阅读说明：本技术 一种在铝合金表面化学镀镍的方法 (Method for chemically plating nickel on surface of aluminum alloy ) 是由 庞美兴 曾文涛 于 2021-06-24 设计创作，主要内容包括：本发明涉及一种在铝合金表面化学镀镍的方法,包括如下步骤：步骤一,除油；步骤二,碱蚀；步骤三,去膜,将铝合金置于去膜溶液中浸渍60-180s；步骤四,一次浸锌,将铝合金置于浸锌溶液中浸渍30-90s；步骤五,退锌,将铝合金置于退锌溶液中浸渍30-90s,退锌溶液包括40-60ml/L的烷基磺酸、40-60g/L的过二硫酸钠；步骤六,二次浸锌,将铝合金置于浸锌溶液中浸渍25-35s；步骤七,制备纳米化学复合镀镍层；步骤八,制备电镀铜层；步骤九,再次制备纳米化学复合镀镍层；步骤十,化学镀镍。(The invention relates to a method for chemically plating nickel on the surface of an aluminum alloy, which comprises the following steps: step one, removing oil; step two, alkaline etching; step three, removing the film, namely soaking the aluminum alloy in a film removing solution for 60-180 s; step four, primary zinc dipping, namely putting the aluminum alloy into a zinc dipping solution to dip for 30-90 s; step five, removing zinc, namely putting the aluminum alloy into a zinc removing solution for soaking for 30-90s, wherein the zinc removing solution comprises 40-60ml/L of alkyl sulfonic acid and 40-60g/L of sodium peroxodisulfate; step six, secondary zinc dipping, namely putting the aluminum alloy into a zinc dipping solution to dip for 25-35 s; step seven, preparing a nano chemical composite nickel plating layer; step eight, preparing an electroplated copper layer; step nine, preparing the nano chemical composite nickel plating layer again; step ten, chemical nickel plating.)

1. A method for chemically plating nickel on the surface of an aluminum alloy is characterized by comprising the following steps:

step one, removing oil;

step two, alkaline etching;

step three, removing the film, namely soaking the aluminum alloy in a film removing solution for 60-180 s;

step four, primary zinc dipping, namely putting the aluminum alloy into a zinc dipping solution to dip for 30-90 s;

step five, removing zinc, namely soaking the aluminum alloy in a zinc removing solution for 30-90s, wherein the zinc removing solution comprises 40-60ml/L of alkyl sulfonic acid and 40-60g/L of sodium peroxodisulfate;

step six, secondary zinc dipping, namely putting the aluminum alloy into the zinc dipping solution to dip for 25-35 s;

preparing a nano chemical composite nickel plating layer, and electroplating the aluminum alloy in a nano chemical composite plating solution;

step eight, preparing an electroplating copper layer, and placing the aluminum alloy prepared with the nano-chemical composite nickel-plating layer into an electroplating copper solution for electroplating;

step nine, preparing the nano-chemical composite nickel-plating layer again, and putting the aluminum alloy with the prepared copper-plating layer into the nano-chemical composite plating solution for electroplating;

step ten, chemical nickel plating.

2. The method of claim 1, wherein: the aluminum alloy is cold-treated forged aluminum alloy, and the mass percent of Cu, Mg, Cr and Zn in the cold-treated forged aluminum alloy is not less than 1.2%, 2.0% and 5.0% respectively.

3. The method of claim 1, wherein: in the first step, ultrasonic oil removal is adopted for oil removal, after the aluminum alloy is soaked in an oil removal agent solution, ultrasonic waves with the frequency not less than 68KHZ are adopted for oil removal for 10-15min, and the oil removal agent solution comprises 10-30g/L of sodium carbonate, 10-30g/L of phosphate and 0.1-0.5g/L of surfactant.

4. The method of claim 1, wherein: in the second step, the alkaline etching is to clean the surface of the aluminum alloy for 30-90s by using an alkaline etching solution, wherein the alkaline etching solution comprises 10-30g/L of sodium hydroxide and no more than 1g/L of inorganic salt corrosion inhibitor.

5. The method of claim 1, wherein: the stripping solution comprises 50-100g/L ferric sulfate, 50-100g/L sulfuric acid and 5-10ml/L nitric acid.

6. The method of claim 1, wherein: the zinc dipping solution comprises 150-200g/L sodium hydroxide, 60-80g/L zinc oxide, 1-5g/L copper sulfate and 3-5g/L nickel sulfate.

7. The method of claim 1, wherein: the nano chemical composite plating solution comprises 5-10g/L of nickel sulfate and 5-10g/L of sodium hypophosphite, and the pH value of the nano chemical composite plating solution is 8.0-9.0.

8. The method of claim 7, wherein: in the seventh step, the electroplating time is 60-120s, and the electroplating current density is 2-3 ASD; in the ninth step, the electroplating time is 60-120s, and the electroplating current density is 0.1-0.2 ASD.

9. The method of claim 1, wherein: the copper electroplating solution comprises 15-20g/L of copper pyrophosphate, 200-300g/L of potassium pyrophosphate and no more than 1g/L of citrate, and the pH value of the copper electroplating solution is 8.0-9.0.

10. The method of claim 9, wherein: in the step eight, the electroplating time is 15-25min, and the electroplating current density is 0.4-0.1.0 ASD.

Technical Field

The invention relates to a metal material surface treatment technology, in particular to a method for chemically plating nickel on the surface of an aluminum alloy.

Background

Electroless plating requires no power source and relies on the catalytic reaction of a reducing agent in solution to release electrons to reduce metal ions to metal atoms. Electroless plating can form a metal plating layer on the surface of a metallic material or a non-metallic material. The chemical nickel plating of the aluminum-based material can improve the surface hardness, corrosion resistance, wear resistance, welding performance and magnetic performance of the aluminum-based material. The electrode potential of the aluminum is very negative, electrons are easy to lose, and the surface of the aluminum has a natural and compact oxide film, so that before chemical nickel plating is carried out on the aluminum-based material, an intermediate layer needs to be prepared on the surface of the aluminum-based material, thereby ensuring normal implementation of chemical plating and obtaining a plating layer with good bonding force.

At present, the process of chemical nickel plating of aluminum-based materials generally comprises the following steps: degreasing → etching → first zincating → nitric acid removing → second zincating → alkaline electroless nickel → normal electroless nickel, the aluminum-based material is used as the intermediate layer by the zinc layer obtained after the second zincating. The cold-treated wrought aluminum alloys contain components (Al, Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti) and component ratios which are greatly different from those of conventional aluminum alloys (e.g., duralumin alloy AI-Cu-Mg series, ultraduralumin alloy Al-Cu-Mg-Zn series, wrought aluminum alloy Al-Zn-Mg-Si series, etc.), and are suitable for surface treatment methods of aluminum or conventional aluminum alloys, and are not completely suitable for cold-treating wrought aluminum alloys. The technical scheme of the prior chemical nickel plating applied to aluminum or traditional aluminum alloy is applied to cold treatment of forged aluminum alloy, and has the following technical problems:

1. the thickness of a zinc layer obtained after the cold-treated forged aluminum alloy is subjected to secondary zinc immersion is extremely thin, and the binding force between the zinc layer and the cold-treated forged aluminum alloy is poor; 2. when the cold-processed forged aluminum alloy is subjected to secondary zinc dipping and then is subjected to chemical nickel plating, the nickel-phosphorus alloy is not plated on the surface of the cold-processed forged aluminum alloy, the zinc dipping layer is almost completely dissolved, and the chemical nickel plating solution is poisoned; 3. the nickel-phosphorus alloy is difficult to be directly plated on the surface of the cold-processed forging aluminum alloy, so that after the zinc dipping layer is dissolved, the chemical nickel plating solution can corrode the matrix of the cold-processed forging aluminum alloy.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention provides a method for chemically plating nickel on the surface of an aluminum alloy, the aluminum alloy recorded in the invention is cold-treated forged aluminum alloy, the strength of the cold-treated forged alloy is superior to that of mild steel, and the mass percent of Cu, Mg, Cr and Zn in the cold-treated forged aluminum alloy is not less than 1.2%, 2.0% and 5.0% respectively.

The invention adopts the following technical scheme: a method for chemically plating nickel on the surface of an aluminum alloy specifically comprises the following steps:

removing oil for not less than 10min, thereby removing oil stains on the surface of the aluminum alloy and obtaining a surface with strong activity;

secondly, performing alkaline etching, namely cleaning the surface of the aluminum alloy subjected to ultrasonic oil removal for no less than 30s by using an alkaline etching solution, and removing an original compact oxide film on the surface of the aluminum alloy by using the alkaline etching solution, so that a fresh aluminum alloy surface is exposed;

step three, stripping, namely soaking the aluminum alloy in a stripping solution for 60-180s, wherein the stripping solution comprises 50-100g/L ferric sulfate, 50-100g/L sulfuric acid and 5-10ml/L nitric acid, and the step is to reduce the aluminum oxide on the surface of the aluminum alloy through the reducibility of ferric ions in the stripping solution to expose a fresh aluminum alloy surface;

step four, primary zinc dipping, namely putting the aluminum alloy into a zinc dipping solution for dipping for 30-90s, wherein the zinc dipping solution comprises 150-200g/L sodium hydroxide, 60-80g/L zinc oxide, 1-5g/L copper sulfate and 3-5g/L nickel sulfate, and a layer of relatively fine zinc layer is replaced on the surface of the fresh aluminum alloy through the primary zinc dipping;

step five, removing zinc, namely, putting the aluminum alloy into a zinc removing solution for soaking for 30-90s, wherein the zinc removing solution comprises 40-60ml/L of alkyl sulfonic acid and 40-60g/L of sodium peroxodisulfate, and the synergistic action of the sodium peroxodisulfate with strong oxidizing property and the alkyl sulfonic acid (organic strong acid) in the zinc removing solution is utilized to stably and slowly remove the zinc layer on the surface of the aluminum alloy;

step six, secondary zinc dipping, namely putting the aluminum alloy into a zinc dipping solution for dipping for 25-35s, wherein the composition of the zinc dipping solution used in the step four is the same as that of the zinc dipping solution used in the step four, and a fine-crystalline zinc layer is deposited on the surface of the aluminum alloy subjected to zinc removal through the secondary zinc dipping;

preparing a nano chemical composite nickel plating layer, putting an aluminum alloy into a nano chemical composite plating solution for plating for 60-120s, wherein the current density is 2-3ASD, the nano chemical composite plating solution comprises 5-10g/L nickel sulfate and 5-10g/L sodium hypophosphite, the pH value of the nano chemical composite plating solution is 8.0-9.0, the aluminum alloy needs to be put into the nano chemical composite plating solution with electricity to prevent the zinc displacement from being separated out to influence the binding force, and a nonmagnetic plating layer can be obtained in the step;

step eight, preparing an electroplated copper layer, namely putting the aluminum alloy prepared with the nano-chemical composite nickel-plated layer into an electroplated copper solution for plating for 15-25min, wherein the current density is 0.4-0.1.0ASD, the electroplated copper solution comprises 15-20g/L of copper pyrophosphate, 200-300g/L of potassium pyrophosphate and citrate not more than 1g/L, the pH value of the electroplated copper solution is 8.0-9.0, and the potential difference between the nano-chemical composite nickel-plated layer and the copper layer can be improved by preparing the electroplated copper layer, so that the corrosion resistance is improved;

step nine, preparing a nano-chemical composite nickel plating layer again, putting the aluminum alloy with the copper plating layer into a nano-chemical composite plating solution for plating for 60-120s, wherein the current density is 0.1-0.2ASD, the composition of the nano-chemical composite plating solution used in the step seven is the same as that of the nano-chemical composite plating solution used in the step seven, the nano-chemical composite nickel plating layer is prepared on the copper plating layer to replace activated palladium, and the problem that the chemical nickel cannot be directly plated on the copper plating layer is solved, so that a nonmagnetic plating layer is obtained while the cost is reduced;

and step ten, chemically plating nickel, namely plating a nickel-phosphorus alloy layer on the surface of the beryllium-aluminum alloy by using a chemical nickel plating method, thereby preparing a nonmagnetic plating layer.

And deionized water is used for cleaning the surface of the aluminum alloy between each step.

In one embodiment, the degreasing agent solution in the first step comprises 10-30g/L of sodium carbonate, 10-30g/L of phosphate and 0.1-0.5g/L of surfactant.

In one embodiment, the alkaline etching solution in the second step comprises 10-30g/L of sodium hydroxide and no more than 1g/L of inorganic salt corrosion inhibitor.

In an embodiment, the electroless plating solution used in the ninth step includes 4-6g/L of nickel sulfate, 20-25g/L of sodium hypophosphite, no more than 1g/L of citric acid, and no more than 1g/L of malic acid, and the pH of the electroless plating solution is 4.6-5.2, and the aluminum alloy is placed into the electroless plating solution for plating, so as to obtain the electroless nickel-phosphorus alloy layer after the plating thickness requirement is met.

In one embodiment, the electroless plating solution used in the ninth step includes 10-30g/L of nickel salt, 10-35 g/L of sodium hypophosphite, 5-25 g/L of complexing agent, 3-15 g/L of buffering agent, 0.5-10 g/L of activating agent and 10-200 mg/L of stabilizing agent, the temperature of the electroless plating solution is 60-90 ℃, the aluminum alloy is placed into the electroless plating solution for plating, and the electroless nickel-phosphorus alloy plating layer is obtained after the requirement of the plating layer thickness is met.

When the cold treatment of the forged aluminum alloy simultaneously satisfies the conditions that the mass percent of Cu is not less than 1.2%, the mass percent of Mg is not less than 2.0%, the mass percent of Cr is not less than 0.18%, and the mass percent of Zn is not less than 5.0%, the aluminum alloy can not be subjected to secondary zinc dipping treatment to prepare a zinc layer with good bonding force, although the principle of the aluminum alloy is not clearly researched, the result can cause the aluminum alloy to be incapable of being subjected to chemical nickel plating, and therefore the primary problem to be solved for realizing the chemical nickel plating of the aluminum alloy is to prepare a zinc layer with good bonding force and compactness on the surface of the aluminum alloy. The technical scheme of the invention is that a dense zinc layer with good bonding force is prepared on the surface of the aluminum alloy by combining a pretreatment (ultrasonic oil removal, alkali etching and film removal) process and a zinc immersion process. The binding force between the prepared zinc layer and the aluminum alloy can be improved when the aluminum alloy subjected to the pretreatment is subjected to primary zinc dipping, but the applicant finds that the alloy elements of Cu, Cr, Zn and Mg in the aluminum alloy can have adverse effects on the formation of the zinc layer, namely the zinc layer formed on the surface of the aluminum alloy at the beginning is dense and has good binding force, but the formed zinc layer is in a loose porous structure along with the increase of the thickness of the zinc layer. Therefore, the zinc stripping is required after the primary zinc dipping, namely, the zinc layer with a loose porous structure close to the outer side is removed, and a dense zinc layer with good bonding force with the aluminum alloy is left. After the zinc is removed, when the aluminum alloy is subjected to secondary zinc dipping, because the alkyl sulfonic acid can selectively adsorb certain crystal faces on the surface of the zinc layer left after the zinc is removed, the discharge speed of metal zinc ions during the secondary zinc dipping is reduced, the growth speed of certain crystal faces is inhibited, and thus the crystal grains of the metal zinc deposition layer are refined, and the zinc layer with fine crystals is formed.

Since the alloy elements of Cu, Cr, Zn, and Mg in the aluminum alloy cause a change in the potential of the zinc layer on the surface, if the aluminum alloy subjected to the secondary zinc dipping is directly put into the electroless plating solution, the zinc layer is rapidly dissolved, and the nickel-phosphorus alloy plating cannot be performed. In order to solve the technical problem, the technical scheme of the invention is to prepare three laminated coating layers (a nano chemical composite nickel coating layer, a copper coating layer and a nano chemical composite nickel coating layer from inside to outside in sequence) on the surface of a zinc layer of an aluminum alloy, wherein the surface of the zinc layer of the aluminum alloy is fine in crystallization and the binding force of the zinc layer and the aluminum alloy is excellent, so that the condition of preparing the nano chemical composite nickel coating layer on the surface of the zinc layer is provided, and the zinc layer is physically isolated by preparing the three coating layers, so that the aluminum alloy can prepare a nonmagnetic nickel-phosphorus alloy layer with thicker thickness and good binding force in a chemical plating solution.

In summary, compared with the prior art, the invention has at least the following beneficial effects:

1. the method for chemically plating nickel on the surface of the aluminum alloy is suitable for cold treatment of forged aluminum alloy and is also suitable for aluminum or traditional aluminum alloy;

2. the invention has the technical problem that the cold treatment has poor binding force between the surface of the forged aluminum alloy and the zinc layer prepared by zinc dipping;

3. when the nano-chemical composite nickel-plating layer is prepared, the plating layer is more uniform and compact and has more excellent corrosion resistance and wear resistance by improving the component proportion and the plating parameters of the plating solution.

4. The invention reasonably utilizes the electrochemical characteristics and the structural characteristics of the nano chemical composite nickel plating layer, the copper plating layer and the chemical nickel-phosphorus plating alloy layer, designs the multilayer composite plating layer with excellent corrosion resistance according to the sacrificial anode principle, the corrosion resistance of the multilayer composite plating layer can resist neutral salt fog for more than 1000 hours, and the multilayer composite plating layer is uniform, compact, corrosion resistant, wear resistant and non-magnetic, and can ensure that the aluminum alloy has long service life in a severe corrosion environment or a strong magnetic field environment.

Detailed Description

It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The aluminum alloy described in this example is a cold-processed forged aluminum alloy, and more specifically, the cold-processed forged aluminum alloy is 7075 aluminum alloy. The 7075 aluminum alloy comprises the following components in percentage by mass: 0.40% of Si; 0.50% Fe; 1.2-2.0% Cu; 0.30% Mn; 2.1-2.9% Mg; 0.18-0.28% Cr; 5.1-6.1% Zn; 0.20% of Ti; the balance being Al.

In the present invention, since the nickel plating layer prepared by an aluminum alloy in an electroless nickel plating solution contains phosphorus, for more accurate description, the electroless nickel plating layer is described as an electroless nickel-phosphorus alloy layer, and thus the electroless nickel-phosphorus alloy layer described in the present invention is equivalent to the electroless nickel plating layer.

The embodiment provides a method for chemically plating nickel on the surface of an aluminum alloy, which specifically comprises the following steps:

step one, ultrasonic oil removal, namely, after an aluminum alloy is immersed in an oil removal agent solution, ultrasonic oil removal is carried out for 10-15min by adopting frequency not less than 68KHZ, the oil removal agent solution comprises 10-30g/L of sodium carbonate, 10-30g/L of phosphate and 0.1-0.5g/L of surfactant, and preferably, the surfactant is sodium dodecyl benzene sulfonate;

secondly, performing alkaline etching, namely cleaning the surface of the aluminum alloy subjected to ultrasonic oil removal for 30-90s by using an alkaline etching solution, wherein the alkaline etching solution comprises 10-30g/L of sodium hydroxide and no more than 1g/L of inorganic salt corrosion inhibitor, and the inorganic salt corrosion inhibitor is one or a mixture of chromate, phosphate, zinc sulfate, silicate, molybdate and tungstate;

step three, removing the film, namely soaking the aluminum alloy in a film removing solution for 60-180s, wherein the film removing solution comprises 50-100g/L ferric sulfate, 50-100g/L sulfuric acid and 5-10ml/L nitric acid;

step four, primary zinc dipping, namely putting the aluminum alloy into a zinc dipping solution for dipping for 30-90s, wherein the zinc dipping solution comprises 150-200g/L sodium hydroxide, 60-80g/L zinc oxide, 1-5g/L copper sulfate and 3-5g/L nickel sulfate;

step five, removing zinc, namely putting the aluminum alloy into a zinc removing solution for soaking for 30-90s, wherein the zinc removing solution comprises 40-60ml/L of alkyl sulfonic acid and 40-60g/L of sodium peroxodisulfate;

step six, secondary zinc dipping, namely putting the aluminum alloy into a zinc dipping solution for 30s of dipping, wherein the composition of the zinc dipping solution used in the step four is the same as that of the zinc dipping solution used in the step four;

seventhly, preparing a nano chemical composite nickel plating layer, putting the aluminum alloy into a nano chemical composite plating solution for plating for 60-120s, wherein the current density is 2-3ASD, the nano chemical composite plating solution comprises 5-10g/L of nickel sulfate and 5-10g/L of sodium hypophosphite, the pH value of the nano chemical composite plating solution is 8.0-9.0, and the aluminum alloy needs to be charged and put into the nano chemical composite plating solution;

step eight, preparing an electroplated copper layer, namely putting the aluminum alloy prepared with the nano-chemical composite nickel-plated layer into an electroplated copper solution for plating for 15-25min, wherein the current density is 0.4-0.1.0ASD, the electroplated copper solution comprises 15-20g/L of copper pyrophosphate, 200-300g/L of potassium pyrophosphate and no more than 1g/L of citrate, and the pH value of the electroplated copper solution is 8.0-9.0;

step nine, preparing the nano chemical composite nickel plating layer again, putting the aluminum alloy into the nano chemical composite plating solution for plating for 60-120s, wherein the current density is 0.1-0.2ASD, and the composition of the nano chemical composite plating solution used in the step seven is the same as that of the nano chemical composite plating solution used in the step seven;

and step ten, chemically plating nickel, namely plating a nickel-phosphorus alloy layer on the surface of the beryllium-aluminum alloy by using a chemical nickel plating method, and using an acidic low-phosphorus, medium-phosphorus and high-phosphorus chemical nickel plating solution.

In this embodiment, the thicknesses of the nano-electroless composite nickel-plated layer, the copper-plated layer and the electroless nickel-phosphorus alloy-plated layer can be reasonably selected according to the corrosion conditions of the aluminum alloy in different use environments, each plating layer can be thicker if the corrosion environment is harsh, and each plating layer can be thinner if the corrosion environment is relatively mild. The above steps require washing with deionized water after each step is completed.

In this embodiment, the multi-layer composite plating layer prepared on the surface of the aluminum alloy is a silver-white metal surface, preferably, the thicknesses of the two nano-chemical composite nickel plating layers are both 5 μm, the thickness of the copper plating layer is 20 μm, and the thickness of the chemical nickel-phosphorus plating alloy layer is 10 μm, at this time, the multi-layer composite plating layer can resist the salt spray test for more than 1000 hours. And testing the binding force of the plating layer by adopting a grid cutting method, wherein the layer composite plating layer on the surface of the aluminum alloy does not fall off, and the rating is 0 grade.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.