Summarize the causes of plum blossom spots and snow spots on the surface of aluminum profiles
The density of aluminum profiles is only 2.7g/cm3, which is about one-third of the density of steel, copper, or brass (7.83g/cm3, 8.93g/cm3, respectively). Under most environmental conditions, including air, water (or salt water), petrochemicals, and many chemical systems, aluminum can exhibit excellent corrosion resistance. Summarize the causes of plum blossom spots and snow spots on the surface of aluminum profiles.
a) The relationship between the content of Zn, the size of the cross-sectional area, and the degree of air cooling. In mid June, alloy ingots with high Zn content (0.027%~0.047%) produced profiles that are prone to snow spots were placed in winter. These alloy ingots were used to extrude industrial aluminum profiles of the same specification in production, and after alkaline corrosion surface treatment, no snow spots appeared.
b) The size of snow spots varies, with the larger ones having a diameter of 5.2mm. Some industrial aluminum profiles have dense snow spots on their surfaces, with up to 90 spots per square centimeter. The distribution of snow spots on industrial aluminum profiles with a length of 6m is irregular: some have snow spots on one end, while others do not; Some have this side, while the other side does not; There are also several faces available.
conclusion
(1) Snow spots on industrial aluminum profiles produced in summer often appear on extruded profiles such as hollow profiles with large cross-sectional areas and curtain walls with thick wall thicknesses.
(2) When the Zn content of extruded aluminum profiles is between 0.02% and 0.045%, the appearance of snow spots on the surface is related to the speed of air cooling quenching.
(3) Aluminum profiles with Zn content greater than 0.02% are prone to snow spots on the surface of industrial aluminum profiles produced in summer. Aluminum profiles with a Zn content below 0.045% are generally less prone to snow spots during winter production.
(4) The snowflake like spots on the surface of industrial aluminum profiles are not corrosion-resistant. The product of CL ion reaction in the water washing tank or the product of reaction with dilute sulfuric acid – strictly control the filtration of tap water or well water entering the factory, reverse flow of water washing, ion testing in water, and other factors can be ruled out.
The above is a summary of the reasons for the formation of plum blossom spots and snow spots on the surface of aluminum profiles, hoping to be helpful to you. In addition, the machinability of aluminum profiles is excellent. In various deformed aluminum alloys and cast aluminum alloys, as well as in the various states in which these alloys are produced, there are significant changes in machining characteristics, which require special machine tools or techniques. If you have any other questions, feel free to call us for consultation. Our editor is dedicated to serving you.
