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What Metals Rust and Can it be Prevented?

Published by Rapid Metals on

Here at Rapid Metals, we supply an extensive range of products to a wide variety of clients across several sectors, including those who use our metal off-cuts for crafts and to tradespeople. Regardless of which industry our customers come from, one thing they all want to know is how our metals rust, so we’ve made a comprehensive guide on how to remove rust from metal and how you can prevent it.

What Metals Rust?

Rust is a term that refers to the oxidisation of iron, so technically only metals that contain iron can rust. Steel contains iron, so is susceptible to rusting when exposed to water or moisture. If left untreated, the rust will eventually disintegrate the metal altogether.

Whilst metals which do not contain iron technically won’t rust, they can corrode over time. Bronzecopper and brass have a tendency to turn green when exposed to oxygen for a prolonged period of time. 

Whilst it’s highly resistant to rust, stainless steel can corrode in the form of localised pitting.

Gold, platinum and silver can corrode, but because they’re so chemically unreactive, it takes a long time for them to begin to deteriorate.

How to Get Rust Off of Metal

The best and most effective method of how to clean rust off metal will depend on the level of corrosion. If left long enough, rust can entirely dissolve iron and steel to the point that it is unusable. In this instance, removing the rust won’t be a viable option. 

That being said, there are ways to remove rust if it hasn’t yet damaged the metal beyond repair. The first option is to scrape off the rust. Using an abrasive tool, such as a wire sponge or using a paint scraper, will remove a fine layer of rust, but you need to bear in mind that using another type of metal to remove the rust will leave scratch marks that will need to be buffed out once the rust has been removed.

Another removal option that can be done using household items is to do a citric acid soak. Adding store-bought citric acid to hot water and leaving the affected metals to soak in the mixture overnight is an effective method of removing rust, but if your object is larger in size, this won’t be an option.

Chemical rust removers are available to purchase, but they are hazardous and corrosive when they come in to contact with bare skin. If you’re going to use a chemical rust remover, you will need to keep health and safety in mind. Like with citric rust removers, chemical rust removal is only applicable to smaller objects and can be quite expensive. 

If you have a larger area of metal to treat, sandblasting is a good method. A specialised machine is used to propel grit and other abrasive materials towards the affected surface. Whilst this is extremely good at removing the rust, it can cause damage to the underlying metal, so you will need to decide if it’s worth the risk.

How to Remove Rust from Painted Metal

If you’re tackling an unpainted surface such as sheet metal door rust, you have the luxury of being freer with the potential abrasion, but if you’re trying to remove rust from a painted surface such as a car you will need to be more careful. 

Rust is caused by the oxidisation of iron, so the first thing you will need to do when tackling rust on a painted surface is to determine if the metal underneath the paint is rusty, or if there is something on the surface of the paint that is rusty.

It’s a good idea to gently scrape at the surface of the rust to see if it’s surface-level or not. If it is, continue to gently scrape it off, bearing in mind the risk of scratching to the surface. If you find the rust is deeper, you will need to see how deep and if the rust has started to disintegrate the metal as a whole. If it has, this will require a complete replacement as it cannot be saved. If it hasn’t, apply a layer of a solution such as WD-40 for 10 minutes to loosen the rust from the metal and carefully scrape off after. 

When working on a painted surface, we recommend covering unaffected areas that surround the rust to prevent further damage.

How to Stop Rust on Metal

Rust is caused by exposure to air and water, so the most effective way to prevent it is to add a barrier between the metal and the air or water. You can do this in several ways, the most affordable of which being paint. Using oil-based paint is ideal because the oil prevents oxygen and water from coming into direct contact with the metal. Other oil-based products have the same effect. 

Alternatively, adding a powder coating or galvanizing the metal will prevent rust from forming. If you do see a rusty area, remove the rust immediately and apply a coating to prevent it coming back as quickly. Ideally, you would add a preventative substance to the metal to prolong it’s life as early as possible.

Can I Paint Rusted Metal?

Painting rusted metal is possible, but only if the rust is surface-level. If the metal has pits or is corroded structurally, it will need replacing. 

If your metal has surface-level rust, make sure you remove as much as possible before painting. Loose rust will flake off and take the paint with it, so it’s best to scrape it off before you begin. You will also need to prime the metal to ensure the paint adheres to the metal.

It’s inevitable that rust will occur on metals that contain iron, but it isn’t the end of the world and can be tackled and prevented moving forward, but it’s always something to keep in mind when using steel and iron. 

If you have any questions about rust and preventing it, or about any of our metal products, please get in touch with our team today and we will be more than happy to offer assistance.

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