CN102127793A - Composite electroplating method of chrome-nano silicon dioxide of steel - Google Patents

Abstract

The invention relates to a chromium-nano-silicon dioxide composite electroplating method for steel. The main method is to prepare nano-silicon dioxide into nano-powder and add it to the chromium-plating solution. The chromium-plating solution of the present invention is stable and has strong dispersion ability; the cathodic current efficiency increase; the microhardness of the chrome-plated layer after electroplating increases; the corrosion current density and surface carrier density of the chrome-plated layer are far lower than those of the chrome-plated layer without adding nano-silica through the Tafel curve test and Mott-Schottky analysis, indicating that the composite electroplating The final coating has better corrosion resistance.

Description

Chromium-nanometer silicon dioxide composite electroplating method for steel

technical field

The invention relates to a method for chromium-silicon dioxide composite electroplating of metal or steel, and belongs to the technical field of metal surface electroplating technology.

Background technique

Electroplating has been widely used in anti-corrosion, anti-corrosion, wear-resistant, surface decoration and other workpieces, and has developed into common electroplating, alloy electroplating, composite electroplating, plastic electroplating, precious metal electroplating, brush plating and other types. Chromium plating is one of the most widely used plating types in the electroplating process. The chromium layer has excellent performance, strong passivation ability, good chemical stability, high hardness and reflection ability, and low friction coefficient. It is widely used in protective decoration. And in the wear-resistant coating, and chromium is relatively easy to deposit from the aqueous solution, the process is relatively simple and easy to control.

There are still many problems in electroplating chromium in actual large-scale industrial production, mainly: (1) chromic acid has high toxicity, which is very harmful to human health, and waste gas and waste acid must be treated, so it costs more; (2) ) Due to the low current efficiency and high cell voltage, the power consumption is large; (3) Due to the use of high current density, the investment in power equipment increases; (4) Due to the use of insoluble anodes, the consumed metal chromium needs to be frequently supplemented with chromium Only acid can keep the relative stability of the components in the electroplating solution; (5) Due to the large amount of hydrogen evolution at the cathode, hydrogen embrittlement occurs in the chromium plating layer and the base metal.

Although some electroplating factories have overcome one of the above major problems, such as the brightness of the coating, the corrosion resistance requirements have not been met. Some use trivalent chromium instead of hexavalent chromium to reduce environmental pollution. , but the bond strength or coating thickness is not completely resolved. At present, people are looking for a chrome substitute or researching a new chrome plating process. The development of nanotechnology provides new opportunities for upgrading the technical content of traditional industries.

Nanoparticles have special effects such as surface effect, small size effect, quantum size effect, and macroscopic quantum tunneling effect. It can be used to improve the optical, magnetic, electrical, mechanical and other properties of materials or to give them new functions, which can greatly improve the product quality in the application field, and has good theoretical research value and application prospects. In addition, with the advancement of technology, the preparation cost of nanopowder and film layer has also been greatly reduced, laying a solid material foundation for the large-scale application of nanotechnology.

Nano-surface technology is developing rapidly, among which nano-composite electroplating technology is more researched and applied. Composite coating is a special coating formed by uniformly mixing one or more insoluble solid particles and fibers into the metal coating by metal electrodeposition or co-deposition. The composite coating formed with superhard material as dispersed particles and metal is called superhard material composite coating. Nanocomposite coatings have become one of the hotspots in the field of nanosurface engineering research. Scientists from the former Soviet Union added nano-diamonds to the chromium plating solution, which significantly improved the hardness and wear resistance of the chromium plating layer. This technology has obtained a patent and is widely used in the CIS countries. my country has also carried out related work, such as patent No. 200610117075.3 Composite chemical deposition method of nano-ceramic materials and metal alloys on metal surfaces, patent number 200310107939.X Electroplating preparation method of nano-multilayer zinc film.

Contents of the invention

The purpose of the present invention is to provide a method for electroplating a chromium-silicon dioxide composite coating on the surface of metal or steel.

The present invention is a chromium-silicon dioxide composite electroplating method for steel, which is characterized in that it has the following processes and steps:

a. Prepare a composite electroplating solution, that is, a composite electroplating solution containing cadmium and nano silicon dioxide;

First prepare the nano-silica aqueous dispersion: grind the high-purity silica powder through grinding-dissolving-grinding-drying, and repeat the previous steps three times; then put the air-dried powder into a ball mill and ball-mill it into nano-powder, After ultrasonic activation treatment, the nano-silica water dispersion is obtained; in the process of water dissolution, deionized water is used for powder dissolution; the drying temperature is 80~95°C; the speed of the ball mill is 100~350r/min; the ball milling time is 8-15 hours ; The ratio of raw material to zirconium beads is 1: (10~18); ultrasonic activation is at 2A level ultrasonic intensity;

Prepare chromium-silicon dioxide composite electroplating solution, its composition and consumption are:

Chromic anhydride 240~260g/L

Sulfuric acid 2.4~2.6g/L

Nano silica 1~5g/L

b. Place the metal or steel to be plated in the electroplating tank filled with the above-mentioned composite electroplating solution, and use the metal or steel plated workpiece as the cathode, and the lead-antimony alloy as the anode, and simultaneously connect the negative pole and the positive pole of the DC power supply Connected by wires; the process parameters used in electroplating are as follows:

Temperature 45~55℃

Current density 45~60A/ ^dm2

Stirring solution circulation 80~120r/min

Cathode and anode area ratio 1.0~2.5

Finally, a chromium-nanometer silicon dioxide composite coating is obtained on the steel surface.

Advantages of the inventive method

Compared with the high-concentration chromium plating process of the prior art, the present invention has the following advantages:

1) Nano silica powder is easy to prepare, stable in performance and resistant to strong acid;

2) The nano silicon dioxide of the present invention is easy to add, and the qualification rate of the coating after electroplating is above 95%; and the cathode current efficiency is high, saving energy.

3) The dispersion ability of the plating solution is good, and it can electroplate complex parts. The coating has high hardness, excellent wear resistance and corrosion resistance.

The plating solution of the method of the invention cannot contain fluoride and other additives with corrosive components, otherwise the anode will produce a large amount of lead chromate particles, which will affect the mechanical properties of the coating. The solution is circulated and stirred by a magnetic pump.

Detailed ways

Specific embodiments of the present invention are described below.

Example

1, in the present embodiment, at first prepare nano silicon dioxide powder, its process is as follows:

Grinding—dissolving—grinding—oven drying into powder—repeating the previous steps 3 times—putting the powder into a ball mill and ball milling into nano powder—ultrasonic activation treatment.

Among them, deionized water is used for powder dissolution; oven temperature is 80°C; ball mill speed is 300r/min, ball milling time is 12 hours, large zirconium beads: small zirconium beads: ball milling raw materials = 120g: 240g: 20g, ultrasonic activation treatment is at 2A level Ultrasonic activation treatment is performed on the nano-silica water dispersion system under the intensity.

2. Configuration of chrome plating solution and setting of chrome plating process parameters

Chromic anhydride 250g

Sulfuric acid 2.5g

Prepare the plating solution with deionized water, the volume of deionized water is 1L; the plating solution is divided into 3 parts, the first chromium plating solution does not add nano-silica, the second chrome plating solution adds nano-silica 2g, and the third chromium plating solution Add nano silicon dioxide 4g to the solution.

Temperature 50℃

Current density 50A/ ^dm2

Stirring solution circulation 100r/min

Cathode to anode area ratio 2

The electroplating base material is H13 steel. After electroplating, the sample is tested for microhardness, cathodic current efficiency, corrosion current density and carrier density. The obtained performance test values are shown in the following table:

Performance

It can be seen from the above table that with the increase of the addition of silicon dioxide, the microhardness of the chromium plating layer and the cathode current efficiency gradually increase; the corrosion current density and carrier density decrease, and the corrosion resistance increases.

The method for electrochemical testing of electroplated coatings is as follows:

The electrochemical test was carried out on the chrome-plated layer. The electrochemical experiment used a three-electrode system, the reference electrode was a saturated calomel electrode, and the auxiliary electrode was a platinum sheet. Analytical grade reagents were used as test drugs, and solutions were prepared with deionized water. After drying, the electrode is soaked in 5% Na ₂ SO ₄ solution at room temperature (the electrode working surface is not in contact with the auxiliary electrode or reference electrode); then the potential-time, impedance-potential and polarization curves are measured. The measurement of the electrode system adopts CHI660 electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.) controlled by PC computer. The measurement frequency is 1000Hz, and then Mott-Schotty analysis is performed on the impedance-potential data to calculate the surface carrier density of the electrode, and the polarization curve is analyzed to calculate the corrosion current density.

Claims (1)

1. the chromium of steel-silicon-dioxide composite plating method is characterized in that having following process and step:

A. prepare composite plating solution, promptly contain the composite plating solution of cadmium and nano silicon;

At first prepare the nano silicon aqueous dispersion: highly purified SiO 2 powder through grinding-dissolving-grinding-oven dry, and is repeated preceding step three times; Then air-dry powder is put into the ball mill ball milling and become nano-powder, handle through ultrasonic activation more at last, obtain the nano silicon aqueous dispersion; In the water-soluble process, the powder dissolution deionized water; Bake out temperature is 80 ~ 95 ℃; Drum's speed of rotation 100 ~ 350r/min; The ball milling time is 8-15 hour; Raw material is 1:(10 ~ 18 with the ratio of zirconium pearl); Ultrasonic activation is at 2A level ultrasound intensity;

Preparation chromium-silicon-dioxide composite plating solution, its composition and consumption thereof are:

Chromic anhydride 240 ~ 260g/L

Sulfuric acid 2.4 ~ 2.6g/L

Nano silicon 1 ~ 5g/L

B. will desire metal or steel that plating handles and be positioned in the plating tank that fills above-mentioned composite plating solution, and with metal or steel electroplating parts as negative electrode, be anode with the lead antimony alloy, negative pole and the positive pole respectively at direct supply is connected by lead simultaneously; It is as follows to electroplate the processing parameter that adopts:

45 ~ 55 ℃ of temperature

Current density 45 ~ 60A/dm ²

Stirred solution circulation 80 ~ 120r/min

The negative electrode annode area is than 1.0 ~ 2.5

Finally obtain chromium-nano silicon composite deposite at steel surface.