What Is Corrosion-Resistant Metals? Definition, Types, Applications

In the demanding realm of industrial manufacturing, the selection of the right materials is pivotal. Corrosion-resistant metals, for instance, have been a cornerstone for countless industries aiming to maintain the quality and longevity of their products. 

At Worthy Hardware, our specialization in cnc machining parts and sheet metal fabrication parts has made us witness the unmatched importance of these metals.Dive with us as we explore the intricacies of corrosion-resistant metals, their types, applications, and their undeniable significance in modern manufacturing.

What is Corrosion-Resistant Metals?

Corrosion-resistant metals are materials uniquely designed or inherently capable of resisting the harmful effects of oxidation and other chemical reactions that can degrade and wear them down. 

The battle against corrosion is as old as the usage of metals themselves. With advancements in technology and metallurgy, certain metals like titanium resistance and 420 stainless steel corrosion resistance have emerged as champions in this battle, showing remarkable resilience against environmental factors that typically cause decay.

Types of Corrosion-Resistant Metals

Stainless Steel

This is a ubiquitous alloy mainly composed of iron, carbon, and chromium. The chromium content, typically between 10-20%, gives it its anti-corrosive properties. There are several categories of stainless steel, each with distinct properties:

Austenitic Stainless Steel: Predominantly made of 18% chromium and 8% nickel, this type is known for its superior corrosion resistance. The 300-series, like 304 and 316, are examples of this category, with the latter being highly corrosion-resistant.

Ferritic Stainless Steel: Containing 12-18% chromium and having a body-centered cubic grain structure, they are magnetic and known for good corrosion resistance and formability. Common grades include 409 and 430.

Martensitic Stainless Steel: This steel contains around 12-14% chromium and is known for its high strength and moderate corrosion resistance. Examples include the 410 and 420 series.

Duplex Stainless Steel: It is a mix of austenite and ferrite structures, giving it both superior strength and excellent corrosion resistance compared to the standard austenitic steels. Typically, it contains 19-28% chromium, 5-7% nickel, and up to 4.5% molybdenum. The increased chromium and molybdenum content provide significant resistance to corrosive substances. Popular grades in this category include 2205 and 2507.

Aluminum

With its intrinsic ability to form a protective oxide layer when exposed to air, aluminum offers excellent corrosion resistance. Various grades provide differential resistance levels:

1xxx Series: This pure aluminum series boasts excellent resistance and is commonly used in electrical applications due to its high conductivity.

3xxx Series: With manganese as the primary alloying element, this series offers a balance of corrosion resistance and mechanical strength.

5xxx Series: Magnesium is a significant component here, enhancing the alloy’s resilience against corrosion, especially in marine environments.

Brass

Brass is an alloy primarily made up of copper and zinc. Its corrosion resistance is commendable, especially against dezincification, which makes it an optimal choice for applications where water exposure is frequent. 

The zinc content can vary, which impacts its mechanical properties and color – from yellow to red. Popular grades in this category include C36000.

Copper

Copper is a pure element with a distinctive reddish-brown hue. It’s renowned for its corrosion resistance, particularly atmospheric corrosion. Over time, when exposed to the elements, copper forms a green patina called verdigris. This patina is not only protective but also sought after for its aesthetic appeal, especially in architectural designs

Bronze

Bronze is an alloy mainly composed of copper, typically with tin as its primary additional element, but it can also contain other elements such as aluminum, manganese, or phosphorus. The corrosion resistance of bronze is notable, especially against seawater corrosion.

Titanium

Titanium is a lightweight, strong metal known for its outstanding corrosion resistance. The oxide film that naturally forms on its surface when exposed to air acts as a protective barrier against corrosion. This barrier is particularly resistant to erosion in seawater, making titanium an excellent choice for marine and underwater applications.

Superalloys

Superalloys, as the name suggests, are a group of alloys designed to have superior mechanical strength and corrosion resistance at high temperatures. They are mainly composed of nickel, cobalt, and iron, with additional elements like chromium, molybdenum, and tungsten. 

Galvanized Steel

Galvanized steel is regular steel coated with a layer of zinc to protect it from corrosion. The zinc serves as a sacrificial anode, corroding before the steel does, thereby prolonging the life of the steel. 

This process of adding a zinc layer, known as galvanization, greatly enhances the corrosion resistance of the base steel. 

Corten or Weathering Steel

Corten, commonly known as weathering steel, is a group of steel alloys that were developed to eliminate the need for painting. Instead, the steel forms a stable rust-like appearance when exposed to the elements. 

This protective layer, while appearing rusted, adheres to the base metal and protects it from further corrosion.

Gold

Gold is one of the least reactive chemical elements, and its resistance to tarnish and corrosion has made it a sought-after metal for jewelry, coins, and various industrial applications. 

It does not corrode in air or water. Its inertness and non-reactivity to most acids and bases make it one of the most corrosion-resistant metals around. Gold’s resistance to tarnish and its lustrous yellow color have been cherished for thousands of years, making it a symbol of wealth, power, and beauty.

Silver

Silver, while known for its beauty and use in jewelry, does tarnish when exposed to sulfur compounds in the air, resulting in a black silver sulfide layer. However, this tarnishing is only superficial and can often be polished away. 

Platinum

Platinum is a dense, malleable, and highly unreactive metal. Its resistance to wear and tarnish is well-regarded, making it perfect for jewelry, particularly rings and watches. Platinum does not corrode in air and is unaffected by common acids, but it can dissolve in aqua regia (a mixture of nitric acid and hydrochloric acid) and in hot caustic alkalis. 

Magnesium Alloy

Magnesium alloys are lightweight and have a high strength-to-weight ratio. While pure magnesium can corrode, the common commercial alloys like AZ91 are much more corrosion-resistant due to the presence of aluminum (which forms a protective oxide layer) and zinc. 

Methods to Improve Corrosion Resistance for Metal

Protective Coatings

One of the most common ways to protect metals from corrosion is to provide a barrier between the metal and the corrosive environment. This can be achieved by applying paints, varnishes, or other organic coatings.

• Anodizing: This electrochemical process thickens and toughens the naturally occurring protective oxide on metals like aluminum. It results in a hard, durable surface that can also be dyed in various colors. The process provides a barrier and is especially valuable for aluminum materials.
• Galvanization: This involves coating the metal, usually steel, with a layer of zinc. The zinc acts as a sacrificial anode, corroding before the steel does, hence protecting the underlying metal. This is explained in more detail in our article on galvanization.

Plating

Plating is a crucial process that involves depositing a metal layer onto the surface of another metal, either through electrochemical methods or via immersion techniques. This not only enhances the aesthetic appeal of the base metal but, more importantly, bolsters its resistance against corrosion. 

• Nickel Plating: Applied using both electroplating and electroless methods, nickel plating forms a smooth and lustrous surface. The nickel electroplating process uses an electric current to coat the metal, while nickel electroless plating achieves this without an electric current, using a chemical bath instead. Both result in a durable, wear-resistant layer that effectively tackles corrosion.
• Zinc Plating: A popular choice for protecting steel parts, zinc plating involves coating the base metal with a layer of zinc. This sacrificial layer corrodes before the underlying metal does, extending the metal’s lifespan.
• Gold Plating: Beyond its aesthetic appeal, gold plating offers excellent protection against tarnishing and oxidation. It’s often used in electronics due to its good conductivity and resistance to corrosion.
• Copper Plating: Often used as a base layer for other plating processes, copper plating provides enhanced conductivity and promotes adhesion for subsequent plated layers.
• Chromium Plating: Commonly known as chrome plating, this method provides a shiny, mirror-like finish. More than just its visual appeal, chrome plating offers resistance against wear, reduces friction, and guards against corrosion.
• Tin Plating: Used mainly for non-ferrous surfaces, tin plating serves as a protective layer against oxidation and is often preferred for its solderability.
• Phosphate Plating: Phosphate plated coatings, especially those of manganese or zinc, are primarily used to prepare surfaces for subsequent coatings by improving paint adhesion and corrosion resistance.

Alloying

Sometimes, metals are combined with other elements to enhance their corrosion resistance. For instance, adding chromium to steel results in stainless steel, which is notably more resistant to rust.

Passivation

After manufacturing, some metals, particularly stainless steel, have iron particles on their surface. These particles can rust and cause the steel to corrode. Passivation is a chemical process that removes these iron particles and other foreign contaminants, leaving the surface of the metal clean and more resistant to rust.

Environmental Control: 

Controlling the environment in which the metal is used can be a method to reduce corrosion. This may include reducing the salt content in the air, controlling humidity, or using dehumidifiers.

Applications for Corrosion-Resistant Metals

Corrosion-resistant metals are a fundamental component of countless industries, ensuring longevity, safety, and performance in a wide range of applications. Their unique properties have solidified their place in various sectors and for numerous uses.

Marine Industry

Given the harsh, saltwater conditions inherent in marine environments, corrosion-resistant metals are indispensable. Materials like stainless steel and bronze are commonly used for making boat fittings, propeller shafts, and marine fasteners. Titanium, known for its impressive strength-to-weight ratio and resistance to sea water, is utilized for submarine hulls and other deep-sea applications.

Medical Devices

The human body is a corrosive environment, and medical devices need to be made of materials that can resist this corrosion for extended periods. Metals like titanium and certain stainless steel grades are ideal for implants, surgical tools, and other medical instruments due to their biocompatibility and corrosion resistance.

Architecture & Construction

Corten or weathering steel is often chosen for its aesthetically pleasing rust-like appearance and for the fact that, after an initial period of rusting, it becomes highly corrosion-resistant. It’s used in bridges, sculptures, and facades. Stainless steel is also employed in building exteriors, especially in coastal areas where corrosion risks are high.

Automotive Industry

Cars, trucks, and other vehicles are constantly exposed to a variety of corrosive agents, be it salty roads or general moisture. Corrosion-resistant metals like galvanized steel, aluminum, and stainless steel are critical for parts like exhaust systems, engine components, and body panels.

Aerospace

Titanium and certain super alloys are often the metals of choice in the aerospace industry, where strength, lightness, and resistance to environmental factors (like high-altitude conditions) are paramount.

Electronics

Gold, silver, and platinum are not only valuable but are also resistant to tarnish and corrosion. They are used in a myriad of electronic applications including connectors, switches, and relay contacts.

Chemical Processing

Facilities that process chemicals or operate in high-corrosive environments need metals that won’t degrade. Nickel alloys, titanium, and hastelloy are often chosen for tanks, valves, and pipes in such industries.

Jewelry and Minting

Gold and silver are two metals long cherished for their luster and resilience to tarnish. These qualities make them ideal for creating jewelry pieces and minting coins.

Food & Beverage Industry: 

The preparation, storage, and transportation of food and beverages demand materials that won’t corrode easily, especially in acidic or salty environments. Stainless steel is a top choice for kitchen appliances, utensils, food processing equipment, and storage tanks.

Conclusion

Understanding the intricacies of corrosion-resistant metals can be overwhelming, but with the right partner, the challenges become opportunities. At Worthy Hardware, our specialty doesn’t just lie in providing top-notch materials; it’s in delivering precision CNC machining services tailored to your unique requirements. 

So, if you’re seeking unmatched durability in your products and the precision only CNC machining can offer, look no further. Let Worthy Hardware be the cornerstone of your next project. Get in touch today and experience CNC machining at its finest.

FAQ

What is the most corrosion resistant metal?

The most corrosion-resistant metals include titanium, tantalum, and certain grades of stainless steel, like 316 stainless steel.

Why is galvanized steel effective against corrosion?

Galvanized steel is coated with zinc. Zinc acts as a sacrificial anode, corroding before the steel does, thereby offering it protection.

Are all grades of aluminum equally corrosion resistant?

No, while all aluminum forms a protective oxide layer, some grades like 1xxx, 3xxx, and 5xxx are more resistant due to their alloy composition and the additional treatments they undergo.