corrosion resistant metals

4 Types of Metal That Are Corrosion Resistant or Don’t Rust

We usually think of rust as the orange-brown flakes that form on an exposed steel surface when iron molecules in the metal react with oxygen in the presence of water to produce iron oxides. Metals may also react in the presence of acids or harsh industrial chemicals. If nothing stops the corrosion, flakes of rust will continue to break off, exposing the metal to further corrosion until it disintegrates.

Not all metals contain iron, but they can corrode or tarnish in other oxidizing reactions. To prevent oxidation and breakdown of metal products, such as handrails, tanks, appliances, roofing or siding, you can choose metals that are “rust-proof” or more accurately, “corrosion-proof.” Four basic types of metals fall into this category:

  • Stainless steel
  • Aluminum metal
  • Copper, bronze or brass
  • Galvanized steel

Stainless Steel

Stainless steel types, such as 304 or 316, are a mix of elements, and most contain some amount of iron, which easily oxidizes to form rust. But many stainless steel alloys also contain a high percentage of chromium – at least 18 percent – which is even more reactive than iron. The chromium oxidizes quickly to form a protective layer of chromium oxide on the metal surface. This oxide layer resists corrosion, while at the same time prevents oxygen from reaching the underlying steel. Other elements in the alloy, such as nickel and molybdenum, add to its rust-resistance.

Aluminum metal

Many aircraft are made from aluminum, as are car and bike parts. This is due to its light weight, but also to its resistance to corrosion. Aluminum alloys contain almost no iron and without iron, the metal can’t actually rust, but it does oxidize. When the alloy is exposed to water, a film of aluminum oxide forms quickly on the surface. The hard oxide layer is quite resistant to further corrosion and protects the underlying metal.

Copper, Bronze and Brass

These three metals contain little or no iron, and so do not rust, but they can react with oxygen. Copper oxidizes over time to form a green patina, which actually protects the metal from further corrosion. Bronze is a mixture of copper and tin, along with small amounts of other elements, and is naturally much more resistant to corrosion than copper. Brass is an alloy of copper, zinc, and other elements, which also resists corrosion.

Galvanized Steel

Galvanized steel takes a long time to rust, but it will eventually rust. This type is carbon steel that has been galvanized, or coated, with a thin layer of zinc. The zinc acts as a barrier preventing oxygen and water from reaching the steel, so that it is corrosion protected. Even if the zinc coating is scratched off, it continues to protect nearby areas of the underlying steel through cathodic protection, as well as by forming a protective coating of zinc oxide. Like aluminum, zinc is highly reactive to oxygen in the presence of moisture, and the coating prevents the iron in the steel from further oxidation.

Industrial Metal Supply carries a wide range of rust-resistant metals for a variety of applications.


7 Amazing Things Made from Bronze

Like brass, bronze is an alloy primarily made of copper. But where brass combines copper with zinc, bronze is made of copper and tin, often mixed with small amounts of other metals and non-metallic elements, such as lead and silicon.

By combining soft copper with brittle tin, the result is an alloy with improved strength and hardness. Bronze is also mon-magnetic, corrosion resistant, and exhibits good thermal and electrical conductivity.

Bronze is sold in the form of tubes & rods, ingots or sheet. Two main types of bronze sheet – silicon bronze sheet and bearing bronze sheet – can be found in a variety of industrial applications. Silicon bronze sheet is relatively easy to machine, while working bearing bronze sheet requires more fabrication expertise.

Silicon bronze (C65500) is a low-lead brass alloy that is generally composed of 96% copper, along with silicon and possibly small amounts of manganese, tin, iron, or zinc. It is known for its easy pouring ability and attractive surface finish, as well as a superior corrosion resistant makeup, even when submerged in liquids including salt water, fresh water, most acids and organic chemicals.

Bearing bronze (C93200) also offers high corrosion resistance, as well as excellent wear resistance and high hardness. As the name suggests, bearing bronze sheet is most often used for bearings, bushings, and similar applications.

The many beneficial characteristics of bronze make it useful for a wide range of applications, including:

Springs – Phosphor bronze precision-grade wire is used to form compression springs and electrical contacts. Its corrosion resistance, high strength, and low coefficient of friction, make it a popular substitute for costlier alloys, such as beryllium copper.

Marine architecture – With its high corrosion resistance, high strength, and natural lubricity, bronze is ideal for use in saltwater and freshwater applications, such as engine parts, pumps, propellers, and ship’s bells.

Industrial castings – Bronze is relatively easy to machine and pour for castings and results in components, such as pumps and valve stems, which can withstand high wear and abrasion. Silicon bronze also has self-lubricating qualities which make it ideal for bearings and bushings in a wide range of applications, including small electric motors and automobile transmissions.

Sculpture – Bronze has been used to make beautiful works of art in many cultures for centuries. When silicon was introduced to the alloy mix in the 20th century, silicon bronze became the primary form used in sculpture.

Musical instrument strings – Bronze wound strings are used for acoustic guitars, pianos, and traditional instruments like the sitar. Bronze windings around steel or nylon cores provide a much warmer sound than other metals, especially for lower notes.

Safety tools – Steel tools such as hammers, mallets and wrenches, can cause unsafe sparks when used near flammable or explosive gases and vapors. Bronze is non-magnetic and spark-free, making it a much safer choice for preventing arc flash in hazmat areas.

Bronze wool – As a substitute for steel wool, bronze wool is used to polish and sand wood and metal surfaces. Because it resists corrosion and doesn’t shed like steel wool – leaving particles that could cause electrical shorts – bronze wool is ideal for industrial, construction, and marine applications and won’t leave stains on wood.  
Questions? Industrial Metal Supply stocks a variety of silicon bronze and bearing bronze materials. We stock bronze in all forms: 


Brass vs Bronze

Bronze and brass are metal alloys that both incorporate copper into their composition. To the untrained eye, the two alloys look fairly similar. However, the color, durability, and application of these metals are actually quite different. Below, we’ve outlined some of the unique properties that define brass and bronze.

Brass 

  • Composition: There are dozens of different brass alloys, each with its own proportion of copper and zinc. There may also be tiny amounts of aluminum, phosphorus, manganese, and other metals.
  • Color: Depending on the amount of zinc in the alloy, brass can vary from a dull gold color to a slightly more reddish hue.
  • Historical Origin: Used since prehistoric times, brass became much more popular after the medieval period, when people learned how to create the copper-zinc metal. In the beginning, brass was made by smelting copper ores, which fortuitously has high proportions of zinc.
  • Properties: Brass is more malleable than bronze, although certain alloys are considered soft and hard brasses. It’s not complicated to recycle brass alloy, and when collected from scrap yards, it’s also an easy material to cast into billets. It also has a lower melting point than bronze.
  • Practical Use: Mainly used for decoration, brass is also harnessed to create musical instruments (trumpets, trombones, etc), doorknobs, plumbing, ammunition, and certain electronics.

Bronze

  • Composition: Like brass, bronze is mainly composed of copper, but also has about 12% tin, along with smaller amounts of aluminum, silicon, manganese, or zinc.
  • Color: Depending on the composition, bronze can have a mix of browns, reds, and yellows. It usually looks reddish brown.
  • Historical Origin: Discovered before brass, bronze has been used in some form since 5000 BC. The earliest bronze used arsenic instead of tin, and arsenic bronze artifacts were found in the Iranian Plateau between Western and Central Asia. Tin bronze was introduced around 3500 BC.
  • Properties: More brittle than brass, bronze has a higher melting point (around 950ºC). Its strong resistance to corrosion makes the alloy useful for coastal, seafaring applications.
  • Practical Use: Sculptures, electrical connectors, drum cymbals, boat fittings and propellers.