What are the metals that don't rust?
Metals such as aluminum, stainless steel, galvanized steel, copper alloys, titanium, platinum, and gold do not rust because they either do not contain iron or have a negligible amount of iron. As a result, these metals are widely used in the construction, chemical, marine, and decorative industries.
|Aluminum||Lightweight, cheap, ductile|
|Stainless Steel||Durable, glossy, tough|
|Titanium||Lightweight, extremely durable|
|Corten Steel||High tensile strength and corrosion resistance|
|Galvanized Steel||Zinc coating that provides good corrosion resistance|
|Copper||Excellent conductor and very ductile|
|Brass||Ideal for water applications|
|Bronze||Used for making decorative items, trophies, etc.|
|Platinum||Used for making jewelry|
|Silver||Used for making jewelry and decorative items|
|Gold||Inert metal, expensive, used for making jewelry|
This article provides a list of metals that do not rust and discusses the methods of preventing rusting in your workpieces.
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List of Metals That Don’t Rust
Rusting degrades a workpiece's performance and significantly reduces the equipment's lifetime.
The most effective way to overcome this problem is to use metals that don't rust.
However, selecting the right metal depends upon various other factors, such as strength, durability, machinability, etc.
Therefore, it is important to understand your requirements and select the best-suited metal for your application.
Aluminum is a non-magnetic metal that does not rust since it contains no iron, except in some alloys.
When exposed to water or moisture, aluminum reacts with oxygen, forming an aluminum-oxide film that acts as a thin corrosion-resistant protective layer, protecting the metal from further deterioration.
This anti-rust property can be used in a wide range of applications, such as kitchen utensils, car, and bike parts, etc.
Stainless steel with at least 11% chromium does not rust because chromium oxidizes faster than iron and forms a chrome oxide coating on the surface.
This oxide layer prevents rust formation and protects the underlying metal.
Apart from chromium, other elements, like nickel and molybdenum, can also be added to further improve the rust resistance of stainless steel.
When compared to aluminum, stainless steel provides better strength and durability, making it ideal for various applications including kitchen and building components that require good corrosion resistance and excellent durability, with an aesthetic appeal.
Despite its excellent resistance to rusting, stainless steel can rust under extreme exposure to chemicals, moisture, and abrasive conditions.
However, unlike aluminum, you cannot anodize stainless steel to improve its corrosion resistance but you can powder coat it.
Titanium is a lightweight, corrosion-resistant, and durable metal.
It forms an oxide coating layer over its surface when exposed to particular elements, such as chlorine, hot nitric acid, salt water, and extreme temperatures.
This oxide layer acts as a protective coating and prevents the corrosive elements from penetrating through, protecting the base titanium from corrosion.
Due to its excellent strength-to-weight ratio and ability to resist corrosion, titanium is widely used in aviation, military, chemical plants, and other engineering applications.
However, compared to other metals like steel or aluminum, it is more expensive and challenging to work with.
You can anodize titanium to achieve different colors and textures to add to its aesthetic value.
Corten or Weathering Steel
Weathering steel, also known as COR-TEN steel, is a steel alloy that provides excellent corrosion resistance and tensile strength.
It consists of up to 21% alloying elements such as chromium, copper, nickel, and phosphorus.
These elements combine to generate a protective coating, preventing corrosion over time. Moreover, weathering steel is comparatively less expensive than stainless steel.
Unlike other metals, corten steel undergoes rusting and forms a protective layer over its surface which then prevents the surface from further rusting.
As a result, COR-TEN steel is often utilized without paint for outdoor structural applications, like open-frame buildings, bridges, transmission poles, etc.
However, it is only suitable for applications where a rustic appearance is desirable.
Galvanized steel is a type of carbon steel that undergoes hot-dip galvanizing or electroplating to form a protective zinc layer over its surface.
As zinc reacts with oxygen at a comparatively faster rate than iron, it forms a zinc oxide layer on the surface of the workpiece.
The zinc oxide layer forms a barrier that prevents corrosive elements such as moisture and oxygen from reaching the base metal underneath, preventing the possibility of rusting.
Galvanized steel is used in manufacturing weather-resistant bolts, nuts, screws, balconies, bus stop benches, staircases, and ladders.
Copper, in its pure metallic form, is found in almost every household application such as wires, utensils, could, etc.
It has a lustrous brown appearance which makes it ideal for decorative applications.
Although copper does not rust, it is prone to corrosion and forms a bright green oxide layer, called patina.
This corrosive layer protects the metal from rusting but at the cost of its aesthetic appearance.
Copper alloys are widely used in applications that require resistance to atmospheric exposure, such as plumbing fittings, heat exchangers, industrial and chemical plant process equipment, etc.
Bronze is a copper alloy that does not rust.
Despite its excellent resistance to rusting, bronze can corrode when it comes in contact with chlorides.
This corrosion process is known as 'bronze disease and is an irreversible process that degrades the aesthetic appearance of bronze workpieces.
Due to its excellent resistance to rust, bronze is widely used in various decorative applications, door handles, and seawater applications like boats and ship fittings.
Brass is another copper alloy that oxidizes when it comes into contact with water, but it doesn't rust easily since it contains negligible amounts of iron.
The oxidized layer on brass is characterized by its hardened blackish, blue, or green patina.
It is highly suitable for plumbing fittings, hose couplings, valves, locks, hinges, etc.
Platinum is a precious metal that does not contain iron and, therefore, is immune to rusting.
It has good ductility with excellent resistance to rusting and other chemical changes such as discoloration.
As a result, it is comparatively more expensive than copper alloys and is widely used for making jewelry items.
Gold is the least reactive metal that is highly immune to rusting or corrosion.
It does not react with the moisture or oxygen present in the air, and hence, does not tarnish or rust even when exposed to harsh conditions.
Furthermore, gold has a lustrous appearance with excellent malleability, making it ideal for jewelry applications.
As pure gold is soft and subject to shape changes, alloys are frequently used to increase its strength.
It is one of the best conductors of heat and electricity and is therefore used in high-performance electrical applications such as computer processors.
However, all these advantages come at a high price, making gold one of the most costly metals on earth.
Silver is a pure metal that is immune to rusting. It has a lustrous and shiny appearance which makes it ideal for jewelry and other decorative applications.
Although silver does not actively react with oxygen to form an oxide layer, it can corrode when subjected to harsh conditions, forming a blackish layer of silver sulfide.
Due to its excellent finish and high price, silver is categorized as a precious metal along with gold and platinum.
What Causes Metals to Rust?
You must have faced the problem of rusting with your equipment and other metal workpieces and wondered what causes the metals to rust.
Rust is a reddish-brown oxide layer that forms on metal workpieces when they come in contact with air, moisture, salt, or other chemicals.
It commonly occurs in workpieces containing iron as its principal constituent.
This formation of oxide layer deteriorates the workpiece by eating away the metal from its surface.
Furthermore, the resulting rust is often scaly and loose, and it quickly breaks away, exposing more and more of the underlying material to the environment and continuing the rusting process.
As a result, it drastically reduces the lifespan of the workpiece, making it important to use rust prevention methods to protect the workpiece.
How to Prevent Metal from Rusting
The best technique to minimize rusting is to keep moisture and oxygen away from metals.
Although you cannot completely seal the workpiece, there are various techniques that you can use to minimize the risk of rusting the workpiece.
Selecting a Rust-resistant Alloy
The use of an appropriate alloy containing additional metals such as chromium, manganese, nickel, and others is a popular strategy for avoiding rust formation.
This technique is used to produce stainless steel, which provides excellent resistance to rusting.
Galvanizing The Workpiece
Galvanizing involves the coating of iron or steel workpieces with a thin layer of zinc, which prevents oxygen and moisture from reaching the base metal.
This is a low-cost and effective method for preventing rust. It is accomplished through electroplating or hot-dip galvanization.
However, the galvanized layer can be damaged due to harsh environmental factors such as acid rain or salt, leaving the base metal unprotected.
Furthermore, zinc is not completely immune to rusting, and can undergo corrosion at a slow rate.
Therefore, galvanizing is not a permanent solution, but it can provide excellent resistance to rust for a long period of time.
Powder Coating The Workpiece
Powder coating is the process of spraying powdered resin, followed by heating to cure it and produce a protective coating over the workpiece.
This layer keeps moisture out of the metal, avoiding rust, and improving the metal's surface finish.
Apart from that, it also improves the aesthetics of the workpiece by providing a wide range of colors to choose from.
You can also opt for a clear powder coating to retain the base metal's color.
Although it is not very expensive, the need for surface preparation, such as sandblasting the workpiece before powder coating to remove any pre-existing rust, can increase the overall cost of the process.
Painting the Metal Workpiece
Metal painting is a very simple and easy approach to avoid rust formation. This method is highly suggested for DIY projects, and you can paint with different colors.
You must choose the proper paint for your metal components in order for it to adhere to the metal.
It is usually preferable to use oil-based paint over water-based paint.
This is because the water content in a water-based paint can initiate rusting of metal, thereby damaging the workpiece instead of protecting it.
Oiling the Workpiece
In addition to lubricating the metal parts, oil coating keeps moisture from reaching the iron and prevents rust formation.
This is a really simple and easy option for your DIY project.
However, applying oil over the surface of the workpiece reduces friction, making it difficult to hold the components.
Apart from that, oil attracts dust, making the surface unpleasant and dirty.
Therefore, it is important to clean the workpiece regularly and re-oil it after every cleaning.
Rusting vs Corrosion: Is there a Difference?
|Reason||Air and moisture exposure||Chemicals or the air exposure|
|Material||Mainly occurs for iron and its alloys||Metals and non-metals are susceptible|
|Chemical composition||Formation of iron oxide layer||Formation of oxides, hydroxides, and sulfides|
|Color||Red-brown color||Different colors such as green, blue, etc.|
Rusting is a type of corrosion that occurs as a result of a chemical process that causes metal surfaces to develop a red-brown coating layer.
Metal will rust mostly when it is exposed to air and moisture.
Rusting typically occurs on workpieces made of iron and its alloys that readily form an iron oxide layer.
On the other hand, the degradation of materials due to chemical or other reactions is known as corrosion. It can happen when a substance is exposed to chemicals or air.
Corrosion is a chemical process that is applicable to a variety of materials such as wood, metals, plastics, skin, etc.
In this process, the elements that are present in the substance are transformed into the respective oxides, hydroxides, and sulfides.
Depending on the type of material, corrosion layers can have different colors such as green, blue, black, etc.
Rusting can damage metal parts and render them useless, leading to the failure of machines and equipment.
Therefore, it is important to select the right metal for your application based on your requirement.
For applications that involve outdoor operations, it is strongly recommended to either use metals that don't rust or protect the workpiece by rust-resistant methods.
Generally, aluminum, stainless steel, and titanium are preferable for industrial applications, while gold, silver, and platinum are ideal for making jewelry and some medical applications.
Copper and its alloys, such as brass and bronze, can be used in applications that are exposed to water or chemicals, such as plumbing fittings, heat exchangers, ships, etc.
Frequently Asked Questions (FAQ)
Can I paint over a rusted metal?
Yes, you can paint over rusted metal. However, you have to remove any loose rust and paint flakes using a soft brush or sandpaper before painting the surface.
Is anodized aluminum prone to rust?
No, anodized aluminum is not prone to rust. It involves submerging it in a chemical acid bath and flowing current through it. As a result, an anticorrosive coating is formed, which prevents rust.
Which is the least expensive metal that doesn't rust?
Aluminum is the least expensive metal that doesn't rust.