Preparation method of electroplating liquid for small-aperture parts

Abstract

The invention discloses a preparation method of an electroplating solution for small-aperture parts, which comprises the following steps: blending zinc oxide into paste with water, adding the paste into a sodium hydroxide aqueous solution while stirring, cooling to below 35 DEG C, adding zinc powder, stirring, standing and filtering to obtain a mixed solution; and under the stirring state, a 223A alkaline cyanide-free zinc softening agent, a 223B alkaline cyanide-free zinc brightening agent and a 221C alkaline cyanide-free zinc purifying agent are sequentially added into the mixed solution, and the galvanization electroplating solution is obtained. The preparation method of the electroplating liquid is simple; the electroplating solution has good tolerance to metal impurities, the bath solution is stable, and the maintenance method is simple; the use temperature range and the current density of the electroplating liquid are wide; and the dispersing capacity and the depth capacity of the electroplating liquid are relatively good.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a plating solution for small-aperture parts, and belongs to the technical field of workpiece surface treatment. BACKGROUND

[0002] Galvanizing is one of the most economical process methods for preventing corrosion of metal materials, and is widely used in many fields such as light industry, electromechanics, automobiles, national defense and military industry. A traditional galvanizing process adopts DE as an additive to prepare a plating solution, which can meet the galvanizing production of simple-structure parts. With the diversification of part structures, the traditional plating solution for galvanizing cannot meet the galvanizing production of small-aperture parts, the inside of the part holes is usually not plated with a zinc layer, and the thickness difference of the plating layer between the inner and outer surfaces of a tubular part is large, which reduces the corrosion resistance of the part. In addition, DE additive is a reaction product of dimethylamine and epichlorohydrin, and there is a serious environmental problem in the synthesis process. Influenced by the national environmental protection policy, the raw materials and synthetic chemicals of DE additive are strictly limited. Therefore, it is necessary and urgent to invent a green and environmentally-friendly plating solution for galvanizing. SUMMARY

[0003] The application aims to solve the problem that the traditional galvanizing process cannot meet the galvanizing production of small-aperture parts, and provides a preparation method of a plating solution for small-aperture parts.

[0004] The application is achieved by the following technical scheme.

[0005] The application is achieved by the following technical scheme.

[0006] 1) First, sodium hydroxide is poured into water, and stirring is continuously performed to obtain a sodium hydroxide aqueous solution;

[0007] 2) Zinc oxide is adjusted into a paste with water, and the paste is added into the sodium hydroxide aqueous solution under stirring to obtain a mixed solution 1;

[0008] 3) After the mixed solution 1 is cooled to below 35 DEG C, zinc powder is added, air stirring is performed for 30-40 min, and then standing is performed for 1-2 h, and then the precipitate is filtered out to obtain a mixed solution 2;

[0009] 4) Under stirring, 223A alkaline cyanide-free zinc softening agent, 223B alkaline cyanide-free zinc brightener and 221C alkaline cyanide-free zinc purifier are sequentially added into the mixed solution 2 to obtain a zinc plating solution;

[0010] The concentrations of the solutes in the zinc plating solution are as follows: zinc oxide: (7-13) g / L

[0011] Sodium hydroxide: (120-170) g / L

[0012] 223A Alkaline cyanide-free zinc softener: (8-12) mL / L

[0013] 223B Alkaline cyanide-free zinc brightener: (0.5-1.5) mL / L

[0014] 221C Alkaline cyanide-free zinc purifier: 1 mL / L.

[0015] Advantages

[0016] By using the present application, the following advantages are achieved compared with the conventional zinc plating bath:

[0017] 1) The plating bath is environmentally friendly, green, and has no pungent odor.

[0018] 2) The plating bath is simple to prepare.

[0019] 3) The plating bath has good tolerance to metal impurities, is stable, and is simple to maintain.

[0020] 4) The plating bath has a wide temperature range and current density.

[0021] 5) The plating bath has good throwing and covering power. DETAILED DESCRIPTION

[0022] The present application will be further described below in conjunction with examples.

[0023] Examples

[0024] A total amount of 27 L of plating bath was prepared by using the preparation method of the present application, and the specific method was as follows:

[0025] 9 L of water was added into the tank, 4050 g of sodium hydroxide was weighed and poured into the tank, and stirred to completely dissolve. 297 g of zinc oxide was weighed, adjusted to a paste with water, and added into the alkaline solution under stirring, and after completely dissolved, water was added to 27 L. After the prepared solution was cooled to 32℃, 28 g of zinc powder was added, compressed air was stirred for 40 min, and after standing for 2 h, it was filtered. 270 mL of 223A alkaline cyanide-free zinc softener and 13.5 mL of 223B alkaline cyanide-free zinc brightener were respectively diluted with the plating bath, and then added into the plating bath under stirring, and then 27 mL of 221C alkaline cyanide-free zinc purifier was added. A folding cathode was used as the cathode, and the current was passed for 24 h at 1 A / dm2, and then the plating production was tested.

[0026] Comparative Example

[0027] A total amount of 27 L of plating bath was prepared according to the conventional zinc plating process, and the specific method was as follows:

[0028] In the tank, add 9L of water, weigh 3000g of sodium hydroxide and pour into the tank, stir to dissolve completely. Weigh 200g of zinc oxide, mix with water to form a paste, and add to the tank under stirring, after completely dissolved, add water to 27L. When the prepared solution is cooled to 30°C, add 28g of zinc powder, compressed air stirring for 40min, stand for 2h and filter. Take 216mL of DE additive, 2.7g of MB anti-aging agent, 135g of EDTA, respectively dilute with plating solution and add to the plating solution. Then weigh 13.5g of vanillin, dilute with 200mL of alcohol and add to the plating solution. Use a folded cathode as the cathode, pass a current of 1A / dm2 for 24h, and then test plating production.

[0029] The plating solution obtained in the example and the plating solution obtained in the comparative example are respectively used for galvanizing treatment of tubular steel parts with small holes, and the specific treatment steps are as follows

[0030] The parts are subjected to ultrasonic oil removal (temperature 40°C, time 5min), anode electrolytic oil removal (temperature 80°C, time 10min), hot water washing (temperature 60°C) and flowing cold water washing, then hydrochloric acid pickling (1min), two cold water washings, and then galvanizing surface treatment in the plating solution obtained in the example and the plating solution obtained in the comparative example respectively (temperature 25°C, current density 2A / dm2, plating time 60min), after plating, hot water (temperature 60°C), cold water washing, nitric acid bright dipping (5s), then three-acid passivation (time 5s, air stop 10s), cold water, warm water washing (temperature 40°C), compressed air blowing and drying, and then plating layer inspection.

[0031] The treated parts are subjected to appearance, adhesion strength, plating layer thickness, corrosion resistance and discoloration resistance inspection.

[0032] 1. Appearance

[0033] According to the WJ540-2007 "Specification for Zinc Plating Layer of Steel Parts of Cannonball, Rocket, Missile, Fuse and Firework", the appearance of the plating layer is inspected, and after three-acid passivation, the zinc passivation film is rainbow color, the surface color is basically uniform, and the plating layer is free of defects such as pinhole, pimple, nodule, blister, peeling, dendritic and sponge. The plating layer in the small holes of the parts plated in the plating solution obtained in the example is complete, and the plating layer in the small holes of the parts plated in the plating solution obtained in the comparative example is absent.

[0034] 2. Adhesion strength

[0035] According to the WJ540-2007 "Specification for Zinc Plating Layer of Steel Parts of Cannonball, Rocket, Missile, Fuse and Firework", grid detection is carried out on the parts, and the zinc plating layer at the intersection of straight lines is free of peeling and peeling.

[0036] 3. Plating layer thickness

[0037] The plating thickness was tested according to the point-drop method of WJ545-2007 "Test method for determining the thickness of covering layer of gun shell, rocket shell, missile, fuze and explosive parts". The parts plated in the plating solution obtained in the example were tested to have an outer surface plating thickness of 11.48 μm and an inner surface plating thickness of 10.21 μm; the parts plated in the plating solution obtained in the comparative example were tested to have an outer surface plating thickness of 11.18 μm and an inner surface plating thickness of 8.42 μm.

[0038] 4. Corrosion resistance

[0039] The corrosion resistance was tested according to the test procedure of GJB150.11A-2009 "Environmental test methods for military equipment - Part 11: Salt spray tests", which comprises 96 h of alternating 24 h salt spray and 24 h drying. The parts plated in the plating solution obtained in the example were found to have no corrosion phenomenon in four cycles; the parts plated in the plating solution obtained in the comparative example were found to have black spots on the surface in the third cycle.

[0040] 5. Anti-tarnishing ability

[0041] The parts after plating were placed in an environment of 170°C for 4 h, and it was found that the surface of the parts plated in the plating solution obtained in the comparative example was misted, while the surface of the parts plated in the plating solution obtained in the example was not misted.

Claims

1. A method for preparing an electroplating solution for small-aperture parts, characterized in that: The specific preparation steps are as follows: 1) Pour sodium hydroxide into water and stir continuously to obtain a sodium hydroxide aqueous solution; 2) zinc oxide is mixed with water to form a paste, and the paste is added to a sodium hydroxide aqueous solution under stirring to obtain a mixed solution 1; 3) After the mixed solution 1 is cooled to below 35°C, zinc powder is added, and the mixture is stirred in air for 30-40 minutes. After standing for 1-2 hours, the precipitate is filtered off to obtain mixed solution 2; 4) adding 223A alkaline non-cyanide zinc softener, 223B alkaline non-cyanide zinc brightener and 221C alkaline non-cyanide zinc purifier to the mixed solution 2 in sequence under stirring to obtain a zinc plating solution; The concentrations of the solutes in the zinc plating solution are: zinc oxide: (7-13) g / L Sodium hydroxide: (120-170) g / L 223A alkaline cyanide-free zinc softener: (8-12) mL / L 223B alkaline cyanide-free zinc brightener: (0.5-1.5) mL / L 221C alkaline cyanide-free zinc purifier: 1mL / L.