HL-93 Potassium Chloride Zinc-plating Additives B

HL-93 potassium chloride zinc-plating additives A

HL-93 high cloud point potassium chloride zinc-plating brightening agent

Packing specifications: 25kg/plastic drum

                                                    200kg/plastic drum

                                                    1000kg/plastic drum on metal pallet

 

The coating has high brightness, low brittleness, turbidity point of the bath can reach more than 80℃, and bright coating can be plated at 65℃. Its comprehensive performance can be completely comparable with similar foreign products.

 

1.Zinc Chloride

Zinc chloride as the main salt, is also a conductive salt, it in the plating solution all ionized into chloride ions and zinc ions, ionized zinc ions will be directly on the plating part of the cathode reduction into a coating, can increase the conductivity of the plating solution, its concentration allowed to change in a wide range. It is easy to absorb moisture, easy to dissolve, exothermic phenomenon.

 

Zinc chloride provides zinc ions. When the content of ZnCl12 is set to the upper limit, the cathode current density can be improved and the deposition rate of the coating can be improved, but the dispersion ability and covering ability become worse. When the content of ZnCl12 is set to the lower limit, the dispersion ability can be improved, the loss of the plating parts taking out liquid and the cost of tank fitting and wastewater treatment can be reduced. When the content of ZnCl12 is too low, the concentration polarization will be large, resulting in low current opening, which will narrow the bright area of the plating, decrease the cathode current density accordingly, slow down the deposition rate, and prone to charring phenomenon in the high current density area of the plating.

 

In the production practice, as long as the additive selection is appropriate, the content of zinc chloride can be increased, even if the current density is increased, the coating will not appear burning phenomenon on the surface of the plating, so as to ensure the quality of the coating and improve the output.

 

For the matrix metal that is difficult to electroplate, such as cast iron, the zinc content should be upper limit to increase the cathode limit current density, and the zinc content should be lower limit in summer.

 

The concentration of zinc chloride can vary in the range of 40-80g/L, in principle, the content of hanging plating is lower than that of rolling plating. If there is a hanging bath with moving cathode, the content of zinc chloride should be 45-60g/L. If there is no cathode moving device, the content of zinc chloride should be 60-80g/L. According to experience, the loss of 1 ton parts per plating is 4-5 kg.

 

2.Zinc Chloride characters:

High zinc chloride content: can improve cathode current density and cathode current efficiency

Reduce dispersion and coverage

High content makes the coating rough easily

Low zinc chloride content: can appropriately improve the dispersion ability

When it is too low, the concentration polarization will increase, the current will not open much, the upper limit of the current density will decrease, the high current density area will appear charring phenomenon, and the bright area will narrow.

 

Although chloride ion has a weak coordination effect on zinc, potassium chloride in the solution in addition to play a conductive role in an active anode, that is, to promote the anode normal solvent. The concentration is generally controlled in 200-280g/L. The content of potassium chloride in the bath is high, the conductivity of the bath is good, but too high will affect the solution of additives in the bath, so that the brightness of the coating decreases. The concentration of potassium chloride is too high, the crystallization will be precipitated below 5℃ in winter. The concentration of potassium chloride is too low, not only the conductivity is poor, but also the dispersion and covering ability of the plating solution is reduced, the brightness of the coating is poor, and the range of current density is narrow. KCL should be analyzed and supplemented regularly. General KCL concentration is controlled at about 240g-260g/L. According to the experience of plating 1 ton parts to take out 5-7 kg.

 

High content: good conductivity, small resistance, good dispersion ability, anode is not easy to passivation.

Too high: there will be crystallization in winter, little improvement on the electroconductivity of the bath.

Low content: the concentration of potassium chloride is too low, not only the conductivity is poor, and the dispersion ability is reduced, the coating brightness is poor, but also affect the range of cathode current density

Potassium chloride has weak complexation on zinc.

 

The main function of boric acid H3BO3 is to inhibit the increase of PH value of the bath, so that the bath PH value remains relatively stable, and the coating can be uniform and bright. When boric acid content is insufficient, the range of cathode current density will be reduced, the current is not open, the coating is easy to burn, resulting in rough gray coating and loss of light. In order to stabilize PH value of bath, it is necessary to maintain proper boric acid content. But the boric acid content should not be too high, if the content is too high, the coating will blossom, so at the general temperature, more than 45g/L will crystallize and precipitate. So the appropriate boric acid content is 30-40g/L, winter to take 30g/L is appropriate, summer boric acid content can be increased to 35-40g/L.

 

In addition, we should pay attention to the quality of boric acid and prevent the interference of nitrate and other factors.

Note: The brightness of the galvanized layer caused by the lack of boric acid is not enough, and the addition of brightener is of no avail. But after the addition of boric acid, the coating is immediately bright, which is the defect caused by the poor buffering performance of the plating solution of boric acid. Therefore, the role of boric acid must not be ignored in production, and its content should be guaranteed within the process range. In daily production, when the PH value of the bath changes quickly, it indicates that the boric acid content in the bath has been low, and it needs to be added. Boric acid is only taken out of consumption. As a rule of thumb, you only need to supplement boric acid with potassium chloride. The supplement amount is 1/7 of the weight of potassium chloride, that is, for every 7 kilograms of potassium chloride, you need to also add 1 kilogram of boric acid. In addition to boric acid should be fully dissolved after adding, otherwise it can not play its due role.

 

Stabilize the PH value of the bath to prevent the PH value from rising too fast

Boric acid content is too high: because boric acid solubility is small, easy to crystallize in winter, generally controlled at about 30g/L.

Low boric acid content: the PH value is increased, the main salt is easy to hydrolyze, metal ions to form hydroxide or basic salt in the coating, resulting in rough coating.

 

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