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Non-cyanide electroplating process for zinc alloy die casting

An electroplating process and die-casting technology, which is applied in the new non-cyanide electroplating process field of zinc alloy die-casting parts, and can solve the problems of limited large-scale application, poor bonding force between the nickel-plated layer and the substrate, and poor activation ability.

Inactive Publication Date: 2004-02-11
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] Neutral nickel pre-plating is mainly used for the rack plating process of zinc alloy die castings, and the main component of the plating solution is NiSO 4 , sodium citrate, etc., do not contain cyanide, but the bonding force between the nickel plating layer and the substrate is far inferior to the performance of cyanide copper plating pre-plating, and the product qualification rate is low
Moreover, due to the poor activation ability of the neutral nickel plating solution on zinc alloy die castings, there are higher requirements for its pretreatment
The neutral nickel plating process generally cannot be used for barrel plating of zinc alloy die castings, therefore, the range of industrial applications is not very wide
In addition, the cost of neutral nickel plating solution is high, and wastewater treatment is difficult, which limits its large-scale application in industry.
[0007] Other zinc alloy die casting pre-plating processes include chemical copper plating, HEDP copper plating, copper-tin alloy electroplating, etc., all of which have not been practically applied in industry due to problems such as bonding force, cost, and wastewater treatment.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0014] The composition and process conditions of zincate galvanizing in zincate galvanizing pre-plating process: zinc oxide 6g / L, sodium hydroxide 100g / L, brightener 4ml / L; solution temperature 10°C; cathode current density during electroplating 1A / dm 2 , start the cathode current density 3A / dm 2 ; Plating time 15min.

[0015] The solution composition and process conditions of the slightly acidic electroless nickel plating process: nickel sulfate 10g / L, sodium citrate 5g / L, sodium hypophosphite 14g / L, ammonia water adjusted to the specified pH value, ammonium bifluoride 6g / L; The pH value is 6.5; the solution temperature is 75°C; the electroplating time is 20min.

[0016] Zinc alloy die castings are subjected to the above-mentioned alkaline pre-galvanizing and slightly acidic electroless nickel plating, followed by conventional pyrophosphoric acid copper plating for 20 minutes, acid copper plating for 15 minutes, and bright nickel plating for 15 minutes. , cooled to room t...

Embodiment 2

[0018] The composition and process conditions of the zincate galvanizing solution in the zincate galvanizing pre-plating process are: zinc oxide 10g / L, sodium hydroxide 140g / L, brightener 8ml / L; electroplating temperature 40°C; cathodic current during electroplating Density 3A / dm 2 , start the cathode current density 7A / dm 2 (15 ~ 30s); electroplating time 25min.

[0019] The solution composition and process conditions of the slightly acidic electroless nickel plating process are: nickel sulfate 16g / L, sodium citrate 9g / L, sodium hypophosphite 22g / L, ammonia water adjusted to the specified pH value, ammonium bifluoride 10g / L ; pH value is 7.5; solution temperature is 85°C; electroplating time is 30min.

[0020] Zinc alloy die castings are subjected to the above-mentioned alkaline pre-galvanizing and slightly acidic electroless nickel plating, followed by conventional pyrophosphoric acid copper plating for 20 minutes, acid copper plating for 15 minutes, and bright nickel plat...

Embodiment 3

[0021] Embodiment three (preferred embodiment):

[0022] The composition and process conditions of the zincate galvanizing solution in the zincate galvanizing pre-plating process are: zinc oxide 8g / L, sodium hydroxide 120g / L, brightener 6ml / L; solution temperature 25°C; cathodic current during electroplating Density 2A / dm 2 , start the cathode current density 5A / dm 2 (20s); electroplating time 20min.

[0023] The solution composition and process conditions of the slightly acidic electroless nickel plating process are: nickel sulfate 13g / L, sodium citrate 7g / L, sodium hypophosphite 18g / L, ammonia water adjusted to the specified pH value, ammonium bifluoride 8g / L ; The pH value is 7.0; the solution temperature is 80°C; the electroplating time is 25min.

[0024] Zinc alloy die castings are subjected to the above-mentioned alkaline pre-galvanizing and slightly acidic electroless nickel plating, followed by conventional pyrophosphoric acid copper plating for 20 minutes, acid cop...

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Abstract

The non-cyanide electroplating process for zinc alloy die casting includes first pre-plating with zincate and then subacid chemical nickel plating. In the pre-plating with zincate, the plating solution comprising zinc oxide, sodium hydroxide and brightener is used, the electroplating temperature is 10-40 deg.c, electroplating current is 1-7 A / sq dm and electroplating time is 15-25 min. In the subacid chemical nickel plating, the plating solution comprising nickel sulfate, sodium citrate, sodium hypophosphorite, ammonia water and hydrogen ammonium fluoride and with pH 6.5-7.5 is used, the solution temperature is 75-85 deg.c and the electroplating time is 20-30 min. The technological process of the present invention is used to replace cyanide copper-plating process and has no pollution caused by cyanide and low waste water treating cost.

Description

technical field [0001] The invention relates to a new non-cyanide electroplating process for zinc alloy die castings. Zinc alloy contains 3-5% aluminum, 1.0-1.7% copper, about 0.04% magnesium, and the rest is zinc. Background technique [0002] Due to its cheap price, low melting point, and especially good die-casting process performance, zinc alloy has been widely used in the manufacture of small hardware accessories, and can also be used to manufacture decorative and practical metal parts. Such as various zippers, belt buckles, luggage accessories, car nameplates and military badges, etc. [0003] The appearance of zinc alloy die castings is gray and white, and there are various defects on the surface, such as: slag inclusions, shrinkage cavities, etc. Therefore, without surface treatment, its usability and decoration are very poor. A common surface treatment method is electroplating. According to the different decorative and functional requirements, there are certain d...

Claims

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Application Information

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IPC IPC(8): C23C28/02
Inventor 何建平张永亮
Owner NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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