Metals that don't rust
Which are the metals that do not rust?
Rust is a common iron oxide with a reddish-brown appearance that is formed on a metal when iron and oxygen react with a catalyst such as water or air-moisture, it is a type of corrosion, weakening the metal and causing an aesthetically unpleasant look to the metal. Rust can also be dangerous, causing cuts and scrapes as it flakes off. Removing rust is time-consuming and often unsuccessful, so it best avoided altogether. The best solution is to us metals that do not rust, or ensure you use a finishing surface treatment appropriate to your needs.
As rust is an iron oxide, only metals that contain iron can actually form rust; the most common example of this is steel. However, it's important to remember it is still possible for non-rusting metals to corrode in other ways, so keep this in mind when selecting the right metal for your project.
Here are some of the more useful metals that do not rust.
An extremely abundant and versatile metal, aluminium does not rust as it contains no iron, apart from in some particular alloys. Aluminium does react with oxygen in water or moisture, but the aluminium-oxide acts as a thin corrosion-resistant defensive layer, protecting the metal from further damage.
Copper is a native metal, meaning it can be found in nature in its pure metallic form. Copper cannot rust, but it does oxidise slowly when exposed to air, eventually forming a thin green layer known as patina. As with aluminium, this layer protects the metal but is generally not regarded as a desirable look.
Brass is a zinc and copper alloy, neither of which can rust, it is also stronger than pure copper. This increased strength and ductility combined with good corrosion-resistance make it a classic choice for marine applications. Brass is also smooth, malleable and an aesthetically pleasing colour similar to gold, so it is a popular choice for decorative items, musical instruments and home fittings.
Bronze is another copper alloy, this time combined with tin and sometimes small percentages of other metals. It does not rust as it does not contain iron. While it is a highly corrosion-resistant choice, it can on rare occasions be susceptible to a destructive chemical process known as “bronze disease”, caused by chlorides forming under certain conditions such as submersion in saltwater.
Galvanising is a specific process used to protect iron or steel from rust by coating it with a layer of zinc. This is mostly achieved by dipping the steel in a molten zinc bath of temperatures over 450°C, though there are other methods such as electroplating. Galvanising is not a perfect process as the protective layer can be damaged over time. Still, it is generally a little more workable and far cheaper than stainless steel and offers better rust-protection over time than weathering steel.
Stainless steels containing high enough chromium levels do not rust, as the chromium will oxidise far quicker than iron, creating a chromium oxide layer and preventing the formation of rust. The addition of nickel further enhances a stainless steel alloys rust-proof qualities.
Titanium is an extremely light, strong metal that is resistant to almost all types of corrosion and is used for a variety of applications such as aircraft, sports equipment and marine hardware such as pipes and propellers. However, it is comparatively expensive and not as easy to work with as other metals such as steel or aluminium.
Platinum, gold & silver
Known as the precious metals, platinum, gold and silver are all pure metals, therefore they contain no iron and cannot rust. Platinum and gold are highly non-reactive, and although silver can tarnish, it is fairly corrosion-resistant and relatively affordable by comparison.
Rhodium is a pure metal that does not rust and is sometimes used for plating jewellery. Tin and chromium are pure metals, most often used for coating steel or other rust-prone materials. Chromium is known as chrome when used to plate another metal. A common misconception is that a tin roof looks “rusty” when it is actually the steel underneath that is rusting after the tin layer has been damaged or lost its protection.
At metals4U we carry a wide range of metals that do not rust, so get in touch now to discuss your requirements.