What Is Rust & The Most Common Types of Rust

Dealing with rust can be quite a nuisance, especially if you don’t know what you are doing. Don’t worry, though — I am here to clarify what exactly rust is, the different types of rust that exist, and how to effectively remove it.

You probably know rust as the red or brown flaky coating that appears on metal surfaces after they have been exposed to water. Actually, it is the result of a complex chemical reaction — and there is more than one type of it.

Rusty metal nut.

What Exactly Is Rust?

Rust is the term we use for corrosion and oxidation of iron and its various alloys. It happens when the iron is exposed to both water and oxygen — a process commonly known as oxidation.

Iron reacts quite easily with oxygen, so rust is inevitable if you leave a piece of it exposed to water for a certain period of time. Depending on the intensity of the exposure, rust can take from mere days to several months to form.

From a chemical standpoint, rust is nothing more than iron oxide — Fe²O³. However, it comes in several different forms, depending on the method of its inception. Additionally, it can present itself in a variety of colors, depending on the ratio of oxygen/water that the iron has been exposed to.

Keep in mind that all types of rust and corrosion can be prevented or removed with the proper equipment. I will take a closer look at that further down in the article. Now, let’s explore the most common types of rust out there.

Types of Corrosion

Cavity corrosion is a common type of rust that usually appears on exposed steel used in infrastructure. It results in pits along the surface, which, consequently, dramatically reduce the strength of the metal. The corrosion can create both small and deep pits, depending on the intensity and duration of the exposure. In any case, cavity corrosion is extremely harmful to metals.

Crevice corrosion is a type of rust that commonly happens in confined areas. For example, it can often be found between a bolt and a nut. The tight space aids the development of the rust, which can severely damage the metal it has affected.

Contact corrosion happens when a normal piece of metal comes in contact with a rusty one. Usually, the rust will remain localized at the point of contact. However, in certain cases, it might spread beyond that and affect the rest of the piece.

The Different Colors of Rust

Rust comes in a variety of different colors, based on the circumstances that lead to its formation. Identifying a specific type of rust is often the first step to successfully resolving the problem.

Rust can be yellow, red, and black, among other colors. It all depends on the ratio of water and humidity responsible for its creation.

Yellow Rust

  • Also known as iron oxide-hydroxide (FeO(OH)H2O)
  • Forms in extremely moist environments
  • Usually found in places with still water, such as puddles
  • This solvated type of rust appears to be “dripping” from the metal

Red Rust

  • Also known as hydrated oxide (Fe2O3•H2O)
  • The result of high oxygen levels and moderate moisture
  • A contaminant such as salt will also lead to red rust appearing on metal
  • This type of rust causes uniform corrosion
  • There are no signs of streaking with red rust, which means that it is most likely atmospheric

Black Rust

  • Also known as iron dioxide (Fe3O4)
  • Caused by low oxygen levels and moderate moisture
  • Appears as a thin black layer, almost like a stain
  • Black rust is usually more stable than other types, which makes its spread considerably slower

Brown Rust

  • Also known as iron oxide (Fe2O3)
  • Forms because of high oxygen and low moisture
  • This type of rust is much drier than all others mentioned
  • Just like red rust, brown rust is considered atmospheric
  • Brown rust is generally non-uniform, meaning that it spreads at multiple specific spots, and not along the whole surface

Mixed Rust

It is entirely possible for different types of rust to be present on metal at the same time. As I said, there are a lot of variables when it comes to corrosion. It is possible for an environment to satisfy the conditions for both black and brown rust, for example.

What Causes Rust?

While there are many factors that contribute to the formation of rust, they boil down to three primary categories.

The Manufacturing Process

The procedures followed during the production of a metal object are usually one of the main reasons for corrosion. Metal fabrication often involves heat treating, cold working, and other potentially problematic processes.

Much of what attributes to rust happens before the item is even packaged. The processes in a manufacturing plant are many and complex, so it is no wonder that there are slipups that lead to corrosion in metal elements.

The Type of Packaging

The way metal objects are packaged is crucial for avoiding rust and other related problems. Certain packaging materials can trap moisture, which can easily lead to the formation of rust. Two examples of such materials are non-treated and corrugated paper.

Environmental Conditions

Of course, high temperatures and humidity are among the chief causes of rust, but they are not the only ones by far. Airborne contaminants carry a huge amount of risk, as they can also lead to corrosion in metal parts.

How to Effectively Remove Rust

Rust weakens metal and can lead to a lot of problems in the long run, no matter the size or how the metal object is used. Besides that, it is rather ghastly to look at!

Whether it’s on a car, a bike, a piece of garden furniture, or your favorite tools, you will need to take care of it. Fortunately, if you want to quickly and efficiently remove rust from just about any item, you can try out the methods I have outlined below.

Since all types of rust are generally the same in a chemical sense, these methods are likely to work on any of them. Which method will prove the most effective will largely depend on the item you want to clean.


If you want to remove rust from small elements, vinegar can be extremely efficient. It is acidic, and rust is especially susceptible to acids.

Any type of vinegar should do, even though some claim that apple vinegar provides the best results.

Soak the rusted items for around a day or so, and they should be shiny and as good as new. If there is still visible rust, try the same method again, but keep the metal soaked for a longer period of time (check out this step-by-step guide for more information).

Salt and Lemon

If you need to clean an item that is not small enough to be soaked in vinegar, you can always try using salt and lemon.

First, rub the salt on the rusty area, and then squeeze some lemon juice on top of it. Leave it like this for several hours, and then scrub everything off with a scourer or some steel wool. The rust should be gone — just be careful not to damage the metal by scrubbing too hard!

Baking Soda

If you are out of salt and lemons, the same results can be achieved with some baking soda and a toothbrush.

Mix the baking soda with some water to create a paste — it shouldn’t be too watery. Apply the paste to the rusted area, let it work for a couple of hours, and then use the toothbrush to scrub the whole thing off. That should get the job done.

Get Rough with a Scraper

If you want to remove rust from a large and generally accessible area, you can do it the old-fashioned way and try to remove the rust by scraping it off. Sandpaper, steel wool, wire brush or even a screwdriver can be enough to peel off the rust from the metal.

Of course, you should be careful not to damage the surface underneath the rust. A power sander can do a great job — just make sure you start with rough grain paper and switch to finer grain once the rust starts disappearing.

Use a Rust Removal Product

If the rust is particularly tough, you might need to resort to more extreme measures. Websites such as Amazon have a great selection of rust removal products you can choose from. You should be able to find something truly effective by reading the reviews various users have posted about the best rust removers.

My personal recommendation would be Evapo-Rust. It is a water-based, non-toxic, biodegradable product that works wonders. It removes rust in minutes, and you will not have to scrub or sand anything at all. Since it’s totally safe, you can use it on all types of metal objects, too — even on cookware, antiques, and toys.

Tips on How to Prevent Rust

While removing rust is possible, it would be better to avoid having to do it in the first place. So, here are several handy tips that should help you prevent rust from forming on any metal surfaces.

Keep Everything Dry

When it comes to rust, water is enemy number one. Any metal objects left outside are likely to rust, so make sure you cover them up. Also, if you have to store any metal in a humid place, like a basement, make sure you install a dehumidifier.

Opt for a Protective Coating

There is a variety of protective coating solutions that you can use to keep metal corrosion-free. Those come in the form of sprays or wipes and can be used to make household items, cars, large metal parts, and any outdoor gear resistant to rust.

Prevent Scratches on Metal Surfaces

Cracks and scratches expose the metal and can trap water inside. This is a sure way for the rust to start forming. Therefore, try to prevent scratching whenever possible, and if you can’t, keep the scratched metal somewhere dry.

Regular Cleaning and Maintenance

Rust usually starts small and then spreads everywhere. This is why regular cleaning can stop your metal items from becoming a breeding ground for corrosion. If you notice even a small amount of rust, it’s better to scrape it off immediately. Apply some protective coating afterward to prevent any further oxidation.

Final Thoughts

Dealing with rust at some point is almost inevitable since metal is highly susceptible to it. However, with proper care and maintenance, you can keep your metal items from succumbing to corrosion.

Removing rust is not that hard with household items, let alone with commercial products, designed specifically to eliminate any signs of it. Even though rust comes in different forms, all of them are equally easy to deal with if you know what you are doing.

Hopefully, you are now more informed about what rust is, the different types of rust that exist, and how to remove it properly. For more interesting articles, make sure you browse the rest of my website.

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