Dazhi Chemical 315 Alkaline Zinc-Nickel Alloy Process

Since its inception, zinc-nickel alloy has been widely concerned by the electroplating industry because of its unparalleled advantages in corrosion resistance. With the continuous development of zinc-nickel alloy, it has been used in hardware, automobile, electronics, aerospace and other fields.

Guangdong Dazhi Chemical Technology Co., Ltd. according to the application of the market, timely summary of the problems in production, and targeted to solve after the introduction of a new electroplatingHKS-315 alkaline zinc-nickel alloy electroplating process. After the successful development of the product, it did not immediately carry out large-scale promotion in the market, but carried out production tests through our cooperative electroplating company. Through the small test, pilot test and large-scale production in recent years, through the continuous improvement of products, HKS-315 alkaline zinc nickel alloy plating process is a mature and stable process. It has the advantages of excellent corrosion resistance of the coating, easy operation, simple management, and easy purification of various colors.

315 alkaline zinc-nickel alloy process additives mainly include fining agent, stabilizer, supplement.

The role of each component and process parameters in the plating solution.

1. Metal ions

The metal ions refer to zinc ions and nickel ions. Zinc ions have a great influence on the current efficiency of the plating solution; increasing the mass concentration of zinc ions can improve the current efficiency of the plating solution. Too high will affect the appearance of the product, the coating is gray, dark, stripes in the middle and low areas, and reduce the mass fraction of nickel in the coating; too low will make the coating dark and roughness increase. In addition, the nickel in the coating will also change with the mass concentration of zinc ions.(as a function of the ratio of zinc ions to nickel ions). In order to conveniently control the mass fraction of nickel in the plating layer, it is necessary to strictly control the mass concentration of nickel ions in the plating solution. If the mass concentration of nickel ions is too high, the coating will be dark and the low position will be black. If the mass concentration of nickel ions is too high, the high position will be grayish yellow and dull, and the middle and low positions will be gray and white. Zinc ions in the plating solution need to be analyzed once in 8h. Zinc ions are added by dissolving the zinc plate in a separate zinc dissolving tank outside the tank. Nickel ions need to be analyzed once a day. Nickel ions are added according to the amount of electricity to supplement the automatic dosing equipment. In order to ensure the stability of the mass concentration of nickel ions, it is necessary to explore the consumption suitable for the production line on site to continuously adjust the amount of automatic dosing equipment.

2

On the one hand, NaOH is a complexing agent of zinc ions; on the other hand, it acts as a conductive salt of the solution, which can reduce the solution resistance and improve the dispersion ability of the plating solution. NaOH helps to form a white and dense coating, and its low mass concentration will cause the coating to turn black, form a sponge-like coating, high roughness, etc. NaOH will affect the nickel in the coating to a certain extent. Too high and too low are not conducive to the quality of the coating, so it needs to be analyzed once a day and adjusted in time.

3. Stabilizer

The stabilizer helps maintain a uniform alloy composition of the coating. With the increase of its volume fraction, the nickel in the coating will be slightly increased accordingly; excess will reduce the current efficiency. The stabilizer is added through an automatic dosing device that is added according to the amount of electricity. In order to ensure a stable volume fraction, it is necessary to explore the consumption suitable for the production line on site to continuously adjust the addition amount of automatic dosing equipment.

4. Fine crystal agent

The function of the fining agent is to make the mirror layer crystal fine. Excess of the grain fines will reduce the current efficiency. The fine crystal is added by an automatic dosing device that is added according to the amount of electricity. In order to ensure a stable volume fraction, it is necessary to explore the consumption suitable for this production line on site to continuously adjust the addition amount of automatic dosing equipment.

5. Temperature

The temperature range of HKS-315 alkaline zinc-nickel alloy electroplating process is very wide, and qualified coatings can be obtained from 10 ℃ to 40 ℃. However, if the temperature is too low, the current efficiency will decrease. In order to be suitable for the actual production of the factory, the operating temperature is controlled at 20 ℃ ~ 35 ℃.

6. Current density

The current density range of the HKS-315 alkaline zinc-nickel alloy electroplating process is very wide, and satisfactory coatings can be obtained from 0.25A/dm2 to 5A/dm2. The current density is large, and the high position will not be burnt; the current density is small, and the effect around the low position is OK.

7. Anode

The anode of HKS-315 alkaline zinc-nickel alloy plating process adopts nickel-plated iron plate or electrolytic nickel plate. Taking into account the cost of the problem, the general selection of nickel-plated iron as the anode. It is different from the use of zinc plate or zinc plate and nickel plate as anode in some electroplated nickel alloy process. This has the advantage of avoiding the occurrence of high concentration of bath solution or high local concentration and uneven.

When the guaranteed coating thickness is greater8um in the case of blue, black, color, white passivation. After the passivation is placed for 24h, the neutral salt spray test is carried out. The test results can completely reach the white rust time of more than 300h and the red rust time of more than 1000h.

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