What are the specific precautions for surface pretreatment of embossed aluminum plate with imitation wire drawing pattern?

It is very important for you to pay attention to surface pretreatment, which directly determines the effect of subsequent wire drawing and embossing and the adhesion of surface coating, and is the basic step to ensure product quality. Pretreatment needs to focus on controlling cleanliness, corrosion and surface smoothness, and the core considerations can be divided into three core dimensions.

I. Matters needing attention in chemical cleaning

Chemical cleaning (degreasing and descaling) is the core of pretreatment, and the parameters need to be accurately controlled to avoid damaging the aluminum substrate or residual impurities.

Concentration and temperature control of degreasing agent: When alkaline degreasing agent (such as sodium hydroxide solution) is selected, the concentration should be controlled at 5%-10% and the temperature should be kept at 50-70℃. Excessive concentration or high temperature will lead to excessive corrosion and pitting on the surface of aluminum plate; If the concentration is too low or the temperature is not enough, the rolling oil stain can not be completely removed, and the texture will be uneven in the subsequent drawing.

Control of cleaning time: the soaking time of aluminum plate in degreasing agent should be controlled at 3-5 minutes, which should be adjusted according to the severity of oil pollution. If the soaking time is too short, the oil residue will affect the subsequent process; If it is too long, it may lead to slight corrosion at the edge or weak part of aluminum plate, which will affect the surface flatness.

Thoroughness of neutralization treatment: after degreasing, it should be soaked in acidic neutralization solution (such as nitric acid solution with concentration of 3%-5%) for 1-2 minutes to neutralize the residual alkaline substances. If the neutralization is not complete, alkaline components will remain on the surface of aluminum plate, and problems such as uneven oxide film and local blackening will occur in subsequent anodic oxidation.

Second, the matters needing attention in washing and drying

Washing and drying are the keys to connect chemical cleaning with subsequent processes, and secondary pollution and water residue should be avoided.

Multi-pass water washing and subsection treatment: the subsection mode of "one hot water washing+two normal temperature washing" is adopted. Hot water washing (temperature 40-50℃) can quickly wash the residual degreasing agent and neutralizing solution on the surface, while normal temperature washing can further remove fine impurities. After each water washing, the aluminum plate should be completely drained to avoid carrying the solution from the previous procedure to the next one, which will cause cross-contamination.

Matching of drying temperature and speed: the drying temperature should be set at 80-120℃, and the drying time should be adjusted according to the thickness of aluminum plate (usually it takes 3-5 minutes for 0.3-1mm thick aluminum plate). If the temperature is too high or drying is too fast, the water on the surface of aluminum plate will evaporate quickly, which may lead to local residual water stains; If the temperature is too low or the drying is too slow, oxide layer will easily grow on the surface of aluminum plate, which will affect the drawing effect.

Anti-oxidation protection after drying: the dried aluminum plate should be immediately transferred to a sealed or inert gas protected environment, and the next process (wire drawing or embossing) should be carried out within 1 hour. If exposed to air for a long time, a new oxide film will quickly form on the surface of aluminum plate, and additional polishing is needed for subsequent wire drawing, which will increase the cost and affect the texture fineness.

Third, the quality standard of the substrate after inspection and pretreatment

After pretreatment, it is necessary to pass strict inspection to ensure that the surface of aluminum plate meets the requirements of subsequent processes and avoid unqualified products from flowing into the next ring.

Surface cleanliness inspection: wipe the surface of aluminum plate with a white dust-free cloth, and the cloth surface should be free of impurities such as oil stain, water stain and powder; When observed in the light, there are no obvious scratches, pits or oxidation spots on the surface to ensure the cleanliness reaches the standard.

Surface flatness inspection: put the aluminum plate on a flat detection platform, and measure the clearance between the aluminum plate and the platform with a feeler gauge, and the clearance shall be ≤ 0.1 mm/m.. If the flatness is not up to standard, uneven pattern depth will appear in subsequent embossing, and the texture will easily shift when drawing.

Confirmation of no corrosion damage: check the edge and surface of aluminum plate, and there is no depression, blackening or bottom exposure caused by local over-corrosion; Touch the surface by hand, without roughness or graininess, to ensure that the substrate is not damaged, and provide a good foundation for subsequent texture processing.