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Why does die-cast aluminum alloy oxidize and turn black?

2023/12/8 15:28:12 click:

In the actual cnc machining, manufacturers need to use corresponding materials to customize various aluminum parts according to the actual needs of customers. Industrial die-cast aluminum is a commonly used metal material for hardware machining. It has strong plasticity, light weight, beautiful surface, and natural silvery white color, and is favored by customers.

However, in actual application scenarios, the surface of die-cast aluminum alloy will become dark and dark, which greatly affects the aesthetics of the final part. However, under normal circumstances, the surface of die-cast aluminum alloys will not turn black on its own (if the surface of some aluminum materials turns dark after buying it, it may be a problem with the material. For example, the iron content in aluminum alloy materials exceeds the standard, and some use scrap aluminum to smelt. Some have excessive iron content and are cheap but have obviously insufficient mechanical properties). Under some special conditions, they will turn black for specific reasons:

A-Metal oxidation: Aluminum is a very active metal in nature and is prone to various oxidation reactions to form aluminum oxide. The oxide formed by black aluminum oxide usually covers the surface of the aluminum alloy, causing the surface of the die-cast aluminum alloy to appear black. Usually this film can form a certain degree of protection on the surface of the aluminum profile to prevent further oxidation of the metal. However, due to external factors, such as extrusion, friction, impact, etc., the oxide film will peel off, which will also cause the die-cast aluminum parts to be exposed to the air at a deeper level and become more black.

B-Surface pollution: In actual use, the surface of metal can easily accumulate dust, water vapor, oil and other external pollutants. At the same time, during handling and use, lactic acid, sweat stains, etc. in human skin will also cause certain pollution to the die-cast aluminum, which will accelerate the oxidation machining of the aluminum material, and the die-cast aluminum will oxidize and turn black more quickly.

C-Chemical reaction: Aluminum alloys are prone to chemical reactions when exposed to heavy moisture or even strong acid and alkali environments for a long time. These chemical reactions destroy the formation of the oxide film. In this case, the oxide film does not protect the aluminum material enough, and will also aggravate the blackening.

In addition to the above reasons, uneven surface density of the oxide film will also lead to uneven surface coloring and oxidation and blackening.

Blackening of die-cast aluminum will reduce the performance and lifespan of aluminum products, and will also make the aluminum surface no longer smooth and bright, affecting the overall quality of the product.


In order to prevent aluminum alloy from oxidizing and blackening, the following measures can be taken:

1-Surface treatment: Surface treatment of aluminum alloy surface, such as spraying, anodizing, etc. These treatments can form a protective film on the surface of the aluminum alloy, which will slow down the oxidation rate.

2-Regular cleaning: Clean the aluminum alloy surface regularly to remove dust, oil and other contaminants attached to the surface to prevent it from reacting with oxygen.

3-Surface coating: Apply a layer of paint or preservative on the surface of the aluminum alloy to establish a physical protective layer to prevent oxidation reactions.

4-Control temperature: Avoid exposing aluminum alloy to high temperature environments and try to reduce the speed of oxidation and blackening.

5-Avoid contact with corrosive media: Avoid contact of aluminum alloy with corrosive media such as strong acid and strong alkali to prevent oxidation and blackening caused by chemical reactions.

6-In daily use, do not touch aluminum profiles directly with your hands, but use protective gear such as gloves for protection.

7-Keep the die-cast aluminum surface dry and avoid being eroded by rain or moisture.

Through the above measures, the service life of the aluminum alloy can be better extended, the speed of oxidation and blackening can be slowed down, and the beautiful appearance of the aluminum alloy can be maintained.