CN112126929A

CN112126929A - Local gold plating process for surface of aluminum material

Info

Publication number: CN112126929A
Application number: CN202011028011.2A
Authority: CN
Inventors: 张宇; 於杨强; 肖登华; 廖孟良; 汪朝晖
Original assignee: Shenzhen Haili Surface Technology Treatment Co ltd
Current assignee: Shenzhen Haili Surface Technology Treatment Co ltd
Priority date: 2020-09-26
Filing date: 2020-09-26
Publication date: 2020-12-25

Abstract

The application relates to the field of gold plating technology, in particular to an aluminum surface local gold plating process, which comprises the following steps: removing impurities from the surface of the aluminum material; b, immersing the aluminum material treated in the step A into a zinc dipping solution, reacting until a zinc coating is formed on the surface of the aluminum material, and then washing with water; b, immersing the aluminum material subjected to zinc dipping in the step B into nickel plating solution, reacting until a nickel plating layer is formed on the surface of the aluminum material, and washing with water; c, immersing the aluminum material plated with the nickel in the step C into a gold plating solution, reacting until a gold plating layer is formed on the surface of the aluminum material, washing with water, and drying; d, dividing the surface of the aluminum material plated with gold in the step D into a gold-plated area and a non-gold-plated area, and wrapping a layer of shielding material on the surface of the gold-plated area; and immersing the partially shielded aluminum material into the gold stripping mixed solution, reacting until a gold plating layer of a non-gold-plating area of the aluminum material disappears, washing with water after a nickel plating layer is completely exposed, and drying to obtain a partially gold-plated part. The method has the effect of improving the binding force between the plating layer and the plated part.

Description

Local gold plating process for surface of aluminum material

Technical Field

The application relates to the field of gold plating technology, in particular to a local gold plating process for the surface of an aluminum material.

Background

With the rapid development of science and technology, aluminum products are more and more widely applied in the industries of aerospace, automobiles, instruments, electronics and the like. Since aluminum is a relatively active metal, its application is usually surface-functionalized. Among them, electroplating is one of the important means for surface treatment of aluminum materials, that is, treatment or modification of the surface of aluminum materials by electrochemical methods, and the purpose of the method is to change the surface properties or dimensions of substrates by plating a metal plating layer on the aluminum materials. Since the gold-plated layer has high corrosion resistance, good conductivity, high temperature resistance and easy soldering, the gold-plated layer is widely used on aluminum materials. However, gold is a relatively expensive metal, and in practice, a local gold plating method is often used to reduce the cost.

In the related local gold plating process of the aluminum material, the aluminum alloy is difficult to plate, because the aluminum has strong electronegativity and strong affinity to oxygen, the surface of the aluminum alloy is easy to combine with oxygen to generate an oxide film, the oxide film has a compact structure, and the gold-plated layer plated on the aluminum material is easy to fall off, so the method of plating the gold layer on the aluminum material after plating the zinc layer on the aluminum material is generally adopted, but even if the method of combining the zinc layer with the gold-plated layer is used, the bonding force between the aluminum material and the gold-plated layer is poor.

Disclosure of Invention

In order to improve the binding force between the gold-plated layer and the aluminum material, the application provides a local gold-plating process for the surface of the aluminum material.

The application provides an aluminum product surface local gold plating technology adopts following technical scheme:

a local gold plating process for the surface of an aluminum material is characterized by comprising the following steps: the method comprises the following steps:

a, surface treatment: removing impurities from the surface of the aluminum material;

b, zinc dipping: b, immersing the aluminum material treated in the step A into a zinc dipping solution, reacting until a zinc coating is formed on the surface of the aluminum material, and then washing with water;

c, nickel plating: b, immersing the aluminum material subjected to zinc dipping in the step B into nickel plating solution, reacting until a nickel plating layer is formed on the surface of the aluminum material, and washing with water;

d, gold plating: c, immersing the aluminum material plated with the nickel in the step C into a gold plating solution, reacting until a gold plating layer is formed on the surface of the aluminum material, washing with water, and drying;

e, local shielding: d, dividing the surface of the aluminum material plated with gold in the step D into a gold-plated area and a non-gold-plated area according to requirements, and wrapping a layer of shielding material on the surface of the gold-plated area;

f, gold removing: and immersing the partially shielded aluminum material into the gold stripping mixed solution, reacting until a gold plating layer of a non-gold-plating area of the aluminum material disappears, washing with water after a nickel plating layer is completely exposed, and drying to obtain the partially gold-plated aluminum material.

By adopting the technical scheme, the surface treatment is mainly used for removing impurities such as oxides, other metal impurities and oil stains on the surface of the aluminum material, so that the surface of the aluminum material reaches a higher cleanliness level, and the surface of the aluminum material is in an activated state, thereby improving the binding force of the aluminum material and a subsequent coating.

The zinc dipping step is mainly to replace a zinc dipping layer on the surface of the aluminum material, and when other metals are plated on the aluminum material, the zinc dipping layer can be used as an intermediate layer between the aluminum material and other plating layers so as to enhance the bonding force between the aluminum material and the subsequent plating layers. The reasons for this may be: because zinc exists in the form of complex ions in the alkaline solution, the potential of the zinc is lower than that of the zinc in a common solution (such as an iron salt solution or a nickel salt solution), when the aluminum material is immersed in the zinc immersion liquid, a thin and uniform zinc immersion layer can be obtained, and therefore good binding force between the aluminum material and a subsequent coating is ensured. The reason for this may also be: the aluminum has strong ductility and permeability, and if the aluminum is directly plated with gold, the color of the aluminum can permeate out after the aluminum is placed for a period of time, so that the surface of the aluminum is discolored.

After the step of zinc dipping, a nickel plating step is needed for improving the binding force between the subsequent gold plating layer and the aluminum material, and the brazing effect between the aluminum materials can be improved when brazing is needed after the aluminum materials are subjected to local gold plating. The reasons may be due to a combination of one or more of the following reasons: firstly, although a uniform zinc layer is deposited on the surface of the aluminum material, the zinc layer can still be dissolved in a strong acid or strong alkaline medium, and in order to ensure the binding force of a plating layer, a nickel plating step is required after the zinc dipping step; secondly, the wear resistance can be improved, and the bonding force of gold plating after bottoming by using a nickel layer is avoided when the gold plating is directly carried out on the aluminum material or the aluminum material with the zinc dipping layer on the surface is carried out; thirdly, most of the aluminum materials after being partially plated with gold need to be brazed with other parts, and a nickel plating layer is used for improving the brazing performance in the brazing process.

And plating a gold layer on the aluminum material through a gold plating step, wrapping a layer of shielding material in a gold plating area, and putting the aluminum material into the mixed solution of the gold stripping solution to remove the gold plating layer on the non-gold plating area and keep the gold plating layer on the gold plating area, thereby obtaining the local gold-plated aluminum material.

Preferably, the surface treatment in step a comprises the following specific processes: placing the aluminum material in a nitric acid solution for pickling and then washing with water, then placing the aluminum material in an alkali solution for alkali etching and then washing with water, and finally placing the aluminum material in a descaling solution for descaling and then washing with water.

By adopting the technical scheme, the surface treatment is a key step of plating a gold layer on the aluminum material, the aluminum material is firstly pickled by nitric acid solution, other metal impurities on the surface of the aluminum material can be removed, and an oxidation film which is relatively compact on the surface of the aluminum material is loosened, so that the cleaning effect of the post-process on the surface of the aluminum material is increased, and the higher cleanliness is achieved. The alkaline etching step is mainly used for removing oil stains on the surface of the aluminum material, and finally, impurities and dirt remained on the surface of the aluminum material are further cleaned through descaling liquid, so that the aluminum material is exposed out of the surface rich in aluminum.

Preferably, the concentration of the nitric acid solution is 40-60% by volume, the alkali solution is a sodium hydroxide solution with the concentration of 80-120g/L, the descaling solution is a mixed solution containing a descaling agent, nitric acid, phosphoric acid and an activating salt, wherein the descaling agent accounts for 10-20% by volume of the descaling solution, the nitric acid accounts for 20-30% by volume of the descaling solution, the phosphoric acid accounts for 40-60% by volume of the descaling solution, and the activating salt accounts for 40-200g/L in the descaling solution.

By adopting the technical scheme, when the volume percentage concentration of the nitric acid solution is more than 60%, the oxide on the surface of the aluminum material cannot be removed, the passivation reaction is continuously carried out on the surface of the aluminum material to generate a compact oxide film, and when the volume percentage concentration of the nitric acid solution is less than 40%, the removing force on the surface of the aluminum material is insufficient, so that the cleanliness of the surface of the aluminum material cannot reach the subsequent process standard; similarly, if the concentration of the sodium hydroxide solution is too high, the reaction time is difficult to control, and the aluminum material is easy to damage, and if the concentration of the sodium hydroxide solution is too low, the reaction force is insufficient, and impurities are difficult to clean; the mixed solution containing 10-20% of scale remover, 20-30% of nitric acid, 40-60% of phosphoric acid and 40-200g/L of activating salt is used, and the scale removing effect on the aluminum material is better.

In addition, the descaling agent in the application can be selected from YD-606 type descaling agent sold by Hippon and Hippon environmental protection science and technology Limited, AZ-5021 type descaling agent sold by Shanghai' an bamboo industry Limited, AL-55 type descaling agent sold by Autejia science and technology Limited in Shenzhen, and the like with the same or similar properties, and the activated salt can be S-CU-2 type activated acid salt sold by Shunxin benefit chemical industry Limited in Quanzhou, APN type activated acid salt sold by Taide chemical industry Limited in Zhejiang Xinjiang, AL-50 type activated salt sold by Autejia science and technology Limited in Shenzhen.

Preferably, the zinc dipping process in the step B comprises the following specific steps: and C, immersing the aluminum material subjected to surface treatment in the step A into a first zinc dipping solution for reaction, then washing with water, immersing the aluminum material into a zinc removing solution for reaction, then washing with water, and finally immersing the aluminum material into a second zinc dipping solution for reaction, and then washing with water.

By adopting the technical scheme, the galvanized layer obtained on the aluminum material by the first zinc dipping is looser, and the better binding force between the aluminum material and the galvanized layer can not be ensured. Therefore, the zinc dipping step of the method comprises two times of zinc dipping, firstly, through a first zinc dipping process, on one hand, an oxide film possibly remaining after the surface treatment of the aluminum material can be further removed, on the other hand, a loose zinc layer is preliminarily formed on the aluminum material, then, the aluminum material is dipped in nitric acid for zinc stripping, the poor zinc layer is removed, and the exposed surface after the zinc stripping provides a good condition for the second zinc dipping, so that the surface of the aluminum material is fully activated, and a good bonding force between the aluminum material and the zinc layer is ensured.

Preferably, the first zinc dipping solution and the second zinc dipping solution are mixed solution containing 30-50% of zinc oxide, 20-40g/L of sodium hydroxide and 2-6g/L of potassium cyanide; the zinc stripping solution is a nitric acid solution with the volume percentage concentration of 40-60%.

By adopting the technical scheme, experiments show that the binding force of the plating layer can be improved by properly increasing the alkali consumption, but when the alkali consumption is too high, a perfect zinc layer is not easy to deposit at the bending part or blind hole of the aluminum material due to the higher viscosity of the alkali, so that the binding force of the zinc plating layer at the bending part or blind hole is reduced. The cyanide plays a complexing role in the zinc dipping process, so that zinc ions can be deposited on the surface of the aluminum material, the zinc coating is fine and smooth, and the quality of the zinc coating is improved.

Preferably, the reaction time of the first zinc dipping is 30-50s, the reaction time of the zinc stripping is 15-30s, and the reaction time of the second zinc dipping is 15-20 s.

By adopting the technical scheme, tests show that the quality of the plating layer obtained in the three steps in the corresponding reaction time is better; the reason for this may be: when the reaction time of the first zinc dipping exceeds 50s, the zinc coating on the aluminum material is easy to be too thick, the problem of poor confidentiality exists in the too thick zinc coating, and when the reaction time of the zinc stripping is shorter than 30s, the incomplete zinc coating is easy to occur; similarly, the reason for the second zincating is similar to that of the first zincating; when the reaction time of the dezincification exceeds 30 seconds, the reaction is likely to be excessive, new oxides are formed on the surface of the aluminum material, and the normal operation of the second zinc dipping is affected, and when the reaction time of the dezincification is shorter than 15 seconds, the problem of incomplete dezincification is likely to occur.

Preferably, the specific process of nickel plating in the step C is as follows: and C, putting the aluminum material subjected to zinc dipping in the step B into an alkaline nickel solution for reaction, washing with water, putting the aluminum material into a chemical nickel plating solution with the pH of 4.6-5 for reaction, washing with water, and finally putting the aluminum material into the electrolytic nickel plating solution for reaction and washing with water.

Preferably, the alkaline nickel solution is mainly an aqueous solution containing 120ml/L sodium hypophosphite and 70ml/L nickel salt; the chemical nickel plating solution is mainly an aqueous solution containing 120ml/L sodium hypophosphite and 50ml/L nickel salt; the nickel electroplating solution is a mixed solution containing 40-70g/L of nickel amide, 30-50g/L of nickel chloride and 35-45g/L of boric acid.

Through adopting above-mentioned technical scheme, the aluminum product passes through alkali nickel earlier, at the preliminary nickel coating that forms in the aluminum product surface, passes through chemical nickel plating again, can form the comparatively even nickel coating of one deck on the aluminum product surface, and the cohesion between nickel coating that obtains through chemical nickel plating and the aluminum product is higher, through electronickelling at last, further forms the nickel coating on the aluminum product to further strengthen the cohesion between nickel coating and the aluminum product. Wherein the nickel salt provides nickel in the reaction, and the nickel salt can be nickel sulfate, nickel halide or a nickel complex.

Preferably, the reaction time of the alkali nickel is 4-6min, the reaction time of the chemical nickel plating is 35-50min, and the reaction time of the electroplating nickel is 7-12 min.

By adopting the technical scheme, experiments show that the nickel plating layer with better quality can be obtained in the steps within the corresponding reaction time range, and the reason is probably that: the reaction time of the alkali nickel is between 4 and 6min, and a nickel layer with moderate plating thickness can be obtained, so that conditions are provided for subsequent chemical nickel plating. If the reaction time of electroless nickel plating and electroplating nickel exceeds the corresponding time, the nickel layer on the aluminum material is easily too thick, the problem of poor fineness exists in the too thick nickel layer, and if the reaction time of electroless nickel plating and electroplating nickel is shorter than the corresponding time, the incomplete nickel plating is easily caused.

Preferably, the gold plating in step D comprises the following specific processes: and C, immersing the aluminum material plated with nickel in the step C into a gold pre-plating solution at 45-60 ℃ for electroplating for 1-2min, then washing with water, immersing the aluminum material into a thick gold plating solution at 55-60 ℃ for electroplating for 6-8min, washing with water and drying.

Preferably, the pre-gold plating solution is an aqueous solution containing 0.8-2g/L of pure gold cylinder opener; the thick gold plating solution is an aqueous solution containing 1.5-2.5g/L of pure gold cylinder opener.

By adopting the technical scheme, before the thick gold plating solution is plated, a small amount of pure gold open-cylinder agent is used for pre-plating gold, on one hand, the binding force between the pre-plating gold layer and the aluminum material is improved, the porosity of the gold plating layer is reduced, and on the other hand, the plating solution is protected, and the pollution is reduced. Through the thick gold plating step, a layer of fine and smooth gold plating layer can be obtained on the aluminum material. Wherein, the pure gold opener can be AEGOLD CC-303M type opener of Taiyuan Citian fine chemical engineering Limited company, Shenzhen Dunn and AUDOULLON F320 type opener sold by metal surface science and technology Limited company, and other products with the same or similar properties on the market.

Preferably, the voltage in the pre-gold plating step is 2-2.4V; the current density in the thick gold plating step is 0.2-0.3 ASD.

By adopting the technical scheme, experiments show that when the voltage is controlled within 2-2.4V in the pre-gold plating step, the bonding force of the plating layer obtained on the aluminum material is higher, and similarly, when the current density is controlled within 0.2-0.3ASD in the thick gold plating step, the bonding force of the plating layer obtained on the aluminum material is higher.

Preferably, in the local shielding step, a shielding jig is attached to the surface of the gold-plated area to wrap a layer of shielding material, or shielding paint is coated on the surface of the gold-plated area to wrap a layer of shielding material.

By adopting the technical scheme, the shielding jig is attached to the gold plating area or the shielding paint is coated on the gold plating area, the two modes can shield the place needing the gold plating layer in the gold stripping process, and the gold layer which is not coated with the shielding material area can be dissolved in the gold stripping liquid, so that the effect of local gold plating is achieved. Wherein the shielding paint is specifically an epoxy primer or a water-based primer-topcoat coating.

Preferably, in the local shielding step, a shielding jig is attached to the gold-plated area to wrap a layer of shielding material, the shielding jig includes two corresponding attached patches, one of the two corresponding patches has an insertion post, and the other patch has an insertion hole for inserting the insertion post.

Through adopting above-mentioned technical scheme, when needs carry out local plating, two pasters laminate respectively on the both sides face of aluminum product, because the gold-plated district of aluminum product has the through-hole, two pasters paste respectively on the both sides of gold-plated district, insert the post on one of them paster and pass the through-hole and insert and arrange in the jack of another paster to can shelter from the place that needs the gold layer, easy dismounting. Compared with the shielding paint coating, the shielding paint coating method has the advantages that the paint coating on one product takes about 10 minutes, the shielding jig is only used for 1 minute, and the processing efficiency is greatly improved. In addition, after the shielding paint is used, the shielding paint needs to be removed completely, and the jig is taken out, so that the efficiency is further improved, and the cost is saved. In addition, the shielding jig is environment-friendly and odorless.

Preferably, the shielding jig is a plastic product.

Through adopting above-mentioned technical scheme, plastic products's tool can be acidproof and alkali-resisting, and its compliance is good, can not scratch cladding material.

Preferably, after the step F, there is a step of protecting the partially gold-plated aluminum material, and the specific steps are as follows: at 35-45 deg.c, the local gold-plated aluminum material is first set in water solution of Kangli sheet in the concentration of 0.1-0.2 vol% for reaction for 5-15 sec before water washing.

By adopting the technical scheme, the color change of the gold plating layer on the aluminum material is mainly prevented from being oxidized too fast.

In summary, the present application at least includes the following beneficial technical effects:

1. firstly, carrying out surface treatment on the aluminum material to enable the aluminum material to reach a higher clean level, and then plating a zinc coating on the surface of the aluminum material to be used as an intermediate layer between the aluminum material and a subsequent coating so as to enhance the bonding force between the aluminum material and the subsequent coating; then plating a nickel plating layer on the aluminum material for improving the binding force between the plating layer and the aluminum material, and improving the brazing effect between the aluminum materials when the brazing is needed after the local gold plating of the aluminum material is finished; plating a gold plating layer on the aluminum material, wrapping a layer of shielding material in the gold plating area, putting the aluminum material into the mixed solution of the gold stripping solution, removing the gold plating layer on the non-gold plating area, and reserving the gold plating layer on the gold plating area, thereby obtaining the local aluminum plating material with better plating layer bonding force;

2. the surface of the aluminum product is pickled by nitric acid, so that other metal impurities on the surface of the aluminum product can be removed, a relatively compact oxide film on the surface of the aluminum product is loosened, and the cleaning effect of a subsequent process is improved;

3. according to the method, through the twice zinc dipping process, on one hand, an oxide film possibly remaining after surface treatment can be further removed, on the other hand, a loose zinc layer is formed on the aluminum material, then the aluminum material is dipped in nitric acid for zinc stripping, the poor zinc layer is removed, and the exposed surface after zinc stripping provides a good condition for secondary zinc dipping, so that the surface of the aluminum material is fully activated, good binding force between the aluminum material and the zinc layer is ensured, secondary zinc dipping is performed on the aluminum material after zinc stripping, and a zinc coating with good quality can be obtained on the aluminum material.

Detailed Description

The present application will be described in further detail with reference to examples.

The source of the lotion used in all examples and comparative examples is shown in table 1 below:

TABLE 1 sources of the lotions

Example 1

A local gold plating process for the surface of an aluminum material is obtained by sequentially carrying out the following steps:

a, surface treatment: putting oil removal powder into an ultrasonic wave tank, placing the aluminum material into the ultrasonic wave tank to remove oil for 0.5min, then washing with water, then placing the aluminum material into a sodium hydroxide solution with the concentration of 120g/L to react for 2min at 35 ℃, finally placing the aluminum material into a descaling solution to react for 2min, and then washing with water, wherein the descaling solution is a mixed solution containing a descaling agent, nitric acid, phosphoric acid and an activating salt, the descaling agent accounts for 10% of the descaling solution by volume percentage, the nitric acid accounts for 30% of the descaling solution by volume percentage, the phosphoric acid accounts for 40% of the descaling solution by volume percentage, and the activating salt accounts for 40g/L of the descaling solution.

B, zinc dipping: and B, immersing the aluminum material subjected to the surface treatment in the step A into a first zinc dipping solution, reacting for 30s, and washing with water, wherein the first zinc dipping solution is a mixed solution containing 50% of zinc oxide, 40g/L of sodium hydroxide and 6g/L of potassium cyanide.

C, nickel plating: and C, putting the aluminum material subjected to zinc dipping in the step B into an alkaline nickel solution for reacting for 6min, washing with water, then putting the aluminum material into a chemical nickel plating solution with the pH value of 4.6 at 83 ℃ for reacting for 35min, and washing with water, wherein the alkaline nickel solution is an aqueous solution containing 120ml/L sodium hypophosphite and 70ml/L nickel salt, and the chemical nickel plating solution is an aqueous solution containing 120ml/L sodium hypophosphite and 50ml/L nickel salt. Wherein, the sodium hypophosphite which is used in the alkaline nickel solution is sodium hypophosphite EN-100C, when the sodium hypophosphite EN-100C is consumed by 10ml/L, the sodium hypophosphite EN-100B is used for supplementing into the alkaline nickel solution, so that the content of the sodium hypophosphite in the alkaline nickel solution is always kept to be 120 ml/L. Similarly, the sodium hypophosphite which is used in the chemical nickel plating solution at the beginning is sodium hypophosphite 998B, and after the sodium hypophosphite 998B is consumed by 10ml/L, the sodium hypophosphite 998C is used for being added into the chemical nickel plating solution, so that the content of the sodium hypophosphite in the chemical nickel plating solution is always kept at 120 ml/L.

D, gold plating: soaking the aluminum material into thick gold plating solution at the temperature of 55 ℃ and the current density of 0.2ASD for reaction for 8min, washing with water and drying, wherein the thick gold plating solution is aqueous solution containing 1.5g/L pure gold scutching agent.

E, local shielding: dividing the surface of the aluminum material plated with gold in the step D into a gold plating area and a non-gold plating area according to the requirement, attaching a shielding jig to the surface of the gold plating area to wrap a layer of shielding material, wherein the specific structure of the shielding jig is as follows: the shielding tool includes two patches that correspond the laminating, has the post of inserting on one of them patch, has the jack that supplies to insert the post male on another patch, through laminating two patches respectively on the two sides in gilding district, then utilizes the grafting cooperation of inserting post and jack so that the shielding tool installs on the aluminum product.

F, gold removing: and immersing the partially shielded aluminum material into a gold stripping mixed solution, reacting for 3min, washing with water and drying to obtain the partially gold-plated aluminum material, wherein the gold stripping mixed solution is a mixed solution containing 100ml/L gold stripping solution and 100g/L potassium cyanide.

Example 2

The difference between the local gold plating process on the surface of the aluminum material and the embodiment 1 is that the step A specifically comprises the following steps: putting oil removal powder into an ultrasonic groove, placing the aluminum material into the ultrasonic groove to remove oil for 0.5min, then washing the aluminum material with water, then placing the aluminum material into a nitric acid solution with the volume percentage concentration of 40% to react for 9min, then placing the aluminum material into a sodium hydroxide solution with the concentration of 120g/L to react for 2min at 35 ℃, then washing the aluminum material with water, finally placing the aluminum material into descaling solution to react for 2min, and then washing the aluminum material with water, wherein the descaling solution is the same as the embodiment 1.

Example 3

The difference between the local gold plating process on the surface of the aluminum material and the embodiment 2 is that the step B specifically comprises the following steps: and C, immersing the aluminum material subjected to surface treatment in the step A into a first zinc dipping solution, reacting for 30 seconds, then washing with water, immersing the aluminum material into a zinc removing solution, reacting for 15 seconds, washing with water, immersing the aluminum material into a second zinc dipping solution, reacting for 15 seconds, and washing with water. The first zinc dipping solution and the second zinc dipping solution are mixed solution containing 50% of zinc oxide, 40g/L of sodium hydroxide and 6g/L of potassium cyanide, and the zinc removing solution is nitric acid solution with the volume percentage concentration of 40%.

Example 4

The difference between the local gold plating process on the surface of the aluminum material and the embodiment 3 is that the step C specifically comprises the following steps: and C, putting the aluminum material subjected to zinc dipping in the step B into an alkaline nickel solution for reacting for 6min, washing with water, putting the aluminum material into a chemical nickel plating solution with the pH value of 4.6 for reacting for 35min at 83 ℃, washing with water, putting the aluminum material into an electroplating nickel plating solution with the pH value of 4.4 for reacting for 12min at 50 ℃, and washing with water. The alkaline nickel solution and the electroless nickel plating solution were the same as in example 3, and the electroless nickel plating solution was a mixed solution containing 40g/L of nickel amide, 30g/L of nickel chloride, and 35g/L of boric acid.

Example 5

The difference between the local gold plating process on the surface of the aluminum material and the embodiment 4 is that the step D specifically comprises the following steps: and C, immersing the nickel-plated aluminum material in the step C into a gold pre-plating solution at the temperature of 60 ℃ and the voltage of 2.4V for reaction for 1min, then washing with water, immersing the aluminum material into a thick gold plating solution at the temperature of 55 ℃ and the current density of 0.2ASD for reaction for 8min, washing with water and drying. Wherein the pre-gold plating solution is an aqueous solution containing 0.8g/L of pure gold cylinder opener, and the thick gold plating solution is an aqueous solution containing 1.5g/L of pure gold cylinder opener.

Example 6

The difference between the local gold plating process on the surface of the aluminum material and the embodiment 5 is that after the step F of gold stripping, a protection step is added, and the protection step specifically comprises the following steps: and (3) placing the local gold-plated aluminum material in an aqueous solution of a constantan sheet with the volume percentage concentration of 0.1% at 45 ℃, reacting for 15s, washing with water and drying.

Example 7

The difference between the local gold plating process on the surface of the aluminum material and the embodiment 6 is that the parameters corresponding to all the steps are different, and the specific parameters are shown in table 2.

TABLE 2 summary of parameters for each step of example 7

Comparative example

A local gold plating process for the surface of an aluminum material comprises the following steps.

A, surface treatment:

soaking the aluminum material in 200ml/L of cleaning agent, then washing with water, removing residual stains on the surface of the product by using the cleaning agent, soaking the aluminum material in 200g/L of sodium hydroxide solution for alkali etching, and then washing with water.

B, zinc dipping:

and C, soaking the aluminum material obtained in the step A in a zinc dipping solution at 25 ℃ for 1.5min, and then washing with water, wherein the zinc dipping solution is prepared according to the following concentration: 40g/L zinc sulfate, 35g/L nickel sulfate and 20g/L, DTPMP20 ammonium acetate, 20 g/20 g/L ammonium acetate. And then soaking the aluminum material in a nitric acid solution with the volume percentage concentration of 50% until the zinc coating is removed, and then washing with water. And finally, soaking the aluminum material in a zinc dipping solution at 25 ℃ for 4min, and then washing with water, wherein the zinc dipping solution is prepared from 40g/L of zinc sulfate, 35g/L of nickel sulfate and 20g/L, DTPMP20g/L of ammonium acetate according to the concentration.

C, nickel plating:

and C, immersing the aluminum material obtained in the step B into a nickel plating solution for 15min at 80 ℃, and washing with water, wherein the nickel plating solution is prepared according to the following concentration: 25g/L nickel sulfate, 15g/L citric acid, 25g/L sodium hypophosphite, 15g/L lactic acid, 15g/L succinic acid and 2mg/L thiourea, and finally adjusting the pH value to 4.7 by using ammonia water.

D, palladium plating:

and C, immersing the aluminum material obtained in the step C into a palladium plating solution for 10min at 80 ℃, and washing with water, wherein the palladium plating solution is prepared according to the following concentration: 2g/L of palladium sulfate, 15g/L of citric acid and 3g/L of sodium hypophosphite, and finally adjusting the pH value to 5 by adopting ammonia water.

E, gold plating:

d, immersing the aluminum material obtained in the step D into a gold plating solution for 10min at the temperature of 80 ℃, washing with water, and preparing the gold plating solution for electroless gold plating according to the following concentration: 1g/L of gold sulfite, 15g/L of citric acid and 2g/L of sodium hypophosphite, and finally adjusting the pH value to 5 by adopting ammonia water.

Finished product inspection

(1) Original appearance: according to finished product inspection standards, workers observe the surface of the finished product under a microscope, and the observation surface is qualified without the phenomena of dirt, peeling, bubbling and darkening of luster.

(2) Appearance after high temperature test: and (3) placing the finished product in a high-temperature furnace at the temperature of 400 ℃ for 10 minutes, taking out the finished product, and observing that the surface of the product is qualified without adverse phenomena such as discoloration, bubbling and the like.

(3) Coating binding force: according to the 'test standard of the bonding force of the plating layer' on the hundred grids, a hundred grid knife with the edge width of about 10mm-12mm is used for transversely and longitudinally scribing 10 multiplied by 10 (100) small square grids on the surface of a test sample, and each scribing line is deep to the plated part by taking 1mm as an interval. The sample surface was then gently brushed 5 times backwards and 5 times forwards against the two diagonals of the grid pattern with a pappus brush. Then, the small mesh to be tested is firmly stuck by using a 3M adhesive tape or an adhesive paper with the same effect, and the adhesive tape is strongly wiped by using an eraser to increase the contact area and the contact force between the adhesive tape and the tested area. Finally, one end of the adhesive tape was grasped by hand, the adhesive paper was quickly pulled off in the vertical direction (90 °), and the surface was observed with a magnifying glass. The grade of the detection result is classified into 6 grades which are 0-5 grades respectively, the smaller the number is, the higher the grade is, and the stronger the binding force of the plating layer is.

TABLE 3 test data for examples 1-7 and comparative examples

It can be seen from the data in table 3 combined with example 1 and comparative example that the products processed by the two process steps have greatly different performance in terms of bonding force, and the products processed by the comparative example can only reach grade 3 in the test of coating bonding force, namely, the coating partially or completely falls off in large fragments along the cutting edge, or partially or completely falls off on different parts of the grid, and the affected cross cutting area is obvious. Secondly, after a high-temperature test at 400 ℃, the phenomena of large-area shedding and bubbling and dark color appear, and the bonding force of the plating layer is proved to be poor at high temperature.

It can be seen by combining examples 1 and 2 and the data in table 3 that, a nitric acid pickling step is added before the alkaline etching step, the processed product has excellent original appearance, the level of the plating adhesion is improved from the original level 2 to the level 1 in the test of the plating adhesion, in addition, after the product is placed at 400 ℃ for 10 minutes, the appearance phenomenon is greatly improved, and the shedding degree of the gold plating layer is greatly reduced, so that it can be inferred that a level with higher cleanliness is formed on the surface of the aluminum material in the surface treatment step, which has an obvious positive effect on the plating adhesion, and the nitric acid pickling step is added before the alkaline etching step, so that a relatively dense oxide film on the surface of the aluminum material can be loosened, thereby enhancing the cleaning effect of the post-step on the surface of the aluminum material, and enabling the surface of the aluminum material to achieve higher cleanliness.

When the data of example 2 and example 3 are combined and the data in table 3 are combined, the product processed in example 3 has very few peeling points and foaming phenomena after the high temperature test, and the coating binding force is improved to a certain extent at high temperature compared with the product processed in example 2. It can be inferred that the zinc dipping is carried out only once in the zinc dipping step, the obtained zinc coating is loose, and the good binding force between the plated piece and the electroplated coating can not be ensured.

The detection results of example 3 and example 4 are combined to show that the product prepared in example 4 has improved coating bonding force, and it is presumed that nickel plating is performed after a nickel layer is primarily formed on the surface of the aluminum material, so that a nickel layer can be further formed on the aluminum material, and the bonding force between the nickel layer and the aluminum material can be further enhanced.

The results of the tests of example 4 and example 5 show that the product obtained in example 5 has improved plating adhesion, and the product obtained in example 5 has improved plating adhesion, reduced peeling area and reduced bubbling degree at 400 ℃, so that the product obtained in example 5 has less plating adhesion than the product obtained in the previous step without pre-gold plating step before thick gold plating.

As can be seen from the results of the tests in examples 5 and 6, the gold-plating layer of the product obtained by the process in example 6 has no color change after the high-temperature test, so it can be presumed that after the product is partially gold-plated, a protection step is added to the product to slow down the oxidation of the gold-plating layer, so that the gold-plating layer is not prone to color change.

The detection results of the embodiment 6 and the embodiment 7 show that the original plating bonding force and the plating bonding force after the high temperature test of the products processed in the two embodiments have no big difference on the reverse side, and the process conditions of the steps have no big influence on the bonding force of the gold plating layer of the product within the parameter range, which indicates that the gold plating layer of the product obtained within the parameter range defined in the present application has a good effect.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. A local gold plating process for the surface of an aluminum material is characterized by comprising the following steps: the method comprises the following steps:

2. The process for gold-plating the surface of the aluminum material locally according to claim 1, characterized in that: the specific process of the surface treatment in the step A comprises the following steps: placing the aluminum material in a nitric acid solution for pickling and then washing with water, then placing the aluminum material in an alkali solution for alkali etching and then washing with water, and finally placing the aluminum material in a descaling solution for descaling and then washing with water.

3. The process for gold-plating the surface of the aluminum material locally according to claim 2, characterized in that: the volume percentage concentration of the nitric acid solution is 40-60%, the alkali solution is a sodium hydroxide solution with the concentration of 80-120g/L, the descaling solution is a mixed solution containing a descaling agent, nitric acid, phosphoric acid and an activating salt, wherein the descaling agent accounts for 10-20% of the volume percentage concentration of the descaling solution, the nitric acid accounts for 20-30% of the volume percentage concentration of the descaling solution, the phosphoric acid accounts for 40-60% of the volume percentage concentration of the descaling solution, and the activating salt accounts for 40-200g/L of the descaling solution.

4. The process for gold-plating the surface of the aluminum material locally according to claim 1, characterized in that: the zinc dipping process in the step B comprises the following specific steps: and C, immersing the aluminum material subjected to surface treatment in the step A into a first zinc dipping solution for reaction, then washing with water, immersing the aluminum material into a zinc removing solution for reaction, then washing with water, and finally immersing the aluminum material into a second zinc dipping solution for reaction, and then washing with water.

5. The process for gold-plating the surface of the aluminum material locally according to claim 4, characterized in that: the first zinc dipping solution and the second zinc dipping solution are mixed solution containing 30-50% of zinc precipitating tank opening agent, 20-40g/L of sodium hydroxide and 2-6g/L of potassium cyanide; the dezincification solution is a nitric acid solution with the volume concentration of 40-60%.

6. The process for gold-plating the surface of the aluminum material locally according to claim 4, characterized in that: the reaction time of the first zinc dipping is 30-50s, the reaction time of the zinc stripping is 15-30s, and the reaction time of the second zinc dipping is 15-20 s.

7. The process for gold-plating the surface of the aluminum material locally according to claim 1, characterized in that: the specific process of nickel plating in the step C comprises the following steps: and C, putting the aluminum material subjected to zinc dipping in the step B into an alkaline nickel solution for reaction, washing with water, putting the aluminum material into a chemical nickel plating solution with the pH of 4.6-5 for reaction, washing with water, and finally putting the aluminum material into the electrolytic nickel plating solution for reaction and washing with water.

8. The process for gold-plating the surface of the aluminum material locally according to claim 7, wherein: the alkaline nickel solution is mainly an aqueous solution containing 120ml/L sodium hypophosphite and 70ml/L nickel salt; the chemical nickel plating solution is mainly an aqueous solution containing 120ml/L sodium hypophosphite and 50ml/L nickel salt; the nickel electroplating solution is a mixed solution containing 40-70g/L of nickel amide, 30-50g/L of nickel chloride and 35-45g/L of boric acid.

9. The process for partially plating gold on the surface of an aluminum material according to any one of claims 1 to 8, wherein: the specific process for gold plating in the step D comprises the following steps: and C, immersing the aluminum material plated with nickel in the step C into a gold pre-plating solution at 45-60 ℃ for electroplating for 1-2min, then washing with water, immersing the aluminum material into a thick gold plating solution at 55-60 ℃ for electroplating for 6-8min, washing with water and drying.

10. The process for gold-plating the surface of the aluminum material partially according to claim 9, wherein: the pre-gold plating solution is an aqueous solution containing 0.8-2g/L of pure gold cylinder opening agent; the thick gold plating solution is an aqueous solution containing 1.5-2.5g/L of pure gold cylinder opener.