About Anodizing & Aluminum

About Aluminum

The one yen coin is a readily recognizable item used by Japanese residents on a daily basis.
Official one yen coins produced by the Japan Mint are 100% pure aluminum. The alloy produced by adding various elements is called aluminum alloy.

Pure Aluminum = Only Aluminum, Aluminum Alloy = Aluminum + other elements such as Cl, Sl, Zn, Mg

Aluminum is actively used in a broad array of fields ranging from beverage cans to automobile parts. The addition of elements to pure aluminum produces the various characteristics needed by each of these fields.
Aluminum is steadily being adopted in cutting-edge fields through the addition of new functionality to its familiar conventional characteristics amidst modern-day demand for more diverse and advanced materials.

Characteristics of Aluminum

  • Lightweight

    Aluminum is 1/3 the specific gravity of iron. This lightness is being effectively utilized to boost the operating efficiency of sliding and rotating parts, reduce product weight, and enhance products in a variety of ways.

  • Strong

    Has great specific strength. Recently discovered high tensile alloy is gathering attention as a material for aircraft and large-scale structures.

  • Corrosion Resistant

    Reacts with air, naturally generating a dense, stable oxide film that protects the surface from corrosion.

  • Good
    Workability

    Suitable for plastic working. Easily workable into thin, complex shapes that can be additionally processed with relative ease.

  • Good
    Electrical Conductivity

    Only 60% the electrical conductivity of copper but 1/3 the specific density, so can pass twice the current as the same weight of copper. Increasing demand in the electronics field.

  • Not
    Magnetic

    Nonmagnetic material unaffected by magnetic fields. Utilized for a wide array of applications including medical electronic devices, mechatronics equipment and linear motor cars.

  • GoodThermal Conductivity

    Approximately 1/3 the thermal conductivity of iron. Good thermal conductivity also means rapid cooling, a property facilitating use in various areas such as air conditioners, engine parts, heat exchangers, radiating fins, heat sinks.

  • Resistant to Low Temperatures

    Characterized by high toughness and resistance to brittle fractures even in extremely low temperatures. These characteristics are attracting attention in cutting-edge fields such as aerospace development, biotechnology, and cryogenically cooled superconductors.

  • Reflects
    Light and Heat

    Well polished aluminum reflects infra-red radiation, electromagnetic waves, and a full range of heat rays. Widely used in electronics after mirror finishing is used to enhance its reflective properties.

  • Nonpoisonous

    Harmless, odorless and hygienic. Doesn’t damage health or environment like heavy metals. Utilized for these characteristics in fields such as food, pharmaceutical packaging, beverage cans, and medical devices.

  • Easy to Cast

    Characteristics such as a low melting point, generation of protective oxide film on the surface even when melted, minimal gas absorption, and good fluidity make it ideal for thin and complexly shaped castings.

  • Easy to Join

    Can easily gain a highly reliable joint via welding, brazing, soldering, electric resistance welding, riveted joint, adhesion and various other methods. Efficiently streamlines design and application processes.

  • GoodVacuum Properties

    The metal itself has an extremely low gas evolution rate when used in vacuum equipment, and exhibits superb vacuum-reaching performance compared to other materials.

  • Easily
    Recycled

    Can be easily melted and recycled due to its low melting point. The energy needed to create secondary metal is a mere 3% of that needed to make primary metal. It can be regarded as an economic material.

  • Aesthetically Pleasing

    Aesthetically pleasing even as bare metal, aluminum can be colorfully coated via surface treatment, making it ideal for fields demanding a high level of designability.

Types, Characteristics, Application of Aluminum

There are several types of aluminum alloy with different characteristics and for a range of applications.

JIS Standard Alloy Type Type and Application
A1000,etc Pure Aluminum Has poor strength. Good workability, corrosion resistance and weldability. Excellent electrical and thermal conductivity. Applications include light reflectors, ornaments, containers, and electric appliances.
A2000,etc Al-Cu Alloys
Aluminum and Copper
Good strength and machinability. Ideal for aircraft, transportation equipment and structural material, but not suitable for highly corrosive environments.
A3000,etc Al-Mn Alloys
Aluminum and Manganese
Corrosion resistance maintained with added strength. Slightly poorer workability than pure aluminum. Has a wide range of applications including utensils, construction materials, and containers.
A4000,etc Al-Si Alloys
Aluminum and Silicon
Used for forged pistons, building panels, and welding wire. Also used as a brazing material due to its low melting point.
A5000,etc Al-Mg Alloys
Aluminum and Magnesium
Grinding low magnesium materials produces a highly lustrous finish suitable for ornaments. High magnesium materials are used for can lids and construction materials. Also used for ship building due to high resistance to salt water and contaminants.
A6000,etc Al-Mg-Si Alloys
Aluminum, Magnesium,
Silicon
6061 - an alloy with a minute amount of added cooper – has good corrosion resistance and is used for various structural materials. The slightly weaker 6063 has good extrudability and is used in a diverse range of construction materials.
A7000,etc Al-Zn-Mg Alloys
Aluminum, zinc,
Magnesium
Also known as Extra Super Duralumin A7075, it is the strongest of all aluminum alloys. Used for aircraft and sporting goods.
JIS Standard Alloy Type
Type and Application
A1000,etc Pure Aluminum
Has poor strength. Good workability, corrosion resistance and weldability. Excellent electrical and thermal conductivity. Applications include light reflectors, ornaments, containers, and electric appliances.
A2000,etc Al-Cu Alloys
Aluminum and Copper
Good strength and machinability. Ideal for aircraft, transportation equipment and structural material, but not suitable for highly corrosive environments.
A3000,etc Al-Mn Alloys
Aluminum and Manganese
Corrosion resistance maintained with added strength. Slightly poorer workability than pure aluminum. Has a wide range of applications including utensils, construction materials, and containers.
A4000,etc Al-Si Alloys
Aluminum and Silicon
Used for forged pistons, building panels, and welding wire. Also used as a brazing material due to its low melting point.
A5000,etc Al-Mg Alloys
Aluminum and Magnesium
Grinding low magnesium materials produces a highly lustrous finish suitable for ornaments. High magnesium materials are used for can lids and construction materials. Also used for ship building due to high resistance to salt water and contaminants.
A6000,etc Al-Mg-Si Alloys
Aluminum, Magnesium,
Silicon
6061 - an alloy with a minute amount of added cooper – has good corrosion resistance and is used for various structural materials. The slightly weaker 6063 has good extrudability and is used in a diverse range of construction materials.
A7000,etc Al-Zn-Mg Alloys
Aluminum, zinc,
Magnesium
Also known as Extra Super Duralumin A7075, it is the strongest of all aluminum alloys. Used for aircraft and sporting goods.

Aluminum alloy is divided into two main categories depending on the varied requirements and applications of the final product.

Aluminum Alloy、Aluminum Alloy for Wrought Products:Used in sheets, foil, pipes, rods, wires, rivets bars, and profiles. This alloy has excellent extending workability and includes forged products. Aluminum Alloy for Casting:Alloy with excellent casting properties used for sand casts, shell molds, metal molds, die casting, and various other casting applications.

  • Non-Heat Treatable Alloy・・・・・・
  • Alloy that can be strengthened mainly through cold working (rolling, etc.) and the addition of elements.
  • Heat-Treatable Alloy・・・・・・
  • Extremely strong alloy produced by solutionizing (quenching) and thermal treatment such as aging (tempering: additional elements diffuse through the metal, enhancing the material’s strength, hardness, and other properties over time).
    After thermal treatment, heat-treatable alloys may be cold worked to further enhance strength. Even non-heat-treatable alloys are subject to conventional heat treatments such as annealing and stabilizing treatment to eliminate machining deformations. Anodizing is a treatment applied to this processed aluminum.

Comparison with Assorted Metals

A comparison of aluminum with the commonly used metals iron and copper.

Element Aluminum (Al) Iron (Fe) Copper (Cu)
Lightness Specific Gravity 2.7 Specific Gravity 7.9 Specific Gravity 4.5
Advantages Low elasticity, light, soft Rigid, strong, heavy, some elasticity 1.Good thermal conductivity
2.Resistant to low temperatures
3.Good electrical conductivity
4.Nonmagnetic material
5.Antibacterial properties
Melting Point(℃) 660.4 1535 1084.5
Density/Hardness 2700 kg/m3, 2.75 7874 kg/m3, 4.0 8920 kg/m3, 3.0
Thermal Conductivity 237 W/(m*K) 80.2 W/(m*K) 401 W/(m*K)
Electrical Conductivity 37.7×/m × 106S/m 9.93×/m × 106S/m 59.6×/m × 106S/m
Corrosion Resistance Rusts easily (excluding stainless steel) Average rust resistance
(displays tarnish, copper rust)
Doesn’t rust easily
Nonmagnetic Unaffected Affected Unaffected
Workability Low elasticity, so cracks easily when bent. Soft and easy to cut. Reasonable elasticity, so easy to bend if thin. High density makes it difficult to cut. Takes 2 to 3 times longer than aluminum and brass. Elasticity makes it ideal for bending. Easy to cut.
Typical Uses 1 yen coin
Aluminum wheels
Aluminum cans
Pots, kettles
Fittings (windows sashes, doors, etc.)
Railroad vehicles (chassis, lifting eye, etc.)
Automobiles (Honda NSX, Prince R380, etc.)
Motorcycle frames
Reducer for thermit welding
Steel products
Cans
Industrial products
Household goods
Ornaments, etc.
Electrical wires and wiring for circuit boards
Air conditioners
Refrigerators
Interior finishing materials
Freezing equipment
Material for electrical wires and cables
Socks, sock liners
Carpets, mats, etc.
Element Aluminum (Al)
Lightness Specific Gravity 2.7
Advantages Low elasticity, light, soft
Melting Point(℃) 660.4
Density/Hardness 2700 kg/m3, 2.75
Thermal Conductivity 237 W/(m*K)
Electrical Conductivity 37.7×/m × 106S/m
Corrosion Resistance Rusts easily (excluding stainless steel)
Nonmagnetic Unaffected
Workability Low elasticity, so cracks easily when bent. Soft and easy to cut.
Typical Uses 1 yen coin
Aluminum wheels
Aluminum cans
Pots, kettles
Fittings (windows sashes, doors, etc.)
Railroad vehicles (chassis, lifting eye, etc.)
Automobiles (Honda NSX, Prince R380, etc.)
Motorcycle frames
Reducer for thermit welding
Element Iron (Fe)
Lightness Specific Gravity 7.9
Advantages Rigid, strong, heavy, some elasticity
Melting Point(℃) 1535
Density/Hardness 7874 kg/m3, 4.0
Thermal Conductivity 80.2 W/(m*K)
Electrical Conductivity 9.93×/m × 106S/m
Corrosion Resistance Average rust resistance
(displays tarnish, copper rust)
Nonmagnetic Affected
Workability Reasonable elasticity, so easy to bend if thin. High density makes it difficult to cut. Takes 2 to 3 times longer than aluminum and brass.
Typical Uses Steel products
Cans
Industrial products
Household goods
Ornaments, etc.
Element Copper (Cu)
Lightness Specific Gravity 4.5
Advantages 1.Good thermal conductivity
2.Resistant to low temperatures
3.Good electrical conductivity
4.Nonmagnetic material
5.Antibacterial properties
Melting Point(℃) 1084.5
Density/Hardness 8920 kg/m3, 3.0
Thermal Conductivity 401 W/(m*K)
Electrical Conductivity 59.6×/m × 106S/m
Corrosion Resistance Doesn’t rust easily
Nonmagnetic Unaffected
Workability Elasticity makes it ideal for bending. Easy to cut.
Typical Uses Electrical wires and wiring for circuit boards
Air conditioners
Refrigerators
Interior finishing materials
Freezing equipment
Material for electrical wires and cables
Socks, sock liners
Carpets, mats, etc.

Reason for Surface Treatment

We are surrounded by a multitude of metal products in our everyday lives, the majority of which have been surface treated in one way or another to compensate for the various disadvantages of metal.

Advantages of Metal
  • Wear

    Metal gradually wears when rubbed together causing unstable operation in the form of rattling and other abnormal phenomena. Even micro vibrations will cause wear.

  • Easily Corrodes

    Corrosion caused by the surrounding environment is called rust. It is visually unpleasing and will adversely affect properties such as strength and durability.

  • No Color Variation

    The color of metals such as gold, silver, copper, iron, tin, and lead is fixed, so much so that the name of each metal has represented a color since ancient times.

That’s why…Surface treatment is applied to make up for these disadvantages.

The use of metal will inevitably lead to corrosion. Disadvantages such as wear, lack of color and no lubrication cannot be avoided. Humans have sought and will continue to seek out new treatment techniques to overcome these inherent disadvantages.

Familiar Everyday Aluminum Products that have been Surface Treated

A quick look at everyday goods will reveal a variety of characteristic surface treatments and coatings. You can see that surface treatment is implemented to compensate for the weak points of metal.

Frying Pans
Corrosion Resistance and Heat Resistance

The exterior of a frying pan made from aluminum alloy is treated with a highly heat resistant baked coating.

  • Protects the aluminum from the stove’s flame, electromagnetic cookers, etc.
  • Prevents corrosion
  • Aesthetically pleasing as kitchenware
Prevents Burning

The inside of the frying pan is coated with fluororesin.

  • Strong, resistant to strong alkali environments
  • Repels water and oil
  • Won’t stick even when burnt
Corrosion Resistance

Each manufacturer applies a different coating to the bottom section of the frying pan in contact with the stove’s flame.
It may be the same as the side plate, anodized, or ground down to bare aluminum to maximize heat conduction.

Beverage Cans
Corrosion Resistance

Carbonated drink cans have a resin coating.

  • Prevents the acid in orange juice etc. from corroding the aluminum
  • Enhances recyclability
Audio
Aesthetic Beauty

The photo is Bang & Olufsen’s BeoSound 1.
The vibrant color generated by anodizing (anodizing) the aluminum speaker grill produces an unmatched stylish finish. Coloring metals is an important goal of surface treatment.

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