In order to speed up the alkali etching speed of aluminum profiles, sodium nitrate or sodium nitrite can be added to the alkali etching solution based on sodium hydroxide, and then sodium gluconate and other additives can be added. In addition, there is a tank Factors such as liquid concentration, temperature, and etching time will affect the rate of alkali etching of industrial aluminum profiles and how to control these factors.
Sodium hydroxide is dissolved in water to become an alkaline solution. This solution is usually used as a solution for chemical cleaning tanks for aluminum profiles, that is, an alkaline etching solution. The sodium hydroxide in the alkaline etching solution is all free ions. As the concentration of sodium hydroxide rises to 250g/L, the etching rate of industrial aluminum profiles also increases. It can be seen that the higher the concentration of sodium hydroxide in the bath, the faster the etching rate However, many companies now control the content of sodium hydroxide within the range of 50-100g/L in order to save costs. In order to control the content of sodium hydroxide, you can add gluconate to the bath by adding longevity additives so that the content of free sodium hydroxide is within the range of 70g/L.
The amount of dissolved aluminum
Put the aluminum profile in the alkali solution of sodium hydroxide, and the aluminum and sodium hydroxide will chemically react to form aluminum hydroxide. Affected by the product, the corrosion rate of aluminum will be reduced. Experiments have shown that when the amount of aluminum dissolved is 26g/L When the concentration of sodium hydroxide is 50g/L, the higher the temperature, the slower the etch rate of aluminum. It can be seen that when the bath concentration remains the same, the higher the amount of dissolved aluminum, the slower the etch rate. The amount of instant aluminum is inversely proportional to the etching rate. To obtain the appropriate amount of dissolved aluminum through calculation, pay attention to observe the changes in the bath, and control the amount of dissolved aluminum within the specified range according to the situation.
Through the test of 6063 aluminum profile, we have concluded that as the temperature of the bath rises, the alkali etching rate of aluminum also rises rapidly. Every time the temperature increases by 10°C, the rate of the aluminum etching reaction will double, so the temperature The higher the aluminum profile, the faster the alkali etch rate, which means that the bath temperature is directly proportional to the etch rate. This is because the etching of aluminum profile in alkaline etching solution is an exothermic reaction, which can release 20kw/m² of heat. It is usually necessary to install a cooling device with sufficient cooling capacity to keep the bath temperature at 50-60 Within the range of ℃², this device can be used as a heating device in winter.
In the alkali etching reaction, the longer the etching time of industrial aluminum profiles, the greater the weight loss of aluminum dissolution, and the etching time is not directly related to the etching speed. Shortening the etching time can only reduce the dissolution of aluminum. Weight loss, reduce the consumption of alkali etching agent, which is not proportional to the etching speed. If you want to obtain a smooth aluminum profile surface, you can first process it by mechanical brushing or sandblasting, or by improving mold quality and extrusion The quality of the workmanship can achieve a bright and smooth effect.
Link to this article：Factors Affecting Alkaline Erosion Speed of Aluminum Profiles and Control Methods
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