Four common treatments on the surface of aluminum plate substrates

A Skill requirements for aluminum plate base

The basic skill requirement for the aluminum plate base of the PS plate is that the surface is smooth and flat, without scratches, pits, marks, non-metallic shoe press-in, pores, rolling stripes and other apparent defects. The thickness is consistent, and the wave level is controlled. Within 1mm, the straightness is less than 2I; the structure is fine and uniform, without segregation, slag inclusion, and the internal stress is symmetrical and uniform; the roughness Ra value is less than 0.28 to ensure that the electrolytic sand is fine and uniform. At present, many board-based materials used in our country are 1050A, 1060 and so on.

B alkaline washing

Generally, the aluminum plates supplied by aluminum processing plants have a certain amount of oil on their surface. Oil and oxide film have an impact on the grit disposal. In the production of PS plates, hot alkali is often used to wash the aluminum plates for surface treatment.

Generally, lye is used to remove the oxide film and oil. Commonly used oil removal liquid ratio is: NaOH quality sodium and other corrosion inhibitors and sodium gluconate, fatty acid polyoxyethylene ether solubilization, complexing and other surface active agents.

The temperature of the degreasing liquid is generally controlled at about 55～60℃, and the effect of degreasing is related to the temperature of the solution. If the temperature is too high, the people will seriously corrode the aluminum plate base, so it is necessary to control the temperature.

It is necessary to determine the time of degreasing through careful comparison. Because it is related to various different production lines. The production line of the reel is related to the speed of the production line. Taking 4m/min as an example, the oil removal time must be 20s to ensure its function.

It is necessary to pay attention to the timely update of the oil removal process. Because a lot of saponification, emulsification and aluminum salts are generated during the oil removal process, their existence affects the oil removal effect and prevents the saponification and emulsification of the oil on the surface of the aluminum plate. When the oil is not strong, it is necessary to update it in time. Generally, if the alkali pump is circulated, the degreasing liquid can last a long time, and if it is not circulated, the update time is shortened.

The simpler way to check the degreasing effect is to use water. The surface water of the aluminum plate with good oil removal effect can evenly adhere and loosen. If the water drops on the surface of the aluminum plate, it is in the shape of water droplets, indicating that the oil removal effect is not good. Always pay attention to the temperature of degreasing. If the temperature of the degreasing liquid is too low, it can constitute incomplete degreasing.

C Pickling

In the production process, there is a nitric acid pickling process after alkaline washing, the purpose of which is to remove the residual material after alkaline washing and neutralize the remaining lye. The mass concentration of the nitric acid solution is 5% to 10%. When preparing, pour nitric acid into the water carefully and mix thoroughly. In the pickling process, you should always pay attention to the concentration analysis of the solution and make up in time.

D Coarse

Roughening is to form a grit structure with required roughness. Roughening can not only improve the water affinity of the aluminum base surface, increase the wetting amount of the base surface, and avoid dirt on the plate surface; together, the roughened appearance can also improve the adhesion of the plate to the sensitizer, thereby improving the printing resistance of the printing plate. force.

The roughened sand mesh is composed of countless peaks and valleys. The different sand mesh structure has a greater impact on the adhesion of the water-retaining photosensitive layer and has a greater impact on the use of the PS plate. The production roof is characterized by the characteristic parameters of the rough profile curve of the sand mesh made by the surface roughness tester.