Why are there black spots on the surface of 5052 aluminum plates?

The aluminum plate is divided into pure aluminum plate, alloy aluminum plate, thin aluminum plate, medium thickness aluminum plate and pattern aluminum plate. 5052 aluminum plate used in buildings includes single-layer aluminum plate, composite aluminum plate and other materials. Generally, it often refers to single-layer aluminum plate, which is mostly used in architectural decoration engineering. In recent years, single-layer aluminum plates are more commonly used in aluminum plate curtain walls. The aluminum plate supplier shall analyze the causes of black spots on the aluminum plate surface.

The first is the material of 5052 aluminum plates. The upper cover of the aluminum plate produced by the aluminum plate manufacturer is processed from LF21 aluminum plate with a thickness of 0.5mm. This type of aluminum plate has a variety of parts with the same material, similar shape and same process, but the parts with similar shape processed at the same time do not have such faults. And this is not the fault caused by the defect of raw materials. In terms of processing technology, the general process route of silver plating on the upper cover is: Machining incoming parts - Pretreatment - zinc dipping - electro galvanizing - copper electroplating - silver plating - Painting - dip coating 823 - warehousing.

5052 aluminum plates

In the process of 5052 aluminum plate electroplating, first of all, there may be a change in a production link of electroplating, resulting in failure. However, the investigation found that similar parts processed in the same period did not have such faults without any change in production conditions. Therefore, the factors affecting the change of electroplating production conditions are excluded. According to previous production experience, the most common cause of discoloration of silver plated parts is the influence of sulfur on silver plated layer.

In the past, it happened that the silver plated parts were not packaged and sealed in time, and were placed in the electroplating plant for a long time, resulting in the yellowing of the silver plating layer. However, after silver plating, the faulty parts were timely packed and stored in dry vessels. It can be seen that this is not affected by the air atmosphere of the plant. In terms of painting process, it was found that the painting process of the upper cover had been repaired in a whole batch. The most important reason is that the gap is not blocked, allowing the paint mist to enter and adhere to the surface of the silver plating layer. In order to prevent such faults, it is recommended to seal the gap with tape during processing to prevent paint mist from entering.

Through this elimination method, the root cause of the problem is found. Measures should be taken to eliminate the recurrence of hidden dangers, so that the surface of aluminum plate is as bright as new, and the delivery rate is greatly improved.