proportion of the service life of the chemical nickel plating bath in the usable service life. Compared with the commonly used heavy metal salt stabilizer, the stabilizer used in the present application does not contain heavy metals, is friendly to the environment, can adapt to the relatively harsh barrel plating conditions, has only a very small influence on the plating speed under the condition of maintaining the stability of the chemical nickel plating bath in the entire service life, thereby greatly improving the production efficiency and ensuring the product quality.

Description

Technical Field

[0001] This invention belongs to the field of material surface treatment technology, specifically relating to a method for improving the stability of electroless nickel plating bath under barrel plating conditions and an additive. Background Technology

[0002] Electroless nickel plating is a common surface treatment method. The resulting nickel-phosphorus alloy coating exhibits excellent corrosion resistance, wear resistance, and uniform thickness, making it widely used in industry. However, because its process is based on an autocatalytic chemical reaction, "positive feedback catalysis" can easily occur during plating, leading to uncontrolled chemical reactions. Especially in barrel plating, the friction and impact between workpieces during rolling generate micron or nano-sized particles. These floating particles can act as active sites for new nickel deposition. When a long plating time is required, these particles may trigger a significant nickel reduction reaction throughout the nickel bath, resulting in a large amount of black deposits inside the barrel. This necessitates cleaning the barrel and significant maintenance or even replacement of the plating solution. This not only increases the workload of on-site personnel and reduces efficiency but also increases costs.

[0003] Traditional electroless nickel plating stabilizers are generally based on heavy metal salts, which can cause environmental pollution and significantly affect the plating rate. Therefore, developing a stabilizer that has minimal impact on the plating rate and is environmentally friendly, suitable for electroless barrel nickel plating, along with corresponding addition strategies, is crucial. Based on this, the technical solution of this invention is proposed. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a method for improving the stability of electroless nickel plating baths under barrel plating conditions, the method comprising the following steps:

[0005] (1) Prepare the conditioning agent for plating solution conditioning;

[0006] (2) Determine the available lifespan of the electroless nickel plating bath used and the plating rate on the surface of the substrate used.

[0007] (3) Prepare a stabilizer based on the plating rate measured in step (2);

[0008] (4) Based on the ratio of the service life of the electroless nickel plating bath to its usable lifespan, add stabilizer periodically.

[0009] Wherein: the adjusting agent is composed of ethoxylated propynyl alcohol and propoxylated propynyl alcohol;

[0010] The stabilizer is composed of ethoxylated propynyl alcohol and propoxylated propynyl alcohol, or the stabilizer is composed of propynyl alcohol, ethoxylated propynyl alcohol and propoxylated propynyl alcohol.

[0011] Preferably, in step (1), the conditioning agent is composed of ethoxylated propynyl alcohol and propoxylated propynyl alcohol in a molar ratio of 1:1. The main function of the conditioning agent used for plating solution conditioning is to determine the composition of the stabilizer by its effect on the plating rate of the plating solution.

[0012] Preferably, in step (2), the plating rate on the substrate surface includes V1 and V2;

[0013] V1 refers to the plating rate of the electroless nickel plating bath under production process conditions when the adjusting agent is added, and the amount of adjusting agent added is 200 mg / L.

[0014] V2 refers to the plating rate of the electroless nickel plating bath under production process conditions without the addition of conditioning agents. Freshly prepared electroless nickel plating bath solution must be used for the measurement.

[0015] Additionally, it should be noted that, under the same substrate (including other base metal layers, such as electroplated nickel), the workpiece is subjected to electroless nickel plating, and the deposition rate of the electroless nickel is measured. The testing method is an industry-standard method, such as X-ray fluorescence.

[0016] Preferably, in step (3), when V1 decreases by ≤5% compared to V2, the stabilizer and the adjusting agent are the same; when V1 decreases by >5% compared to V2, the stabilizer is prepared as follows: for every additional 1% decrease in plating rate, add 5% molar fraction of propargyl alcohol to the adjusting agent, up to a maximum of 25% molar fraction of propargyl alcohol (because under normal circumstances, at an addition amount of 200 mg / L, the adjusting agent cannot cause a plating rate decrease of more than 10%), thus obtaining the stabilizer.

[0017] Preferably, in step (4), the amount of stabilizer added is determined by the ratio of the used cycle of the electroless nickel plating bath to its usable life cycle. Specifically, the initial amount of stabilizer added to the electroless nickel plating bath is 200 mg / L, and then 50 mg / L is added every cycle; when the used cycle reaches 1 / 3 to 2 / 3 of the life cycle, 30 mg / L is added every cycle; when the used cycle reaches 2 / 3 or more of the life cycle, 15 mg / L is added every cycle.

[0018] Based on the same technical concept, another aspect of the present invention is to provide an additive that improves the stability of electroless nickel plating baths under barrel plating conditions, the additive comprising an adjusting agent and a stabilizer; wherein:

[0019] The conditioning agent is composed of ethoxylated propynyl alcohol and propoxylated propynyl alcohol;

[0020] The stabilizer is composed of ethoxylated propynyl alcohol and propoxylated propynyl alcohol, or the stabilizer is composed of propynyl alcohol, ethoxylated propynyl alcohol and propoxylated propynyl alcohol.

[0021] The beneficial effects of this invention are as follows:

[0022] The method for improving the stability of electroless nickel plating bath under barrel plating conditions described in this invention involves adding additives that do not contain heavy metals or other environmentally harmful components to the electroless nickel plating bath. This significantly improves the stability of the bath during the electroless nickel plating barrel plating process while having only a negligible impact on the plating rate, thereby greatly improving production efficiency, ensuring product quality, and achieving excellent overall results. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] In the embodiments, the method for evaluating the long-term stability of the electroless nickel plating bath is as follows:

[0025] Electroless nickel plating is performed on the workpiece using the same substrate (including other base metal layers, such as electroplated nickel). The same plating parameters are applied, including temperature, pH, and loading. The plating drum is observed for visible black spots, patches, or lumps after continuous plating for a certain period. When visible black spots, patches, or lumps appear on the drum, it indicates that nickel particles have been generated in the plating bath during the plating process, and that the concentration of these particles has reached a high level and has deposited on the drum. Therefore, the time when visible black spots, patches, or lumps first appear on the drum is the standard for judging stability; the longer this time, the later the black spots, patches, or lumps appear, indicating a more stable plating bath.

[0026] Example 1

[0027] In this embodiment of the invention, the composition of the chemical plating bath and the plating process conditions are as follows:

[0028] Nickel ions: 5.3 g / L;

[0029] Sodium hypophosphite monohydrate: 30 g / L;

[0030] Malic acid: 9.6 g / L;

[0031] Citric acid: 10.5g / L

[0032] Lactic acid: 22g / L;

[0033] Ammonia solution: 12ml / L;

[0034] Temperature: 85±2℃;

[0035] pH: 4.5 ± 0.1

[0036] The production service life of this electroless nickel plating bath has been determined to be 8 cycles.

[0037] Methods to improve the stability of electroless nickel plating baths under barrel plating conditions include the following steps:

[0038] (1) Prepare an adjusting agent, the components of which are ethoxylated propynyl alcohol and propoxylated propynyl alcohol in a molar ratio of 1:1;

[0039] (2) Take two portions of electroless nickel plating bath solution, and add an adjusting agent to one portion of the electroless nickel plating bath solution at a concentration of 200 mg / L;

[0040] (3) Two steel sheets of identical size were degreased and pickled, then weighed, and then placed in two separate electroless nickel plating baths for 1 hour each, and weighed again. The weight gain of the steel sheet in the bath with added conditioning agent was calculated to be 0.93 compared to the weight gain of the steel sheet in the bath without added agent.

[0041] (4) Compared to the requirement that the plating rate decrease should not exceed 5%, the actual decrease was an additional 2%. Therefore, the stabilizer composition was determined, namely, 10% propargyl alcohol was added to the stabilizer.

[0042] (5) Use two freshly prepared electroless nickel plating solutions, and add 200 mg / L of stabilizer to one of them. Use these two solutions to perform barrel plating on an equal number of small steel screws in a barrel plating tank, replacing the parts with a new batch every 2 hours, for a total of 8 hours of continuous plating.

[0043] (6) The results showed that the solution without stabilizer was obviously turbid and blackened, and dark-colored sediments were produced in the tank. However, the solution with stabilizer did not show the above phenomena, and there were no obvious sediments in the tank.

[0044] (7) Subsequently, 50 mg / L of stabilizer was added to the tank solution for each cycle, until the third cycle, when 30 mg / L of stabilizer was added per cycle. Then, until the sixth cycle, 15 mg / L of stabilizer was added per cycle. During this period, no turbidity or large amounts of black sediment appeared in the tank solution.

[0045] Example 2

[0046] In this embodiment of the invention, the composition of the chemical plating bath and the plating process conditions are as follows:

[0047] Nickel sulfate: 30 g / L;

[0048] Sodium hypophosphite monohydrate: 15 g / L;

[0049] Ammonium chloride: 50 g / L;

[0050] Sodium citrate: 60g / L

[0051] Potassium antimony tartrate: 4 mg / L (calculated as antimony)

[0052] Temperature: 85±2℃;

[0053] pH: 4.0-4.5

[0054] The production lifespan of this electroless nickel plating bath has been determined to be 6 cycles.

[0055] Methods to improve the stability of electroless nickel plating baths under barrel plating conditions include the following steps:

[0056] (1) Prepare an adjusting agent, the components of which are ethoxylated propynyl alcohol and propoxylated propynyl alcohol in a molar ratio of 1:1;

[0057] (2) Take two portions of electroless nickel plating bath solution, and add an adjusting agent to one portion of the electroless nickel plating bath solution at a concentration of 200 mg / L;

[0058] (3) Two steel sheets of identical size were degreased and pickled, then weighed, and then placed in two separate electroless nickel plating baths for 1 hour each, and weighed again. The weight gain of the steel sheet in the bath with added conditioning agent was calculated to be 0.96 compared to the weight gain of the steel sheet in the bath without added agent.

[0059] (4) Compared to the requirement that the plating rate decrease should not exceed 5%, the actual decrease was only 4%. Therefore, it was determined that the stabilizer and the conditioning agent had the same composition.

[0060] (5) Use two freshly prepared electroless nickel plating solutions, and add 200 mg / L of stabilizer to one of them. Use these two solutions to perform barrel plating on an equal number of small steel screws in a barrel plating tank, replacing the parts with a new batch every 2 hours, for a total of 8 hours of continuous plating.

[0061] (6) The results showed that the solution without stabilizer was obviously turbid and blackened, and dark-colored sediments were produced in the tank. However, the solution with stabilizer did not show the above phenomena, and there were no obvious sediments in the tank.

[0062] (7) Subsequently, 50 mg / L of stabilizer was added to the tank solution for each cycle, until the third cycle, when 30 mg / L of stabilizer was added per cycle. Then, until the fifth cycle, 15 mg / L of stabilizer was added per cycle. During this period, no turbidity or large amounts of black sediment appeared in the tank solution.

[0063] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for improving the stability of a bath for electroless nickel plating under barrel plating conditions, characterized by, The method includes the following steps: (1) Prepare a conditioning agent for plating solution conditioning; wherein: the conditioning agent is composed of ethoxylated propynyl alcohol and propoxylated propynyl alcohol in a molar ratio of 1:1; (2) Determine the usable lifespan of the electroless nickel plating bath and the plating rate on the substrate surface; wherein: the plating rate on the substrate surface includes V1 and V2; V1 is the plating rate of the electroless nickel plating bath under the production process conditions when the adjusting agent is added, and the amount of adjusting agent added is 200 mg / L; V2 refers to the plating rate of the electroless nickel plating bath under production process conditions without the addition of conditioning agents; (3) Prepare a stabilizer based on the plating rate measured in step (2); wherein: the stabilizer is composed of ethoxylated propynyl alcohol and propoxylated propynyl alcohol, or the stabilizer is composed of propynyl alcohol, ethoxylated propynyl alcohol and propoxylated propynyl alcohol; when V1 decreases by ≤5% compared to V2, the stabilizer is the same as the adjustment agent; when V1 decreases by >5% compared to V2, the stabilizer is prepared as follows: for every additional 1% decrease in plating rate, add 5% molar fraction of propynyl alcohol to the components of the adjustment agent, up to a maximum of 25% molar fraction of propynyl alcohol, to obtain the stabilizer; (4) Based on the ratio of the service life of the electroless nickel plating bath to its usable life, the stabilizer shall be added periodically. The amount of stabilizer added shall be determined by the ratio of the service life of the electroless nickel plating bath to its usable life. Specifically, the initial amount of stabilizer added to the electroless nickel plating bath is 200 mg / L, and then 50 mg / L shall be added every cycle. When the service life reaches 1 / 3 to 2 / 3 of the life, 30 mg / L shall be added every cycle. When the service life reaches 2 / 3 or more of the life, 15 mg / L shall be added every cycle.