Everything you wanna know about Rusting

January 11, 2023
A rusty car

Why write this article

As a stainless steel manufacturer, we are glad that more and more people pay attention to the topic of “metal rusts”. The original intention of writing an article is to let everyone have a systematic and comprehensive understanding of “metal rust”.

The Principle of Rusting

Rust is essentially an oxidation reaction of metals. The most common rust phenomenon in life is the oxidation reaction of iron products with oxygen after long-term exposure to the air.

3 Conditions for Metal to Rust

We know that moisture is what makes iron rust easily. In fact, only water will not make iron rust. Iron is oxidized to rust (iron oxide) only when enough oxygen is dissolved in the water it comes in contact with.

Note: The actual composition of these dark red rusts is more complex. It is the product of the combination of “iron oxide” (Fe2O3) and “water”, which we usually express with Fe2O3·nH2O.

In summary, metal rust (oxidation) requires three conditions: oxygen, electrolyte, and the presence of metal as an anode.

  • Oxygen refers to the oxygen contained in the air.
  • Electrolyte refers to water or water vapor in the air.
  • Anode refers to the metal being oxidized, such as pig iron.

When these three conditions are met, the oxidation-reduction reaction of “rusting” will begin to occur. So on the whole, whether iron will rust or not depends mainly on oxygen and moisture.

Does only contact with water or oxygen make iron rust?

Will not. We can prove it through the following experiment.

Prepare three iron nails and put them in three test tubes respectively.

  • No. 1 test tube is filled with dry air and sealed (to isolate the moisture in the outside air).
  • Test tube No. 2 is filled with water, the iron nail is covered with water, and the top of the water is sealed with a layer of oil (to isolate the air).
  • The No. 3 test tube is half filled with water, so that part of the iron nail is in the water and part is exposed in the air.

After a period of time, only the iron nails of test tube No. 3 were rusted, and test tubes No. 1 and No. 2 were not rusted. This proves that mere air or mere moisture cannot rust iron.

Some knowledge you may be interested in

  • After a piece of iron is completely rusted, its volume can expand 8 times.
  • Iron is heavier when rusted, about 3 to 5 times its original weight.
  • Humidity has an effect on metal rusting. The critical humidity of many metals is between 50% and 80%, and steel is about 75%. If the ambient humidity is greater than the critical humidity of the metal, it will accelerate the occurrence of metal rust.
  • The temperature has an effect on metals. It is generally believed that when the working temperature of a metal reaches 30% to 40% of its melting point (absolute temperature), it can be considered a high-temperature corrosion environment. The higher the temperature, the higher the chance of metal corrosion and the faster the rate.

How to Prevent Metal From Rust

As mentioned earlier, metal rust is related to oxygen and water on the metal surface. Therefore, anti-rust measures start from these two aspects:

  • Keeping the surface of iron products clean and dry is a basic method to prevent iron products from rusting.
  • Add a protective film to the metal to isolate oxygen and water:
    • Cover the metal surface with mineral oil, paint or fired enamel, spray, etc. (Carriages and buckets are often painted; machines are often painted with mineral oil.)
    • A layer of other metals that are not easy to rust is plated on the metal surface by electroplating, hot-dip plating, etc. These metals can be zinc, tin, chromium, and nickel. A dense oxide film can be formed on the surface of this layer of metal, which can prevent iron products from rusting due to contact with water, air, and other substances.
  • Alloys are used instead of single metals. For example, add some other metals to iron to make a stainless alloy. After the oxidation of this kind of alloy, a very dense oxide layer is formed, which can isolate the air inside the alloy from the outside, so as to achieve the purpose of rust prevention. (Stainless steel falls into this category.)

Prevent car rust

Sealing glaze for vehicles with soft paint finish

During high-speed driving, some vehicles with soft paint surfaces are hit on the body by wind and sand particles, which may cause fine scratches. At this time, the body should be sealed with a glaze. This can form a strong protective film in the form of a net, improve the hardness of the paint surface, and prevent the car from rusting.

Use car covers sparingly

When it is windy and rainy, the paint of a vehicle parked outside will be repeatedly whipped by the inner layer of the car cover. This has resulted in countless small scratches on the car body, making the car body easy to rust.

How to Remove Rust

How to Remove Rust

Rust is a brownish-red substance that absorbs moisture very easily, which further accelerates the rusting of iron.

If you do an Internet search for “rust removal,” you’ll probably get something like this:

To remove rust, you can use various tools to shovel it off, or soak it in a dilute acid solution (dilute hydrochloric acid, dilute sulfuric acid) to dissolve it.

But sometimes we can’t find the right tool and acid solution. Therefore, this article sorts out some commonly used home rust removal methods to solve the urgent need.

1. Use materials commonly used in the home to remove rust

  • White vinegar. Using white vinegar will chemically react with and break down the rust on the metal.
    • You can soak the metal in white vinegar for a few hours, then wipe the rust off with a rub.
    • If the item is too large to be submerged directly in the white vinegar, you can pour a layer of white vinegar on top and allow it to set.
    • You can also dip a rag in vinegar and wipe the metal.
    • You can try dipping aluminum foil in vinegar and using it as a brush to scrub away the rust. Aluminum foil is less abrasive than steel wool, but still has the ability to remove rust.
    • You can use regular table vinegar and let rusty metal soak in vinegar for up to 24 hours before cleaning. This method does not require much scrubbing effort.
  • Limes (lemons) and salt.
    • Use lime and salt Sprinkle the salt over the rusted area to coat it thoroughly, then squeeze the lime juice over it. Use as much lime juice as you can get your hands on, and let the mixture sit for 2 to 3 hours before rinsing off the mixture.
    • Use the rind of the lime to wipe off the mixture. The lime zest should be enough to remove the rust without further harming the metal.
  • Baking soda.
    • Mix the baking soda and water together until the mixture is thick enough to coat the metal. Give it some time to set before washing it off. You can try using a toothbrush to remove the baking soda, then rinse with water.
    • You can dilute the baking soda with water if you like, there is no set mixing ratio for this method.
  • Potatoes and dish detergent.
    • Halve the potatoes and cover the cuts with dish soap.
    • Put the potatoes on the metal and let them sit for a few hours.
    • To reuse, you can cut the used end back off and apply more dish soap to soak it into the metal longer. If you don’t have dish detergent, cover the cut potatoes with baking soda and water.

2. Remove rust with store-bought supplies

  • Chemical rust remover.
    • There are many different chemicals that break down rust. They are usually made from phosphoric or oxalic acid.
    • It can damage the skin if it comes into direct contact, so take protective measures when using chemicals to break down rust.
    • Each rust remover is used differently and the directions on the rust remover product must be followed. These chemicals usually need to sit for a while and then need to be scrubbed off, so be prepared to do extra work.
    • These products are expensive and should only be used for small-scale rust removal jobs, not for larger rusted items.
  • Rust converter.
    • Rust converters stop the growth of rust areas on metals. Rust converters are similar to spray paint and also act as a protective primer coat. While it stops the rust from growing, it may not be effective and quick enough to completely remove it from the metal.
    • This method leaves a rough texture under the lacquer coat.
  • Sanding tools.
    • Use a sanding tool to scrape away the rust. This method is laborious, but it will allow you to effectively remove rust just by scratching.
    • You can use tools from your garages, such as a screwdriver, or rent tools from a hardware store. Steel wool is also easy to use, and you probably already have one at home without having to buy one.
    • You can use an electric sander to remove rust from large metals. Start with the coarsest abrasive grains and slowly transition to finer grains to minimize the roughness of the metal.
    • You can use any metal tool to scrape off the rust, but remember to use fine-grit sandpaper afterward to smooth out any marks that may have been left by the scraping process.

3. Remove rusty spot

  • Remove rust stains from clothing.
    • If your clothes come into contact with rust, use lemon juice and water to remove any remaining rust spots on your clothes.
      • Apply lemon juice to the affected area of clothing, but do not allow it to dry. Rinse off the lemon juice and rust spots with clean water.
      • For heavy fabrics with severe rust spots, in addition to lemon juice, you can also apply salt to the rust layer.
  • Remove rust stains from brick or concrete.
    • Mix 7 parts lime-free glycerin, 1 part sodium citrate (available at pharmacies), 6 parts lukewarm water, and enough calcium carbonate powder (chalk) to form a thick paste.
    • Apply the thick paste to the rusted area and let it harden.
    • Use a metal tool to scrape the paste off after it hardens. If the rust cannot be completely removed, you can use the same method and apply the thick paste again.
  • Removes rust from porcelain and ceramics.
    • Make a paste of borax and lemon juice and apply it to the rust spots.
    • Then scrape it off with a pumice stone and repeat if necessary. The ceramic or porcelain needs to be dried afterward to prevent re-rusting.
    • This method should not be used on ceramic cookware as it can scratch the cookware.
  • Removes rust spots on stainless steel.
    • Rub vigorously all over the stainless steel with very fine emery paper.
    • Then rub all over the stainless steel with a slice of onion.
    • Then wash with hot water.

How to Make Metal Rust in Minutes

Rust Metal Artwork

Rusting metal isn’t all bad. Rusted metal (especially artwork) tends to give a special aesthetic experience. Here are two ways to make metal rust quickly.


  • The following methods are all for metals that are prone to rust, such as cast iron and wrought iron.
  • You should handle hydrogen peroxide very carefully, it can irritate the skin and mucous membranes.

Using Hydrogen Peroxide and Salt

Method features

  • A well-ventilated place is required
  • The rate of rusting can be controlled by varying the amount of hydrogen peroxide sprayed.
  • The degree of rusting can be controlled by varying the amount of salt sprinkled in.

Prepare materials

  • Hydrogen peroxide
  • Salt
  • Spray bottle


  • Find a well-ventilated area.
  • Fill a squirt bottle with hydrogen peroxide.
  • Spray hydrogen peroxide on metal objects, slowly and carefully. Avoid contact of hydrogen peroxide with eyes or skin. The more you spray, the more it will help speed up the rusting process.
  • Sprinkle the salt on the metal surface while the hydrogen peroxide is still wet. Then you can see the metal slowly rusting. The amount of rust depends on how much salt is sprinkled.
  • Wait for the metal item to dry before wiping off the salt. Do not remove the salt while the peroxide is still wet, as this will disrupt the rusting process and cause the rust to appear blotchy.

Never use bleach and vinegar

There is a method online that uses a mixture of vinegar and bleach to spray the metal. This is a very dangerous practice.

What happens when bleach and vinegar are mixed?

Chlorine bleach contains sodium hypochlorite, or NaOCl. Sodium hypochlorite in bleach is actually in the form of hypochlorous acid:

NaOCl + H 2 O→HOCl + Na + + OH 

Hypochlorous acid is a strong oxidizing agent. This is why bleaching and sanitizing are so good. But if you mix bleach with an acid, chlorine gas will be produced. For example, mixing bleach with a toilet cleaner that contains hydrochloric acid produces chlorine gas:

HOCl + HCl·H 2 O + Cl 2

Mixing bleach with another acid, such as the acetic acid in vinegar, yields essentially the same result:

2HOCl + 2HAc + Cl 2 + 2H 2 O + 2Ac  (Ac:CH 3 COO)

Although pure chlorine is greenish-yellow, the gas from the mixed chemicals is diluted in the air. It is invisible.

Chlorine attacks mucous membranes such as the eyes, throat and lungs and can be fatal.


Is tetanus related to rust?

No. Tetanus has nothing to do with rust itself.

Tetanus is a serious infection caused by the bacillus tetani, and it is almost everywhere around us, except that it exists in a large number in the intestinal tract of humans and animals, and the bacillus tetani may be contained in soil, dust and feces.

The crux of the matter is the depth of the wound.

Bacillus tetani is an anaerobic bacterium, so in ordinary air, the spores of Bacillus tetani are in a dormant state due to the presence of oxygen in the air. Therefore, shallow wounds are not easy to get tetanus.

However, once the wound is deep, once the tetanus spores enter the deep wound, the anaerobic environment will revive the spores, and after the bacteria multiply, they will produce a strong neurotoxin, namely tetanospasm toxin, which will pass through the blood in the human body. spread. This is when people get tetanus.

What metal does not rust or corrode?

Inert heavy metals are not easy to rust, such as Platinum, Gold, Silver, Iridium, etc. If you’re doing crossword puzzles, try these words.

But in life, the most common and widely used material is stainless steel. There are many non-rusting metal outdoor furniture that are made of stainless steel. Common non rusting stainless steel grades are 304 and 316.



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