What is Rust?

Michael Pollick
Michael Pollick

Rust is another name for iron oxide, which occurs when iron or an alloy that contains iron, like steel, is exposed to oxygen and moisture for a long period of time. Over time, the oxygen combines with the metal at an atomic level, forming a new compound called an oxide and weakening the bonds of the metal itself. Although some people refer to rust generally as "oxidation," that term is much more general; although rust forms when iron undergoes oxidation, not all oxidation forms rust. Only iron or alloys that contain iron can rust, but other metals can corrode in similar ways.

Oxidized metal gears.
Oxidized metal gears.

The main catalyst for the rusting process is water. Iron or steel structures might appear to be solid, but water molecules can penetrate the microscopic pits and cracks in any exposed metal. The hydrogen atoms present in water molecules can combine with other elements to form acids, which will eventually cause more metal to be exposed.

A paste of baking soda and water can remove rust from metal.
A paste of baking soda and water can remove rust from metal.

If sodium is present, as is the case with saltwater, the corrosion is likely to occur more quickly. Meanwhile, the oxygen atoms combine with metallic atoms to form the destructive oxide compound. As the atoms combine, they weaken the metal, making the structure brittle and crumbly.

Rust, also known as iron oxide, happens when iron or an iron alloy is exposed to oxygen and moisture.
Rust, also known as iron oxide, happens when iron or an iron alloy is exposed to oxygen and moisture.

Some pieces of iron or steel are thick enough to maintain their integrity even if iron oxide forms on the surface. The thinner the metal, the better the chance that rusting will occur. Placing a steel wool pad in water and exposing it to air will cause rusting to begin almost immediately because the steel filaments are so thin. Eventually, the individual iron bonds will be destroyed, and the entire pad will disintegrate.

A dehumidifier may be used to reduce the chances of rust formation.
A dehumidifier may be used to reduce the chances of rust formation.

Rust formation cannot be stopped easily, but metals can be treated to resist the most damaging effects. Some are protected by water-resistant paints, preventative coatings or other chemical barriers, such as oil. It also is possible for one to reduce the chances of rust forming by using a dehumidifier or desiccant to help remove moisture from the air, but this usually is effective only in relatively small areas.

Steel is often galvanized to prevent iron oxide from forming; this process usually involves a very thin layer of zinc being applied to the surface. Another process, called plating, can be used to add a layer of zinc, tin or chrome to the metal. Cathodic protection involves using an electrical charge to suppress or prevent the chemical reaction that causes rust from occurring.

Water molecules can penetrate the tiny openings in exposed metal.
Water molecules can penetrate the tiny openings in exposed metal.
Michael Pollick
Michael Pollick

A regular wiseGEEK contributor, Michael enjoys doing research in order to satisfy his wide-ranging curiosity about a variety of arcane topics. Before becoming a professional writer, Michael worked as an English tutor, poet, voice-over artist, and DJ.

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Discussion Comments


Does it affect water pipe lines?


Rust occurs when iron water and oxygen mix together. It's normally called oxidation. Rust is a chemical reaction.


I know what rust is but why does it form? Can metals that are not alloys of iron rust?


I find it so interesting that people usually fight rust wherever it appears, but many others find the texture so appealing. I see rust textures in advertisements, games and movies regularly.


What are human impacts on rust?


How do you measure rust?


What is the best way to measure rust?


Do you have to have oxygen for something to rust?


There seem to be a lot of questions on how to prevent rust, but how would you speed up rusting without salt water, and what's all this about vinegar?


How is rust so damaging?


Why does rust have that red color though?


What happens when you take a mixture of bleach, salt and water, put aluminum in it and cover it with a thin layer of vegetable oil? Will it corrode, and if so, will it corrode faster in mild temperatures, cool or under a lamp that is 40 watts?


I recently did a science fair project on rusting. I am in year 9. I used water spray, salt water, tap water and white vinegar (mixed with water). I used three iron strips in each. They were all submerged completely except for the spray of course. In the end vinegar rusted the most. It formed a lot of rust and it lost the most weight too. Tap water was next then salt water.

From the research I've done, vinegar removes rust, and salt water is supposed to rust a lot. I am supposed to explain why what happened happened. I can't find anything, though. Can anyone help me? It's urgent.


I'm sorry, but I can't find the author of this page! I need it for my bibliography! please help!


what will be the effect if a baby puts a rusty object on his mouth?


How would I cite this?


Thank you guys so much! This helped so much with my science fair project! Thanks. This was very useful.


Does the density of a liquid affect the speed of rusting a metal?


I'm doing a project on the speed of rust in different liquids such as coke. Can anyone provide any help?


Only iron oxide is rust. Other metals undergo oxidation to form oxides, but the resulting material is an iron oxide, not rust.


Does the presence of rust on a surface make that surface more prone to oxidation? Let's say, if a metal box was left to the elements and produced some rust, if you took said box, cleaned it and kept it isolated from the elements (a.k.a. outside), would that box be more prone to oxidation in the future?


So many questions on here with no or bad answers.

Will soda (coke) oxidize (rust) metal? Yes. All sodas contain phosphoric acid. This is where the bubbles come from, this also decreases the pH of the soda and speeds up the rusting process. P.S. To the doctor who said co2 does not cause oxidation you are wrong co2 is corrosive.

What gives rust its orange-red color? The element Fe (iron) is what turns rust red.

Does the presence of sodium speed up the rusting process? Yes. Sodium increases the conductivity of water, making it a better electron transfer medium and speeding up the oxidation process.

Any health effects upon exposure to deep well water containing rust due to corrosion in the pipeline?

Depends on many factors, generally speaking, however, no. However, rust on piping makes an excellent site for harmful organisms to form colonies, and severely rusted pipes tend to have poor seals, allowing a whole host of things to seep into your water. If you have high iron in your water it is generally a good idea to find a way to reduce it either though treatment (which well water often needs anyway) or replacing damaged pipes.

How can rust be prevented with just a simple substance? There are whole fields of science dedicated to this question. Generally speaking, coating iron in any compound that seals off the iron surface from oxygen: e.g., paint, plastic, oil.

What are the positives and negatives of rusting? Well, the negatives part is easy. If the metal rusts away, it can fail, potentially causing great damage or bodily injury. The positive is a bit harder to answer. The short version is rusting is bad. However, not all rust is the same. For example, the Statue of Liberty was originally the color of a freshly minted penny. Over time as the surface copper oxidized, it formed a hard protective layer protecting the rest of the metal surface from exposure to oxygen, and greatly slowing down the "rusting" of one of the world most iconic national treasures.

How does the chemical change take place (from metal+water+oxygen = rust)? I couldn't think of a way to explain this easily but the information is available online.

Why does the metal rust more when the plating is scratched? Often metal is treated to resist rusting, but this treatment is only "skin deep." You create a galvanic cell, dramatically increasing the flow of electrons in a very small area.

Do you think iron would rust slowly, quickly, or at all in distilled water? Very slowly, or depending on what exactly your "iron" is made from, not at all.

“I am doing an experiment trying to find out in what type of water iron would rust the fastest...” The slowest will be distilled water by far. The tap water and salt water could be a toss up depending on where you get your tap water from, and how much salt you put in it. Also make sure you use the distilled water to make your salt water otherwise you will have salty tap water and it will spike your results.

As for removing them from the water, I would say no. However, drawing some of the water off, and pouring it back into your sample jar several times a couple times a day could increase the dissolved oxygen content of your water samples and will increase the rate of oxidation.

How long do you think an experiment like this would take? Depends how much rust are you looking for, the quality of your iron and the properties of your sample water types. Most often, nails are galvanized or treated in some way to resist rusting and may takes weeks or longer to show any real signs of rusting.

Why does water rust less than coca cola, or apple juice? And why does the iron in the apple juice turn black? Coca-Cola and apple juice have a lower pH than water. Low pH solutions will rust iron faster, and the reason it turns black in apple juice is much like a blue and yellow marker make green; the compounds in apple juice, when mixed with iron, form a material black in color.

I have an indoor water fountain with metal cups are now rusting...” To remove the rust, drain the fountain let it dry, Go buy CLR and a stiff brush rinse and scrub. As for preventing the rust from coming back, the short answer is there's nothing you can do.


if i put an iron nail in hydrochloric acid and another in sea water (salty water) which would rust more?


I am doing a science experiment. What will rust faster in just plain tap water - an iron nail or a small piece of steel wool? I am guessing steel wool because of the surface area. Can anyone verify this for me? Thanks so much!


If a piece if rust is say, 1mm (0.039'') thick, what thickness of steel has been lost? I have heard a wide variance of answers, so is there a definitive one please?


someone asked how does rust harm you. here's the answer: it doesn't. it harms metal.


Thanks for the info!


How does rust harm you?


thanks this really helped because I am doing a science fair project on how to make a nail rustproof. all of this information was very helpful!


This really helped me with my science project I'm working on. now we needed five references and I have picked up the most and interesting facts on this website. hopefully my teacher will think my project is decent.


can liquids form rust?


what chemical and physical changes happen to metal when it rusts?


I have a indoor water fountain with metal cups which is where the water flows over. The metal cups are now rusting and I would like to know how to remove the rust and refinish the cups so they won't rust anymore.


This really helped me! I am so thankful I've been looking for a long time for information about rust.


I'm doing a science fair project on "which liquid rusts nails the fastest, water, vinegar, coke, or orange juice. I don't know what to start researching. What do I do?


Why do nails rust with exposure to salt water and not to vinegar?


Rust is formed by oxidation and oxygen mixing together on the surface of metal or iron cause it to become bumpy and brown-red like.


Is rust bad for your health?


How can we make rust on metal without water?


how do you remove rust?


I have a problem concerning rust on aluminum?

Anybody know of a cause, please help me.


can fizzy drinks make something rust and why?


why does rust gives a reddish color?


here we know about rust. it's very easy to learn.


what procedure should I use to make iron rust with which liquids?


Apparently coca cola can help remove rust. does anyone know if tap water causes rust more than coke?


i don't understand. Can any substance make something rust?


it rusts faster when the plating is scratched off

because it opens the pits and pockets and lets the water and air flow through it quicker.


i highly disagree that rust grows faster in salt water. it grows quicker in regular water.


rust grows quicker in salt water. a good experiment would be: air, water, salt water.


rust is bad.


OK I am doing a science experiment and does vinegar, tap water, or Sprite make a fishing hook rust the fastest?


how can i separate the mixture of rust and magnetite layer?


I just did an experiment and I found out that vinegar will rust things the most in four weeks.


i need help badly. what helps rust grow the fastest? lemon juice, water or vinegar? please respond. Quickly!


thanks heaps. that's really good.


I am also doing a science experiment. Which metal )steel, aluminum, copper) will rust the fastest in water, lemon juice, and ammonia?


Are there any environmental effects of rust?


one way to get something to rust is to fill up a cup with water. Then put a nail in the cup filled with water. Once you do that put in salt. After that sit back and watch the nail rust away.

If it doesn't I recommend using a different kind of salt.


How do different liquids affect the amount of rust on metal?


I'm doing the following experiment: I put

in four cups different materials like: a penny, a bolt, a paper clip, an aluminum. Then I put a little bit of water in each cup. In each cup I put different drinks like: water, water with salt, coke, orange juice, vinegar. In those materials I put five pennies, a bolt, paper clip and aluminum. How can I do this project? What is the problem, hypothesis,procedure, data, what's happening and conclusion. If I have a question, can I write you again?


I'm also doing a science fair project (which is a huge pain in the but by the way!), but this site has helped me a lot. You see, my project is on what dissolves the rust on a rusty nail the most: bleach, water, baking soda, salt or sea salt.


I'm doing a science fair on which dark soda will remove rust from a rusted nail the fastest and i want to know how long it takes so i can see how long i can keep an eye on it.

thank you so much! this site helped me a whole bunch! -Kayla


Why does water rust less than coca cola, or apple juice? And why does the iron in the apple juice turn black?


Which liquid will rust a nail the fastest, tap water, lemon juice or coke?


This has really helped me with my science fair project.


I'm doing a science project on what makes a nail rust faster: tap water or salt water? could you tell me how long it usually takes a nail to rust so i can figure out when i need to get it done?


i have six test tubes. One contains tap water, the other distilled water, the other distilled water with salt, the other distilled water with oil, the other dry sand and the final one wet sand and all off them had one nail inside. i would want to know the effects.


I would like to know if you using a rusty hair clip in your hair would affect your scalp, and your hair growth.


This website really helped me with my project.


Some metals that can rust are steel, copper and bronze. But anything with iron in it will rust.


i am doing a science fair project and i would like to know what metals can rust.


can a nail rust in fresh water?


I need to know what gets rid of rust faster?

vinegar or baking soda? please let me know. Thank you. (:


i read this thing where you put 4 tsps. of bleach and 2 tsps. of vinegar into a jar with whatever you want to rust, fill it up with water just past the metal. it'll rust in about 5 minutes.


can rust form on any steel?


I can't find ten good facts about rust. can you help me? i am doing a science fair project. please help.


Can rust be immediate or does it take a few days?


How does rust get in iron or steel?


why don't you give the author because people are using this as bibliogrophy and you have to have the author for that! Duh!


Thank you for the information. This is just what i needed. Thank you.


rust is browny orange.


Oh gee, thank you so incredibly much. I am doing a science project, and this information will definitely help me ace it! Go science!


hey thanks so much. doing a science project and this will totally get me to the county fair. Thanks so much!


The term "rust" refers only to oxides of iron - therefore it is not correct to refer to oxides of other metals (such as aluminum and copper) as rust.

In addition oxidation is the processes by which rust, and other oxides, are formed - therefore the first sentence is also incorrect. It would be more accurate to equate "rusting" and "oxidation", however only when referring to iron.


Please can you tell me the outcome of the following reactions with their equations:

1) Iron left to rust for a few days in Aqueous HCl.

2) Iron left to rust for a few days in Aqueous NaCl.

3)Iron left to rust for a few days in Aqueous

HNO3(Nitric Acid).

4) Iron left to rust for a few days in Aqueous

NaNO3(Sodium Nitrate).


How long it would it take enough rust to build up inside a 100 lb. oxygen tank to cause it erupt when full?


i'm going to do a project called 'which metals will be effected by salty water?' can you tell me what grade project this is, because i want to do like a 6th or 7th grade project although i'm in 5th grade? can you please explain this to me in some easier words?


I am about to do an experiment involving the rusting of nails.

Can you tell me of an unusual way to rust nails?

I will be using 4 test tubes.

One will have a galvanized nail and the rest will be regular iron nails.

Thanking you,



i'm doing a project about oxidation of *rocks* and i have no idea what it is! please help. it would be really nice 'cause I found oxidation pictures but no info... thanks!


I am doing a project on what how does coating an iron nail with nail polish affect the rate that it will rust in vinegar? - Briana 4th grade


i'm doing a science project. so how could you prevent metal from rusting without paying the price?


Is rust another metal on top of the metal when the water hits it?


is rust harmful to the skin?


does salt water rust metal?


which kind of liquid rusts iron the fastest? -Michael, 7th grade


why do we get tetanus? is there anyway to prevent from this disease?


1 Do you think iron would rust slowly, quickly, or at all in distilled water?

2 I am doing an experiment trying to find out in what type of water iron would rust the fastest; we are doing so with iron nails and salt water, tap water, and distilled water... should I leave the iron nails in the water the whole time, or occasionally remove them from the water?

3 How long do you think an experiment like this would take?


Wait, so are there any other substances (other than steel or iron) that can have rust grow on it?

And does the original way of using baking soda and vinegar actually take off 100% of the rust on any substance?


wait so the scientific name is oxidation?


I am doing a report and this will definitely help me get a good grade!!!


what are the 2 types of rust?


What is the most efficient way to treat rust. Please reply. I have an assignment on this.


why is it that only metals experience corrosion? what is it about their structure that makes them experience corrosion?


Well robbi i think it is because there is more area for the water and oxygen to get to create more rust. Nick Rodriguez 8th grade


1. How does chemical change take place(from metal+water+oxygen = rust)?

2. Why does the metal rust more when the plating is scratched?


i heard that heat and sand get rid of rust or just keep scrub it the rust with warm water and then i think that should do it.


What gets rid of the rust?


what are the positives & negatives of rusting ?


I know the answer to some of these Q's:

1. No, It's not bad for you.

2. I don't think so, but I'm not sure.

3. No, the gas in it is CO2, (Carbon Dioxide) the fizziness does nothing unless the Coke is mixed with O2. (Oxygen)

4. Copper, iron and steel rust orange/red because that is how the oxygen mixes with the metal.

5. Paint and oil are great substances for prevention of rust.

6. It depends how much O2 is in the air that you put the rusting metal in.

Yours Faithfully,

Dr Ryuta Kawashima

P.S. Is Mascara good for the bugs on your eyelashes?


how long does the rusting process take?


how can rust be prevented w/ just a simple substance?


What gives rust its orange-red color?


can coke make something rust?


Does the presence of sodium speed up the rusting process?


Any health effects upon exposure to deep well water containing rust due to corrosion in the pipeline?

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