CN112323109A - Cyanide-free plating solution for low-tin alloy and preparation method thereof - Google Patents

Abstract

The invention relates to the field of metal material surface treatment, in particular to a cyanide-free plating solution for low-tin alloy and a preparation method thereof, wherein the cyanide-free plating solution comprises copper sulfate, tin salt LD5130M, additive LD5130RS, the content of copper sulfate is 24-36 g/L, the content of tin salt LD5130M (Chongqing Li Daiz Co., Ltd.) is 350-450 ml/L, the content of additive LD5130RS (Chongqing Li Daiz Co., Ltd.) is 200-300 ml/L, and the pH value of the cyanide-free plating solution is 10.5-11 A stable low tin alloy coating that is corrosion resistant.

Description

Cyanide-free plating solution for low-tin alloy and preparation method thereof

Technical Field

The invention relates to the field of surface treatment of metal materials, in particular to a cyanide-free plating solution for low-tin alloy and a preparation method thereof.

Background

The electroplated copper-tin alloy (copper-tin alloy plating), also called bronze plating, is the most widely used alloy plating in China and the largest production scale. The electroplated copper-tin alloy can be divided into a high-tin alloy, a medium-tin alloy and a low-tin alloy according to the tin content in the alloy.

The high tin alloy has a tin content of more than 40%, is also called white bronze, has hardness between nickel and chromium, and has mirror luster after polishing. The plating has good stability in air and good milling and welding capacity and conductive capacity, but the plating is too brittle to withstand deformation.

The medium tin alloy has a tin content of 15-30%, has better hardness and oxidation resistance than the low tin alloy, can be used as a bottom layer of a decorative coating, but is not suitable for a surface coating.

The low-tin alloy has a tin content of less than 15%, is cathodic protection for steel, has good protective capacity, has good wear resistance and certain lubricity, and can meet the performance requirements of high wear resistance, ablation resistance and corrosion resistance of parts of certain military products at present.

The current process for electroplating copper-tin alloy in industrial application mainly adopts three kinds of plating solutions, namely cyanide plating solution, low-cyanide plating solution and cyanide-free plating solution. Among them, the process using cyanide plating solution is a well-established method, and has been widely used for electroplating low-tin alloys, medium-tin alloys, and high-tin alloys.

The main components of the commonly used cyanide plating solution comprise NaCN (free sodium cyanide, the content of which is 4-20 g/L, CuCN (cuprous cyanide, the content of which is 20-40 g/L), NaOH (sodium hydroxide, the content of which is 7-10 g/L), sodium stannate Na₂SnO₃The content is 30-40 g/L), and the balance is water. In the plating solution system, an alloy plating layer with any composition can be obtained by changing different main salt concentration ratios and process conditions, and the plating solution has the characteristics of stable solution, simple maintenance, strong solution dispersing capacity and the like, and has the main defects that NaCN (sodium cyanide) and CuCN (cuprous cyanide) are used in the formula of the plating solution, so that CN- (cyanide) exists in the solution, and cyanide is a highly toxic substance,therefore, the solution has high toxicity, is not beneficial to safe production and environmental protection, and is rejected by the compulsory laggard process listed by the nation.

Only the low cyanide plating solution prepared by pyrophosphate, triethanolamine and the like is suitable for electroplating low tin alloy, but the low cyanide plating solution is unstable and has weak dispersing ability, so that the low cyanide plating solution cannot be applied on a large scale.

Although the cyanide-free plating high-tin alloy process adopting the cyanide-free plating solution has certain application in the friction and automobile parts, the cyanide-free plating solution adopted by the cyanide-free plating high-tin alloy process cannot be applied to electroplating of low-tin alloys, and the problem to be solved is urgently needed to research the cyanide-free plating solution suitable for electroplating of the low-tin alloys so as to meet the performance requirements of high abrasion resistance, ablation resistance and corrosion resistance of parts of certain military products at present.

Disclosure of Invention

The invention aims to provide a cyanide-free plating solution for low-tin alloy and a preparation method thereof, aiming at the corresponding defects of the prior art, cyanide-free complex compounds are adopted to replace cyanide complex compounds to complex copper ions, tin ions and the like in the plating solution, so that the cyanide-free plating solution with good stable dispersibility and no toxicity is obtained, an additive LD5130RS (Chongqing Lidao science and technology Co., Ltd.) is utilized to enable the electroplating process to be more stable, and the cyanide-free plating solution is adopted to electroplate a plated part, so that a bright, fine, wear-resistant and corrosion-resistant stable low-tin alloy plating layer can be formed on the surface of the plated part.

The purpose of the invention is realized by adopting the following scheme: the cyanide-free plating solution for the low-tin alloy comprises copper sulfate, tin salt LD5130M and an additive LD5130RS, wherein the content of the copper sulfate is 24-36 g/L, the content of the tin salt LD5130M is 350-450 ml/L, and the content of the additive LD5130RS is 200-300 ml/L; the pH value of the cyanide-free plating solution is 10.5-11.

The better technical proposal is that the content of the copper sulfate is 24g/L, the content of the tin salt LD5130M is 360ml/L, and the content of the additive LD5130RS is 240 ml/L.

The better technical proposal is that the content of the copper sulfate is 30g/L, the content of the tin salt LD5130M is 420ml/L, and the content of the additive LD5130RS is 280 ml/L.

The better technical proposal is that the content of the copper sulfate is 36g/L, the content of the tin salt LD5130M is 450ml/L, and the content of the additive LD5130RS is 300 ml/L.

The preparation method of the cyanide-free plating solution for the low-tin alloy comprises the following steps:

1) taking the components of the cyanide-free plating solution according to the proportion of any one of the technical schemes;

2) adding deionized water into the electroplating bath, wherein the volume of the deionized water is one third of that of the plating solution to be prepared, then sequentially and slowly adding tin salt LD5130M (Chongqing Lidao science and technology Co., Ltd.) and additive LD5130RS (Chongqing Lidao science and technology Co., Ltd.) and uniformly stirring;

3) dissolving copper sulfate with a small amount of deionized water, slowly adding into the electroplating bath, and uniformly stirring;

4) adding deionized water into the electroplating bath until the volume of the plating bath is one liter;

5) stirring uniformly, adjusting the pH value of the solution to 10.5-11, and standing for 24 hours.

The method for adjusting the pH value in the step 5) is to add a dilute sulfuric acid solution or a sodium hydroxide solution.

The invention has the advantages that cyanide-free complex is adopted to replace cyanide complex to complex copper, tin and other ions in the plating solution, so as to obtain stable cyanide-free plating solution with good dispersibility and no toxicity, an additive LD5130RS (Chongqing Ridgeon science and technology Co., Ltd.) is utilized to make the electroplating process more stable, and the cyanide-free plating solution is adopted to electroplate the plated piece, so that a bright, fine, wear-resistant and corrosion-resistant stable low-tin alloy plating layer can be formed on the surface of the plated piece.

Detailed Description

Example 1

Preparing one liter of cyanide-free plating solution for low-tin alloy, wherein the content of each component is as follows: the copper sulfate content is 24g/L, the tin salt LD5130M content is 360ml/L, the additive LD5130RS content is 240ml/L, and the balance is deionized water.

Example 2

Preparing one liter of cyanide-free plating solution for low-tin alloy, wherein the content of each component is as follows: the copper sulfate content is 30g/L, the tin salt LD5130M content is 420ml/L, and the additive LD5130RS content is 280 ml/L.

Example 3

Preparing one liter of cyanide-free plating solution for low-tin alloy, wherein the content of each component is as follows: the copper sulfate content is 36g/L, the tin salt LD5130M content is 450ml/L, and the additive LD5130RS content is 300 ml/L.

The cyanide-free plating solutions for low-tin alloys described in examples 1 to 3 were prepared as follows:

1) taking the components of the cyanide-free plating solution according to the proportion;

2) adding deionized water into the electroplating bath, wherein the volume of the deionized water is one third of that of the plating bath to be prepared, and then sequentially and slowly adding tin salt LD5130M and additive LD5130RS and uniformly stirring;

3) dissolving copper sulfate with a small amount of deionized water, slowly adding into the electroplating bath, and uniformly stirring;

4) adding deionized water into the electroplating bath until the volume of the solution in the electroplating bath is equal to that of the plating solution to be prepared;

5) stirring the solution in the electroplating bath uniformly, adjusting the pH value to 10.5-11 by using a dilute sulfuric acid solution or a sodium hydroxide solution, and standing for 24 hours.

The electroplating method of the cyanide-free plating solution comprises the following steps of taking enough cyanide-free plating solution with the proportion of example 1, 2 or 3 to electroplate a plated part:

firstly, take the plated part (the plated part is a left buffer or a right buffer, etc.)

Checking the appearance of the plated part, taking the plated part without rust, oxide skin, welding slag, welding air holes, cracks, bruises and burrs, or else, not electroplating;

chemical degreasing

Mixing a sodium hydroxide solution with the concentration of 60-80 g/L, a sodium carbonate solution with the concentration of 50-100 g/L and a trisodium phosphate solution with the concentration of 10-15 g/L in a chemical degreasing tank, heating to 80-100 ℃, putting into a plated part, and soaking for 2-20 min, wherein the soaking time can be properly prolonged when oil stains are serious;

washing the ground product

Cleaning the plated part in a rinsing bath for 0.5-2 min by using normal-temperature tap water;

fourth electrochemical degreasing

Mixing a sodium hydroxide solution with a concentration of 60-80 g/L, a sodium carbonate solution with a concentration of 50-100 g/L and a trisodium phosphate solution with a concentration of 10-15 g/L in an electrochemical degreasing bath, heating to 80-100 ℃, and electrochemically degreasing the plated part for 1-3 min by using a current with a current density of 2-5A/dm;

fifthly, washing with hot water

Cleaning the plated part in a hot water tank for 0.5-2 min by using tap water at the temperature of 70-100 ℃;

sixthly, cleaning

Cleaning the plated part in a rinsing bath for 0.5-2 min by using normal-temperature tap water;

weak etching treatment

Adding hydrochloric acid with the concentration of 80-120 g/L and tincture with the concentration of 1g/L into a weak etching groove, and then putting a plating piece into the weak etching groove for soaking for 0.5-10 min;

and cleaning

Cleaning the plated part in a rinsing bath for 0.5-2 min by using normal-temperature tap water;

copper plating of the self-body

Adjusting the pH value of an LD-5100M solution (Chongqing Liaoshijiu Co., Ltd.) with the concentration of 400-600 ml/L to 9-10 by adding a dilute sulfuric acid solution or a sodium hydroxide solution, placing the LD-5100M solution in a copper plating tank, heating to 40-55 ℃, uniformly stirring (air or mechanical stirring), immersing a plated part, introducing a current with the current density of 1-3A/dm, plating copper for 5-10 min,

is superior to cleaning

Cleaning the plated part in a rinsing bath for 0.5-2 min by using normal-temperature tap water;

electroplating of

Filling the cyanide-free plating solution for the low-tin alloy in the embodiment 1, 2 or 3 in a plating tank, heating to 35-40 ℃, uniformly stirring (air or mechanical stirring), immersing the plated piece into the cyanide-free plating solution, introducing a current with a current density of 0.2-3A/dm to electroplate the plated piece, and electroplating for 5-6 h;

water pumping cleaning

Cleaning the plated part in a rinsing bath for 0.5-2 min by using normal-temperature tap water;

passivation of the selection

Heating a potassium dichromate solution with the concentration of 50g/L in a passivation tank to 70-85 ℃, and immersing the plated part into the potassium dichromate solution for passivation for 8-10 min;

self-absorption three-stage counter-current rinsing

Carrying out three-stage countercurrent rinsing on the plated part for 0.5-2 min in a rinsing bath by adopting normal-temperature tap water;

the plated part is naturally aired.

After electroplating the plated part by the technical scheme, the corrosion resistance test of the plated part by adopting a neutral salt spray test can be known:

the method not only avoids the problem of huge toxicity of the cyanogen-containing plating solution adopted by the cyanogen-containing electroplating process, is beneficial to safe production and environmental protection, but also can achieve the electroplating effect of the cyanogen-containing electroplating process, and the plated part can be corroded in a neutral salt spray environment for more than 144 hours.

The wear resistance of the plating layer of the plated part is detected according to the method in the standard GB/T1768-2006 "method for measuring the wear resistance of colored paint and varnish by rotating rubber grinding wheel method":

the mass loss of the plated piece obtained by adopting the cyanogen-containing electroplating process is 549mg, while the mass loss of the plated piece obtained by adopting the electroplating solution prepared by the invention to carry out the electroplating process is 474mg, so that the wear resistance is obviously enhanced.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and those skilled in the art can make modifications without departing from the spirit of the present invention.

Claims (6)

1. A cyanide-free plating solution for low-tin alloy is characterized in that: the cyanide-free plating solution comprises copper sulfate, tin salt LD5130M and an additive LD5130RS, wherein the content of the copper sulfate is 24-36 g/L, the content of the tin salt LD5130M is 350-450 ml/L, and the content of the additive LD5130RS is 200-300 ml/L; the pH value of the cyanide-free plating solution is 10.5-11.

2. The cyanide-free plating solution of claim 1, wherein: the copper sulfate content is 24g/L, the tin salt LD5130M content is 360ml/L, and the additive LD5130RS content is 240 ml/L.

3. The cyanide-free plating solution of claim 1, wherein: the copper sulfate content is 30g/L, the tin salt LD5130M content is 420ml/L, and the additive LD5130RS content is 280 ml/L.

4. The cyanide-free plating solution of claim 1, wherein: the copper sulfate content is 36g/L, the tin salt LD5130M content is 450ml/L, and the additive LD5130RS content is 300 ml/L.

5. The method for preparing a cyanide-free plating solution according to claim 1, comprising the steps of:

1) taking the components of the cyanide-free plating solution according to the proportion of any one of claims 1 to 3;

2) adding deionized water into the electroplating bath, wherein the volume of the deionized water is one third of that of the plating bath to be prepared, and then sequentially and slowly adding tin salt LD5130M and additive LD5130RS and uniformly stirring;

3) dissolving copper sulfate with a small amount of deionized water, slowly adding into the electroplating bath, and uniformly stirring;

4) adding deionized water into the electroplating bath until the volume of the plating bath is one liter;

5) stirring uniformly, adjusting the pH value of the solution to 10.5-11, and standing for 24 hours.

6. The method of claim 5, wherein: the method for adjusting the pH value in the step 5) is to add a dilute sulfuric acid solution or a sodium hydroxide solution.