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Nickel pre-coating process and nickel pre-coating solution for magnesium alloy surface

A technology of pre-plating nickel and magnesium alloys, which is applied in hot-dip plating process, metal material coating process, superimposed layer plating, etc. simple effect

Inactive Publication Date: 2007-08-22
HUNAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

They are the same as the galvanizing process proposed by DOW company. After galvanizing, they need to go through cyanide pre-copper plating before electroplating and electroless plating, which has the problem of not being environmentally friendly.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0038] The test material is AZ91D magnesium alloy

[0039] 1. Polishing

[0040] The surface of the magnesium alloy workpiece is treated to a bright surface by mechanical polishing.

[0041] 2. Organic solvent degreasing

[0042] Wash with acetone solvent for 10 minutes under the action of ultrasonic waves, and the operating temperature is room temperature.

[0043] 3. Alkaline washing and degreasing

[0044] Sodium hydroxide (NaOH) 50g·dm -3 , sodium phosphate (Na 3 PO 4 12H 2 O) 10g·dm -3 , temperature: 60±5℃, time: 8-10min;

[0045] 4. Acid corrosion

[0046] Oxalic acid (C 2 h 4 o 2 )10g·dm -3 , sodium lauryl sulfate (C 12 h 25 SO 3 Na), 0.1g·dm -3 , room temperature.

[0047] 5. Alkaline activation

[0048] Potassium pyrophosphate (K 4 P 2 o 7 )40g·dm -3 , potassium fluoride (KF) 5g·dm -3， 75°C, 1min.

[0049] 6. Galvanizing

[0050] Zinc sulfate ZnSO 4 50g·dm -3 , potassium pyrophosphate (K 4 P 2 o 7 )150g·dm -3 , sodium carbonate (Na 2 CO ...

Embodiment 2

[0057] The test material is AZ91D magnesium alloy

[0058] Test procedure is identical with embodiment 1, and pre-plating nickel formula and process condition are: nickel sulfate 25g dm -3 , ammonium citrate ((NH 4 ) 3 C 6 h 5 o 7 )2.5g·dm -3 , ammonium bifluoride (NH 4 HF 2 )35g·dm -3 , Ammonia (NH 3 ·H 2 O) 45cm 3 · dm -3 , pH: 4.5-5.5, temperature: 45-55°C, time: 30min, cathode current density: 2A·dm -2 , air stirring, continuous filtration.

Embodiment 3

[0060] The test material is AZ91D magnesium alloy

[0061] Test procedure is identical with embodiment 1, and pre-plating nickel formula and process condition are: its formula and process condition are: nickel sulfate (NiSO 4 ·6H 2 O) 200g·dm -3 , ammonium citrate ((NH 4 ) 3 C 6 h 5 o 7 )15g·dm -3 , ammonium bifluoride (NH 4 HF 2 )25g·dm -3 , Ammonia (NH 3 ·H 2 O) 35cm 3 · dm -3 , pH: 4.5-5.5, temperature: 45-55°C, time: 6min, cathode current density: 10A·dm -2 , air stirring, continuous filtration.

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PUM

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Abstract

The present invention is nickel pre-coating process and nickel pre-coating solution for the surface of magnesium alloy. The technological process features that magnesium alloy is pre-treated through immersion coating of zinc and then nickel pre-coated, and may be used to replace traditional cyaniding copper pre-coating. The pre-treatment may be any of available zinc immersing processes. The pre-coating solution has nickel sulfate as main component and citrate as accessory ingredient. The present invention has great cathode current range and high current efficiency, and the obtained coating has compact structure, high adhesion and excellent anticorrosive performance.

Description

technical field [0001] The invention relates to a method for pre-plating nickel on a magnesium alloy, which can replace cyanide pre-plating copper, and belongs to the field of metal corrosion and protection. technical background [0002] Magnesium alloy has many unique advantages, such as low density, high specific strength and specific stiffness, and superior damping, machinability, and casting properties. It has been increasingly widely used in the automotive industry, aerospace industry, and electronics industry. Magnesium is rich in raw materials and ranks eighth among natural resources, but as a structural material, its poor corrosion resistance restricts its wider use. [0003] The standard electrode potential of magnesium is -2.37V, which has high reactivity. In air or solution, magnesium alloy will quickly form a very thin passivation film, which will lead to the metal coating and magnesium substrate during electroplating or electroless plating. The adhesion is not ...

Claims

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Application Information

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IPC IPC(8): C23C28/02C23C2/06C25D3/12C25D5/42
Inventor 余刚肖耀坤易祥榕
Owner HUNAN UNIV
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