Does Aluminum Rust Or Corrode? Corrosion Resistance of Aluminium and Aluminum Alloys

Sat, 09 Sep 2023 23:19:59 +0800

Does Aluminum Rust or Corrode?

Aluminum does not rust or corrode under most conditions of use and has high corrosion resistance. When the surface of aluminum is exposed to the atmosphere, it will immediately form a thin invisible oxide film (Al2O3·3H2O) to prevent further oxidation of the metal. This self-protection feature makes aluminum highly resistant to corrosion. Unless exposed to certain substances or conditions that destroy the protective oxide coating, the metal still has adequate corrosion protection. Even in industrial environments that often corrode other metals, aluminum has high weather resistance.

In this article, “rust” refers to “corrode”, because rust is an iron oxide, which only occurs in iron and other iron-containing metals.

Aluminium Corrosion Resistance

Alkali is one of the few substances that attack oxide films and therefore cause aluminum corrosion. Although metals can be safely used in the presence of certain weak bases with the help of corrosion inhibitors, direct contact with alkaline substances should generally be avoided.

The corrosion resistance of some aluminum alloys is not as good as others, especially some high-strength aluminum alloys. However, by covering the exposed surface with a thin layer of pure aluminum or an alloy with higher corrosion resistance, such alloys can be effectively protected from most corrosion effects.

Attention should also be mentioned. In the presence of electrolyte, avoid direct contact with certain other metals; otherwise, galvanic corrosion of aluminum may occur near the contact area. If other metals must be fixed to aluminum, it is recommended to use bituminous paint or insulating tape.

Corrosion Resistance of Aluminium and Aluminum Alloys

1xxx series, unalloyed (pure) aluminium, purity ≥ 99.00%, have excellent corrosion resistance.

2xxx series, Copper is the main alloying element, these alloys do not have good corrosion resistance like most aluminum alloys, and under certain conditions, they may be subject to intergranular corrosion. Therefore, these alloys are usually coated with 6xxx series high-purity alloys or magnesium-silicon alloys in sheet form to provide electrical protection for the core material, thereby greatly improving corrosion resistance.

3xxx series, Manganese is the main alloying element in this type of alloy. They have high corrosion resistance. The corrosion resistance in the atmosphere is similar to that of industrial pure aluminum, the same as pure aluminum in seawater. Better than pure aluminum in dilute hydrochloric acid; No such alloys have a tendency to stress corrosion cracking.

4xxx series, silicon is the main element, but silicon has the least influence on the corrosion resistance of these alloys. This is due to the fact that silicon particles are highly polarized, resulting in low corrosion current density.

5xxx series, Magnesium is the main alloying element, have pitting corrosion, intergranular corrosion, stress corrosion and denudation tendency. As the magnesium content increases, the tendency of pitting corrosion increases; as the amount of cold working deformation increases, the susceptibility to stress corrosion and denudation increases.

6xxx series, contains approximate proportions of silicon and magnesium to form magnesium silicides, which makes them heat-treatable and has good corrosion resistance. The main one in this series is 6061 aluminum alloy.

Corrosion of Aluminum and Aluminum Alloys

Pitting Corrosion: For aluminum, the most common pitting corrosion is halide ion, and chloride ion (Cl-) is the most common in use, such as NaCl (saltwater, the main source is seawater).

Galvanic Corrosion: Aluminum and its alloys will fail due to galvanic corrosion, so avoid contact of aluminum with more cathode metal. If such contact is required, protective measures should be taken to minimize sacrificial corrosion of aluminum. In many environments, aluminum can come into contact with chromium or stainless steel, only slightly accelerating corrosion.

Intergranular Corrosion is selective corrosion of grain boundaries or close adjacent areas, but no obvious corrosion to the grains themselves. Intergranular corrosion is caused by the potential difference between the grain boundary region and adjacent grains.

Stress-Corrosion Cracking (SCC): SCC in aluminum alloys is usually intergranular. Only aluminum alloys containing large amounts of soluble alloying elements (mainly copper, magnesium, silicon and zinc) are susceptible to SCC. For most commercial alloys, tempering properties that are highly resistant to SCC in most environments have been developed.

Does Aluminum Rust in Water

Aluminum hardly rusts in water, because aluminum will form a thin aluminum oxide film on the surface in the air to prevent further rust. When aluminum is placed in water, this passivation film isolates the water from the internal metal aluminum, so aluminum will not rust in water.

Does Aluminum Rust in Saltwater

Aluminum can rust in saltwater because the saltwater contains a large amount of chloride ions (Cl-), which can destroy the oxide film on the aluminum surface, causing pitting and intergranular corrosion.

Aluminum 6063-T6 T5; AA 6063 Aluminum Alloy Properties

Sat, 09 Sep 2023 22:38:23 +0800

Aluminum 6063-T6, T5 (AA6063 Alloy)

AA 6063 aluminum is one of the Al-Mg-Si series aluminum alloys, containing about 1% Mg2Si. It has excellent extrudability, moderate strength, good weldability, corrosion resistance and resistance to stress corrosion cracking (SCC), widely used in extruded architectural profiles and decorative finishes. The common temper conditions of AA6063 mainly include: aluminum 6063-T5, 6063-T6, etc.

Alloy 6060, an extruded aluminum popular in Europe, has the same purpose and very similar mechanical properties as AA6063 (slightly weaker than aluminum grade 6063, and even more extrudable).

Compared to Al-6061 and 6082 (popular alloy in Europe), Al-6063 is used in construction applications as a lower strength and slightly lower cost alloy. This alloy is ideal for surface treatments such as anodizing. Extrusions of alloy 6063 are generally considered to provide a better anodized appearance than 6061, but they are not as strong.

AA 6063 Aluminum Properties

The following tables summarize AA 6063 aluminum properties including chemical composition, physical and mechanical properties, etc.

Chemical Composition

The chemical composition of 6063 aluminum alloy is given in the data sheet below.

6063 Aluminum Alloy Physical Properties

Aluminum 6063-T5 T6 physical properties are listed in the data sheet below, including the aluminum density, melting point, coefficient of thermal expansion, Young’s modulus, thermal conductivity, specific heat, electrical conductivity, and electrical resistivity, etc.

10^-6·K^-1 = 10^-6/K = 1 μm/m·^oC

1 Ω·mm²/m = 1 μΩ·m

1 g/cm³ = 1 kg/dm³ = 1000 kg/^m3

1 GPa = 1 kN/mm²

1 MPa = 1 N/mm²

MS/m = 0,58% IACS

1 cal/(g.C) = 1 Btu/(lb⋅F)

6063 Aluminum Mechanical Properties

Aluminum 6063 mechanical properties are listed in the table below, including tensile strength, yield strength, elongation, hardness, etc.

ASTM B210/B210M

ASTM B210/B210M: Standard Specification for Aluminum and Aluminum-Alloy Drawn Seamless Tubes

Note:

(a) Material in the T42 or T62 tempers is not available from the material producers.

(b) The elongation in 50 mm (2 in.) is suitable for full-section test tubes, plate specimens, tubes with flat walls, and similar bending specimens with curved walls up to a maximum wall thickness of 12.50 mm. Elongation in 5D (5.65√A), D and So are the diameter and cross-sectional area of the specimen, respectively, and are suitable for circular specimens with a wall thickness exceeding 6.30 mm.

ASTM B221

Standard Specification for Aluminum and Aluminium-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes

ASTM B241/B241M

ASTM B241/B241M: Aluminium and Aluminum-Alloy Seamless Pipe and Seamless Extruded Tube

ASTM B429/B429M

ASTM B429/B429M: Aluminium-Alloy Extruded Structural Pipe and Tube

Applications of 6063 Aluminum Alloy

Typical uses of AA 6063 aluminum alloy include: furniture, doors, window frames, architectural profiles, decorative finishes, plumbing, railings, truck and trailer floors, electrical and electronic parts, highway signs, hospital and medical equipment, kitchen equipment, radiators; Extrusions in trains, cars and airplanes.

6063 Aluminum Alloy Equivalent Material

AA 6063 aluminum alloy equivalent material is listed in the table below including US ASTM, SAE; European EN, ISO, Australian AS/NZS, Japanese JIS and Chinese GB standard.

Note:

ASTM B210: Aluminum and Aluminum-Alloy Drawn Seamless Tubes

ASTM B221: Extruded Bars, Rods, Wire, Profiles and Tubes

ASTM B241/B241M: Seamless Pipe and Seamless Extruded Tube

ASTM B429/B429M: Aluminum-Alloy Extruded Structural Pipe and Tube

SAE AMS 4156: Aluminum Alloy, Extrusions 0.68Mg-0.40Si (6063-T6 Aluminium) Solution and Precipitation Heat Treated

AMS-QQ-A-200/9: 6063 Aluminum Alloy, Bar, Rod, Shapes, Tube, and Wire, Extruded

Does Aluminum Rust Or Corrode? Aluminium Corrosion Resistance

Fri, 01 Sep 2023 15:31:02 +0800

Does Aluminum Rust or Corrode?

In this article, “rust” refers to “corrode”, because rust is an iron oxide, which only occurs in iron and other iron-containing metals.

Aluminium Corrosion Resistance

Corrosion Resistance of Aluminium and Aluminum Alloys

1xxx series, unalloyed (pure) aluminium, purity ≥ 99.00%, have excellent corrosion resistance.

Corrosion of Aluminum and Aluminum Alloys

Pitting Corrosion: For aluminum, the most common pitting corrosion is halide ion, and chloride ion (Cl-) is the most common in use, such as NaCl (saltwater, the main source is seawater).

Does Aluminum Rust in Water

Does Aluminum Rust in Saltwater

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