High storage temperature and humidity

After the electrolytic copper foil is rolled up and down in the electrolytic cell, oxidation reaction will occur on the surface due to incomplete drying of the rough surface and prolonged storage time. If the storage environment has high temperature or humidity, the oxidation rate of the copper foil surface will accelerate, which will be severe. In summer, copper foil is rolled down from the electrolytic cell in northern China and will oxidize within 6 hours without surface treatment. Sometimes, after 6 hours of production in the electrolytic cell, the copper foil has already begun to oxidize before being rolled down.

Sometimes in the south, after the copper foil is peeled off from the surface of the cathode roller, it has already oxidized before being rolled up. When the temperature is low and the climate is dry, copper foil can be stored for ten days or even half a month without any problem. The main reason for the oxidation of the surface of the raw foil is the air temperature and humidity. Under normal circumstances, there is a correlation between air temperature and humidity.

The air temperature is high, and the moisture content in the air is also high. Air molecules are active, and copper foil is very prone to oxidation. Whether in the south or north, copper foil has oxidation problems in summer, and the south is more prone to oxidation due to high temperatures and humidity.

resolvent:

1. Introduce dry hot air into the winding box to keep the copper foil in a high-temperature and dry environment at all times;

2. Spray the surface of the raw foil with benzotriazole anti oxidation solution;

3. Do not roll the foil too big in summer. Copper foil with larger rolls will be corroded by static electricity for a long time, and the edges will be severely oxidized due to prolonged exposure to air corrosion.

4. After the copper foil is removed from the electrolytic cell, it should be immediately processed on the surface treatment line to avoid oxidation of the copper foil surface after prolonged storage. When organizing production, the next roll of foil should be planned according to the processing speed of the processing line. After the next roll, it should be immediately put on the surface treatment line for production, so as not to store the foil for too long or not at all. It is not possible to finish the surface treatment of copper foil immediately, and the fastest time is 4-5 hours (30m/min).

High temperature and humidity in the production workshop

The temperature and humidity in the production workshop are high, and the electrolytic copper foil oxidizes quickly after being produced in the electrolytic cell. The surface oxidation of the copper foil was already very severe when it was offline. So the temperature in the electrolysis workshop during summer should not exceed 25 degrees Celsius, and the humidity should not exceed 40%. It is better if the two indicators are too low.

The most important thing is to keep the workshop dry, such as keeping the floor dry and free of water, not using water to mop the floor, and not setting up water pools or faucets in the workshop. Ensure that all the humid gases generated by the electrolytic cell and grinding rollers are discharged from the workshop.

Ensure the sealing of the first and second floors of the factory building to prevent humid air from entering the second floor electrolysis workshop, especially acidic humid and hot air, which must not enter the second floor electrolysis workshop.

During the design of the factory building, it is necessary to ensure that the air conditioning supply has appropriate return air. When the outdoor air humidity is high, return air can be used as the main source, supplemented by fresh air supply. When the outdoor air humidity is particularly high, the fresh air must be dehumidified or not used to maintain the workshop humidity at a low level. The doors and windows of the factory must be sealed, preferably insulated. It is better for the temperature in the foil production workshop to be low and the humidity to be low.

Spray washed copper foil position

After the copper foil is transferred out of the electrolyte of the electrolytic cell with the cathode roller, the surface of the copper foil should be immediately sprayed with electrolyte to remove surface attachments (organic additives).

The closer the spraying position is to the liquid level in the electrolytic cell, the better. If the distance is large, the electrolyte will be exposed to air for a long time, which can easily produce acid mist. It is also easy to cause the electrolyte squeezed off the surface of the copper foil to flow down along the copper foil, forming small liquid flows in many places, which can cause acid channels on the surface of the copper foil.

Moreover, the greater the distance between the extrusion roller and the liquid surface, the longer the downward flow time, because the presence or absence of liquid on the surface of the copper foil will result in different corrosion strengths, and the longer the time, the greater the color difference caused by corrosion. The corrosion intensity is lower in areas without liquid flow and higher in areas with liquid flow, causing more severe corrosion on the copper foil surface. The degree of corrosion varies, and the color and roughness of the copper foil surface are different.

Severe corrosion can cause acid channels on the surface of copper foil (in fact, the copper foil surface may contain acid). The acid stains on the rough surface will be printed on the smooth surface of the copper foil after winding, affecting the appearance quality of the copper foil. The closer the squeezing roller (also known as the water receiving roller) is to the liquid level of the electrolytic cell, the better. If the distance is too large, the electrolyte squeezed down by the squeezing roller will flow downwards for too long, causing acid channels.

The thinner the copper foil, the faster the cathode roller speed, and the more liquid is carried on the surface of the copper foil (because the copper foil is in contact with the electrolyte on the rough surface). The more liquid is squeezed out, the more acid channels on the surface of the copper foil, and the more severe the corrosion of the rough surface, which has a more serious impact on the smooth surface of the copper foil.

Surface washing process of copper foil

The copper foil comes out of the electrolytic cell and needs to be washed with water in the shortest possible time after being squeezed by the squeezing roller. It is better to have the washing position close to the squeezing roller, so that the water can flow evenly on the surface of the copper foil and the contact time between the copper foil surface and the electrolyte is consistent.

As the distance increases, it is impossible to form a sheet-like water flow. Naturally, it will gather into multiple water flows in one direction and flow downstream in several directions. With a larger distance, the water flow will last longer, causing an increase in the color difference between areas with and without water flow on the surface of the copper foil. This type of waterway is black in color. The surface of copper foil needs to be washed with a certain amount of pressure and water, and sufficient water pressure can ensure that the residual liquid in the extremely small pits on the surface of the copper foil is washed clean.

Adequate water is used to flush away residual liquid and impurities from the micropores on the surface of the copper foil, preventing them from remaining on the copper foil and causing corrosion and stains. The quality of water for washing is crucial. There must be no chloride ions, acid, or oil in the water, and it must be pure water.

The pH value must be neutral. If the surface of the copper foil is not washed clean, the copper foil is easily oxidized. The cleaner the surface is washed, the better the anti oxidation effect of the copper foil. If the surface of the copper foil is washed very clean and dried very dry. When stored, even if the temperature and humidity are higher in summer and the storage time is longer, copper foil is not easily oxidized.

Exhaust effect of electrolytic cell

The poor design of the exhaust position of the electrolytic cell prevents the acid gas from being discharged. The acid gas overflowing from the electrolytic cell vertically fumigates the smooth surface of the copper foil, causing oxidation of the copper foil surface.

If the overflowing acid gas meets the humid air in the workshop, it condenses into acid mist and drips onto the copper foil, forming acid mist corrosion points, which are the acid mist points on the copper foil. The exhaust of the electrolytic cell is carried out by a large induced draft fan, and a large amount of air in the workshop is extracted through the electrolytic cell exhaust outlet to achieve the replacement of air in the workshop.

The exhaust outlet of the electrolytic cell is also the exhaust outlet of the workshop air, and the area with the highest air discharge volume in the workshop. Therefore, the exhaust outlet of the electrolytic cell cannot be too close to a certain position on the surface of the cathode roller, in order to reduce the wind corrosion of the cathode roller surface by the airflow. Titanium cathode rollers are not afraid of immersion in electrolyte, but rather of air blowing.

The exhaust port should not be directly connected to the return port to reduce the amount of electrolyte carried out by the wind, prevent the exhaust port of the electrolytic cell from being blocked due to copper sulfate crystallization, and reduce the amount of copper sulfate solution brought into the air duct, which may cause copper sulfate crystallization. Once this situation occurs, production should be stopped for cleaning.

Article source: Internet