What is the working principle of the chrome bottle?

During electroplating, the chromed bottle coating metal is used as an anode and oxidized into cations into the electroplating solution; the metal product to be plated is used as a cathode, and the cations of the coating metal are reduced on the metal surface to form a coating. In order to eliminate the interference of other cations and make the coating uniform and firm, it is necessary to use a solution containing the coating metal cations as the electroplating solution to keep the concentration of the coating metal cations unchanged. The purpose of chromed bottle hard chrome plating is to plate a metal coating on the substrate to change the surface properties or size of the substrate. chromed bottle can enhance the corrosion resistance of the metal, increase the hardness, prevent abrasion, improve conductivity, lubricity, and heat resistance.

Here is the content list:

What is the principle of hard chrome plating for making chromed bottle?

What are the process conditions for hard chrome plating in chromed bottle?

What are the characteristics of the hard chrome plating process in chromed bottle?

What is the principle of hard chrome plating for making chromed bottle?

When making the chromed bottle, in the plating tank containing the electroplating solution, the cleaned and specially pretreated parts to be plated are used as the cathode, and the anode is made of plated metal, and the two poles are respectively connected with the negative and positive electrodes of the DC power supply. The electroplating solution is composed of an aqueous solution containing metal-plated compounds, conductive salts, buffers, pH adjusters, and additives.

After electrification, the metal ions in the electroplating solution move to the cathode under the action of the potential difference to form a plating layer. The anode metal forms metal ions into the electroplating solution to maintain the concentration of the plated metal ions. In some cases, such as chromium plating, an insoluble anode made of lead and lead-antimony alloy is used, which only serves to transfer electrons and conduct current.

A technology that uses electrolysis to deposit a metal coating with good adhesion on the chromed bottle, but with different properties from the base material.

The plating layer of chromed bottle is more uniform than the hot dip layer, generally thinner, ranging from a few microns to tens of microns.

Through electroplating, decorative protection and various functional surface layers can be obtained on the chromed bottle, and the chromed bottle that is worn and processed can be repaired.

The chromed bottle coating is mostly a single metal or alloy, such as titanium target, zinc, cadmium, gold or brass, bronze, etc.; there are also dispersion layers, such as nickel-silicon carbide, nickel-graphite fluoride, etc.;

There are also cladding layers, such as copper-nickel-chromium layer on steel, silver-indium layer on steel, etc.

In addition to iron-based cast iron, steel and stainless steel, the electroplating base material also has non-ferrous metals, such as ABS plastic, polypropylene, polysulfone, and phenolic plastic. However, the plastic must undergo special activation and sensitization treatment before electroplating.

What are the process conditions for hard chrome plating in chromed bottle?

In the chromed bottle chrome plating process, there is a mutual dependence between cathode current density and temperature. When chromium plating in the same solution, by adjusting the temperature and current density, and controlling them within an appropriate range, three different chromium plating layers of bright chromium, hard chromium and opal chromium can be obtained.

In the low-temperature and high-current-density area, the chromium coating is gray or scorched. This coating has network cracks, high hardness and high brittleness; in the high-temperature and low-current density area, the chromium layer is milky white, with fine structure, few pores and no Cracks, good protection performance, but low hardness, poor wear resistance; when the middle temperature and middle current density area or the two are better, a bright chrome layer can be obtained. This chromed bottle chrome layer has higher hardness and has a fine and dense mesh Crack.

When the current density is constant, the current efficiency decreases with the increase of temperature; if the temperature is fixed, the current efficiency increases with the increase of the current density. However, when the ratio of chromic anhydride to sulfate ion decreases, the change becomes smaller accordingly.

Therefore, when chromed bottle is plated with hard chromium, under the premise of meeting the performance of the coating, lower temperature and higher cathode current density are usually used to obtain a higher deposition rate of the coating. When the temperature is constant, as the current density increases, the dispersion ability of the plating solution is slightly improved, so the temperature and current density must be strictly controlled.

What are the characteristics of the hard chrome plating process in chromed bottle?

In addition to the commonality of chromed bottle chrome plating process with other plating species, there are many special places:

① The main component of chromed bottle chrome plating electrolyte is not metal chromium salt, but chromic acid with strong oxidizing properties.

② The current efficiency is very low, generally 13-16%, and the highest can only reach about 23%. Therefore, a large amount of hydrogen is precipitated during the chromed bottle chrome plating process, which brings out toxic liquid mist. A good suction device and chrome mist suppression are required. Agent.

③ A small amount of external anions must be added to the solution, such as SO42-, F-, SiF62-, etc., and a certain amount of trivalent chromium must be maintained in the electrolyte.

④ The dispersing ability is low. For parts with more complicated shapes, pictographic anodes, protective cathodes, etc. must be used to get a good coating.

⑤ The current density used is very high, sometimes tens of times higher than the current density of general plating. The tank voltage of the chromed bottle chrome plating process is also high, and it is often necessary to use a power supply above 12 volts, while other plating types can use a 6 volt power supply.

⑥ The temperature and current density control requirements are strict, and the two must be closely coordinated. The current density is fixed, and the temperature can only vary by 1 to 2°C, while the temperature is fixed, and the current density can vary by 2 to 3A/dm2.

⑦ The anode used in chromed bottle chrome plating is not metallic chromium, but insoluble anodes such as lead, lead-tin alloy or lead-antimony alloy.

⑧ Because the chromium layer is easy to passivate, in general, it is not allowed to cut off the power during the electroplating process.

The above points reflect some of the characteristics of the production of chrome-plated chrome bottles, that is, their particularity. This particularity constitutes the special essence that distinguishes the chrome plating process from other electroplating processes. However, chrome plating is a kind of electroplating. Of course, it also has general rules for electroplating. We should start with production practice and gradually study and understand the whole process of chrome plating of chrome bottles. You can also contact the dedicated Gensyu team to understand and master the special and general chrome-plating process of chrome bottles!