CN100415942C - Preparation method of nanocrystalline zinc coating - Google Patents

Abstract

The invention relates to a preparation method of a pulse electrodeposited nanocrystalline zinc coating, which belongs to the technical field of pulse electroplating technology. The preparation process and steps of the method of the present invention are: (1) first preparing an acidic zinc sulfate plating solution with a concentration of 300 to 700 g/L, and adjusting the pH value to 1 to 4 with dilute sulfuric acid; (2) adding thiourea Mixed organic additives with benzylidene acetone, the concentration of thiourea is 0.5-3g/L, the concentration of benzylidene acetone is 0.1-2g/L; the temperature of the plating solution is 15-50°C; (3) It is carried out by pulse electroplating method Pulse electrodeposition: In the electroplating tank filled with the above-mentioned zinc sulfate solution, the steel plate to be plated is used as the cathode, and the insoluble electrode is used as the anode, and a pulse current is applied. The peak value of the pulse current density is 0.1-5A/cm ² , and the total plating time 1 to 15 minutes; finally, a nanocrystalline zinc coating with a particle size of less than 100 nm can be obtained.

Description

Preparation method of nanocrystalline zinc coating

technical field

The invention relates to a preparation method of a pulse electrodeposited nanocrystalline zinc coating, which belongs to the technical field of pulse electroplating technology.

Background technique

Galvanizing is one of the effective methods for corrosion protection of steel materials. Galvanized steel is widely used in the fields of automobiles, construction, home appliances, chemicals, transportation and national defense. In recent years, with the rapid development of the national economy and the continuous improvement of people's living standards, the demand for galvanized steel in various industrial sectors is increasing, especially the demand for galvanized steel is increasing faster. After the zinc coating is nano-sized, its mechanical, physical, electrical, chemical and other properties are significantly improved, which makes nanotechnology gain rapid development and widespread attention in recent years. Compared with product coatings, nanocrystalline coatings have higher hardness, wear resistance, ductility, corrosion resistance and processability. Therefore, the nanometerization of the galvanized layer is one of the effective technical approaches to improve its comprehensive performance.

Youssef et al. (Influence of additives and pulse electrodeposition parameters onproduction of nanocrystalline zinc from zinc chloride electrolytes, K.M.S.Youssef, et al. Journal of the Electrochemical Society, .2004, Vol.151-C 103-2C The mixed additives of thiourea and polyacrylamide were added to prepare a zinc coating with a grain size of 50nm. People such as Yu Jingxian (research on the structure of nano-bright galvanized layer, Yu Jingxian, etc., Chemical Journal of Chinese Universities, 1999.20 (1): 107-110) also prepared nano-zinc-coated layer by adjusting additives in potassium chloride bright galvanized bath. These studies demonstrate that organic additives can effectively increase the overpotential and nucleation rate of cathodic deposition of zinc, leading to the formation of nanocrystalline zinc layers.

H.Yan et al. (A model for nanolaminated growth patterns in Zn and Zn-CoElectrodeposits, H..Yan, etc. Journal of the Electrochemical Society,, 1996, Vol.143(5): 1577-1583) and Chinese patent ( Application No. 200310107939.X) reported the use of direct current electrodeposition technology to prepare nano-chip laminated zinc coatings in sulfate solution, but the grain size of these coatings has not been nanoscaled on a three-dimensional scale.

Saber et al. (Pulse current electrodeposition of nanocrystalline zinc. Kh. Saber et al., Materials. Science and Engineering. A. 2003, 341: 174-181) used pulse electrodeposition technology to obtain nanocrystalline zinc coatings in chloride baths. Compared with direct current, the pulse electrodeposition method can adopt higher pulse peak current density to increase the overpotential and nucleation rate of zinc cathodic deposition, thereby generating nanocrystalline zinc coating.

At present, it is still difficult to prepare zinc coatings with a grain size of less than 100 nanometers in an acidic sulfate system.

Contents of the invention

The purpose of the present invention is to provide a method for preparing nanocrystalline zinc coating, and adopt suitable process parameters to enable the preparation of zinc coating with grain size less than 100nm.

The invention provides a kind of preparation method of nanocrystalline zinc coating, it is characterized in that having following preparation process and steps:

a. First prepare the acidic zinc sulfate plating solution, the concentration of the zinc sulfate plating solution is 300-700g/L; and adjust with dilute sulfuric acid to make its pH value 1-4;

b. Then add a mixed organic additive, that is, add a mixed additive of thiourea and benzylidene acetone, the concentration of thiourea is 0.5 ~ 3g/L, the concentration of benzylidene acetone is 0.1 ~ 2g/L; the temperature of the plating solution is 15 ~ 50°C;

c. adopt the pulse electroplating method to carry out pulse electrodeposition; in the electroplating tank that fills above-mentioned zinc sulfate solution, take the plated carbon steel as the cathode, take the insoluble electrode as the anode, pass into the pulse current; the pulse current density peak value (Jp) is 0.1～5A/cm ² , the power-on time range (T _on ) is 1-8ms, the power-off time range (T _off ) is 4-15ms, and the total plating time is 1-15 minutes; finally, nanometer particles with a particle size of less than 100nm can be obtained Crystal zinc coating.

The characteristics of the present invention are: (1) the acidic sulfate system is adopted without adding other conductive salts, and the plating solution is easy to maintain; (2) the synergistic effect of the mixed organic additives of thiourea and benzylidene acetone can be used to effectively increase the zinc concentration. The overpotential and nucleation rate of cathodic deposition make it easy to generate nanocrystalline zinc coating; (3) The parameter range of the pulse current signal is wide, and the fluctuation of the signal during the preparation process has little influence on the coating.

Detailed ways

Embodiments of the present invention are described below.

Example 1

The preparation process and steps in this embodiment are as follows:

a. First prepare acidic zinc sulfate plating solution, adopt zinc sulfate (ZnSO _{7H 2} O) to be dissolved in distilled water, be mixed with the zinc sulfate plating solution that concentration is 350g/L, adjust to pH value 1 with dilute sulfuric acid again;

b. Then add a mixed organic additive composed of thiourea (H ₂ NCSNH ₂ ) and benzylidene acetone (C ₆ H ₅ CH=CHCOCH ₃ ); the concentration of thiourea is 1 g/L, and the concentration of benzylidene acetone is 0.5 g/L L; the temperature of the bath is 25°C;

c. Adopt the pulse electroplating method to carry out pulse electrodeposition; In the electroplating tank that fills above-mentioned zinc sulfate solution, take the plated carbon steel as cathode, take Ti/IrO ₂ coating electrode as anode, lead into pulse current; Pulse current density The peak value (Jp) is 2A/cm ² , the power-on time (T _on ) is 4ms, the power-off time (T _off ) is 8ms, and the total plating time is 5min; finally, a nanocrystalline zinc coating with an average particle size of 70nm can be obtained.

The zinc coating obtained in the experiment was tested with an X-ray diffraction analyzer field emission electron microscope, and it was found that the zinc grain size in the nanocrystalline zinc coating was in the range of 57-79nm.

Claims (1)

1. a preparation method of nanocrystalline zinc coating, is characterized in that having following preparation process and step: a. First prepare the acidic zinc sulfate plating solution, the concentration of the zinc sulfate plating solution is 300-700g/L; and adjust with dilute sulfuric acid to make its pH value 1-4; b. Then add a mixed organic additive, that is, add a mixed additive of thiourea and benzylidene acetone, the concentration of thiourea is 0.5 ~ 3g/L, the concentration of benzylidene acetone is 0.1 ~ 2g/L; the temperature of the plating solution is 15 ~ 50°C; c. adopt the pulse electroplating method to carry out pulse electrodeposition; in the electroplating tank that fills above-mentioned zinc sulfate solution, take the plated carbon steel as the cathode, take the insoluble electrode as the anode, pass into the pulse current; the pulse current density peak value (Jp) is 0.1～5A/cm ² , the power-on time range (T _on ) is 1-8ms, the power-off time range (T _off ) is 4-15ms, and the total plating time is 1-15 minutes; finally, nanometer particles with a particle size of less than 100nm can be obtained Crystal zinc coating.