How about the corrosion resistance of aluminum

What is the corrosion resistance of metals?

The corrosion resistance of metal products refers to the property that metal materials are not prone to corrosion or oxidation reactions when they come into contact with chemical substances or the environment. Corrosion refers to the gradual loss of its original properties and forms of metals under certain environmental conditions due to the action of oxygen, water, acid, alkali or other chemical substances.

The corrosion resistance of metal products is an important performance index, especially for metal products used in harsh environments, such as marine equipment, automotive parts, building structures, piping systems, etc. The quality of corrosion resistance directly affects the service life and safety of the product.

Our common metals are iron, copper, aluminum, etc. In terms of corrosion resistance of metals, we compare them;

How about the corrosion resistance of aluminum？

• Iron: The corrosion resistance of pure iron (Fe) is relatively poor, it is easily oxidized by the action of oxygen and water, and produces rust (iron oxide), which leads to corrosion and damage of the metal surface. Rust not only affects the appearance of metal, but also reduces the strength and durability of iron.
• Copper: In some environments, copper can form a layer of patina (basic copper carbonate), forming a protective film against continued corrosion.
• Aluminum: In the presence of oxygen, aluminum will form a layer of aluminum oxide film by itself to protect the base metal.

How to Improve the Corrosion Resistance of Aluminum

Alloying

Under normal circumstances, the corrosion resistance of aluminum alloy is higher than that of pure aluminum.

Aluminum alloy (Aluminum Alloy) generally has good corrosion resistance. This is because a layer of aluminum oxide (Al2O3) film is naturally formed on the surface of the aluminum alloy. This oxide film has a certain degree of sealing and stability, and can effectively prevent further corrosion reactions. This characteristic makes aluminum alloys exhibit good corrosion resistance in many environments.

However, the corrosion resistance of aluminum alloys is also affected by some factors, including alloy composition, quality of oxide film, and environmental conditions. The following are some factors that affect the corrosion resistance of aluminum alloys:

Alloy composition: Different types of aluminum alloys contain different alloying elements, and the addition of these elements will affect the corrosion resistance of aluminum alloys. For example, the addition of elements such as copper and zinc may reduce the corrosion resistance of aluminum alloys, while the addition of elements such as magnesium and manganese may improve its corrosion resistance.

Oxide film quality: The quality of oxide film on the surface of aluminum alloy directly affects its corrosion resistance. A more uniform, dense and stable oxide film can better protect the base metal.

Environmental conditions: The corrosion resistance of aluminum alloys may vary under different environmental conditions. For example, aluminum alloys may have relatively poor corrosion resistance in acidic environments.

Surface treatment

Surface treatment is an effective way to improve the corrosion resistance of aluminum alloys. The following are two common surface treatment methods for aluminum alloys:

Anodizing

Anodizing is a common surface treatment used to enhance the corrosion resistance, hardness and surface aesthetics of aluminum alloys. The process involves using an aluminum alloy product as an anode, and forming an oxide film on its surface through electrolysis. This oxide film is usually aluminum oxide (Al2O3), which has good sealing and corrosion resistance.

Aluminum alloy anodizing steps:

• Cleaning: First, aluminum alloy products are cleaned through steps such as degreasing, dust removal and pickling to ensure that the surface is clean for good results in the oxidation process.
• Pretreatment: Next, the aluminum alloy article is pretreated by immersing it in a chemical solution, usually an alkaline solution, to remove oxides and impurities from the surface.
• Anodizing: In an electrolytic cell, the aluminum alloy product is used as an anode and immersed in an electrolyte containing sulfuric acid, aluminum sulfate or aluminum potassium sulfate. By applying a direct current, the surface of the aluminum alloy starts to undergo an oxidation reaction to form an aluminum oxide film.
• Oxide film formation: During the electrolysis process, the aluminum oxide film will gradually thicken to form a uniform and dense oxide film layer. The thickness of the oxide film can be adjusted by controlling the electrolysis time and current density to meet the needs of different applications.
• Sealing: The formed oxide film is usually porous, and in order to increase the sealing and corrosion resistance of the oxide film, it can be sealed. Common hole sealing methods include hot water sealing, nickel passivation sealing, etc.
• Dyeing (optional): If the color of the oxide film needs to be changed, dyeing techniques can be used. By adding different pigments or colorants to the oxide film, the oxide film can show different colors.

Powder coating

Powder coating is a surface treatment technique used to impart a corrosion-resistant, aesthetically pleasing coating to aluminum alloy products. This method is suitable for occasions where it is necessary to increase the surface hardness, wear resistance, corrosion resistance and decorative properties of aluminum alloy products. The sprayed paint is usually made of a mixture of aluminum alloy powder and resin, and different colors and textures can be selected to meet different design requirements.

The following are the basic steps of aluminum alloy powder coating treatment:

• Surface pretreatment: Before spraying treatment, it is necessary to ensure that the aluminum alloy surface is clean and smooth. Surface pretreatment steps such as degreasing, dust removal and pickling are usually carried out to remove grease, impurities and oxides from the surface to ensure that the sprayed coating adheres well.
• Spraying preparation: Components such as aluminum alloy powder and resin are mixed and evenly distributed in special spraying equipment. Usually, a spray gun is used to uniformly spray the mixture on the surface of the aluminum alloy product.
• Spraying treatment: place the aluminum alloy product in the spray booth, and use a spray gun to evenly spray the mixture on the surface of the aluminum alloy. The thickness of spraying can be adjusted as needed to meet different application requirements.
• Curing: The sprayed coating needs to go through a curing process, usually by heating at a specific temperature. The curing process makes the coating strong, wear-resistant and corrosion-resistant.
• Cooling and inspection: After solidification, aluminum alloy products need to be cooled, and quality inspection is carried out to ensure that the quality of the coating meets the requirements.

Summarize

Through the explanation of the above article, we know that aluminum alloy has strong corrosion resistance, especially 5052 aluminum alloy and 6061 aluminum alloy, which are often used in shipbuilding and other fields, and are called marine-grade aluminum plates;

If there is a higher requirement for the corrosion resistance of aluminum alloy, surface treatment processes such as anodizing or powder coating can be carried out to improve the corrosion resistance of aluminum alloy.