Metal Plating

Jul 09, 2019

Electroplating is an electrochemical process and a redox process. The basic process of electroplating is to immerse the part in a solution of metal salt as a cathode, and the metal plate as an anode, after the DC power supply, Plating deposits the required on the part.

The process of electroplating is basically as follows:

The plated metal is at the anode and the material to be plated is at the cathode.

The anode and cathode are connected by an electrolyte solution composed of plated metal positive ions.

After passing through the DC power supply, the metal of the anode will oxidize (loss electrons), and the positive ions in the solution will be reduced (obtained electrons) at the cathode to form atoms and accumulate on the surface of the cathode.

The appearance of the plated object after electroplating is related to the magnitude of the current. The smaller the current, the more beautiful the object to be plated; otherwise, the uneven shape will appear.

The main uses of electroplating include preventing metal oxidation (such as rust) and decorating.

The role of electroplating:

1. Copper plating: used as a primer to improve the adhesion of the plating layer and the ability to resist corrosion.

2. Nickel plating: base or appearance, improve corrosion resistance and wear resistance, (where chemical nickel is more resistant to chrome in modern processes).

3. Gold plating: Improve the conductive contact resistance and improve signal transmission.

4. Palladium-plated nickel: Improve the conductive contact resistance, improve signal transmission, and wear resistance higher than gold.

5. Tin-plated lead: Improves the welding ability and is quickly replaced by other substitutes.

6. Silver plating: Improve the conductive contact resistance and improve signal transmission.

Electroplating is a method of laying a layer of metal on a conductor using the principle of electrolysis. In addition to electrical conductors, electroplating can also be used on specially treated plastics.

Take nickel plating as an example:

When nickel plating, the cathode is the part to be plated, the anode is a pure nickel plate, and the following reactions occur in the anode and the cathode respectively:

Cathode (plated): Ni2++2e-→Ni (main reaction)

2H++2e→H2↑ (side reaction)

Anode (nickel plate): Ni -2e→Ni2+ (main reaction)

4OH--4e-→2H2O+O2 (side reaction)

New insoluble electrode - titanium anode:

The titanium anode has high electrochemical catalytic energy, and the oxygen evolution overpotential is about 0.5 V lower than the lead alloy insoluble anode. The energy saving is remarkable, the stability is high, the plating solution is not polluted, the weight is light, and the replacement is easy.

Advantage:

1. The oxygen evolution overpotential of the titanium anode is also lower than that of the platinized anode, but the lifetime is increased by more than 1 time;

2. It can reduce the tank voltage and save power consumption;

3. Titanium anode has good stability (chemical, electrochemical) in the electroplating process and has a long service life.

The use of titanium electrodes in the electroplating industry generally selects coatings with rare metal oxides, such as tantalum coatings, tantalum coatings, and the like.

Application of rare metal oxide coating titanium anode in electroplating

The rare metal oxide coating titanium anode is made of precious metal strontium salt coated on a titanium substrate and sintered at a high temperature, and is widely used in the hydrometallurgy industry such as electroplating and electrolysis. The preparation and application of noble metal oxide coated titanium anodes are quite mature. The advantages of such titanium anodes are as follows:

1.High current efficiency, excellent corrosion resistance, long anode life and high current density.

2.energy saving: precious metal oxide coating titanium anode is a low oxygen evolution overpotential electrode, it is easier to analyze oxygen in the oxygen evolution zone of the anode. Therefore, the cell pressure is also relatively low during electrolysis, which saves energy.

3.No pollution: noble metal oxide coating Titanium anode coating is a ceramic oxide of noble metal niobium, which is a fairly stable oxide.

4.cost-effective: In order to achieve the same service life of the platinized electrode, the price of the precious metal oxide coating titanium anode is about 80% of the platinized electrode.

5.low maintenance cost: compared to the traditional soluble electrode, the precious metal oxide coating titanium anode does not need to change the anode bag frequently and re-plating the anode, so the productivity is improved, the labor cost is reduced;

6.Under the same working conditions, the life of the noble metal oxide coated titanium anode depends on the working current density, temperature and bath composition.