Rust can negatively affect various characteristics of a metal or product. It can reduce the product’s lifespan and produce holes and cracks in metals. It reduces magnetic properties and decreases its electrical and thermal conductivity. Those are just some of the consequences of rust. Furthermore, it can also be bad for our health and the environment. It can jeopardize our safety due to the degradation of metals in infrastructures like pipes and power supplies. Bridges and buildings can also be affected.
Image source: ThoughtCo
What causes it?
Rust is another name for the chemical called iron oxide in its hydrated form. We commonly see it as the reddish-brown or yellowish-brown coating/flaky substance on iron or steel. It is one of the most common examples of corrosion. It happens with materials/metal made up of or containing iron or iron alloys. This phenomenon results from electrochemical reactions such as oxidation.
When the surface is exposed to moist air or wet environments, it reacts with oxygen gas in the presence of water. It forms an oxide layer, rust. Depending on the chemical composition of the oxide, its color may vary from yellow or red. It can also be brown or orange. You’ll also find it in a green form and a mix of these colors. The most common one is the red type, which is iron oxide trihydrate or hydrated ferric oxide. It has a chemical formula of Fe2O3•H2O. In a nutshell, this is what happens:
iron + oxygen + water → iron oxide trihydrate
Water is necessary for this reaction to occur, facilitating the transfer of electrons. Feeling confused? Let me delve a bit into the chemical reaction above. I’ll be brief to prevent you from napping!
- When exposed to a strong oxidizing agent such as oxygen, the iron readily gives up its electrons. It goes into the aqueous solution as a cation.
Fe → Fe2+ + 2e–
Balanced equation: 2Fe → 2Fe2+ + 4e–
- The oxygen and water react with the surface of the metal, and the oxygen gets dissolved in the water. It forms hydroxide ions.
O2 + 2H2O + 4e– → 4OH–
- And then, the iron ion and the hydroxide ion react to form iron hydroxide.
2Fe2+ + 4OH– → 2Fe(OH)2
- Lastly, the iron hydroxide reacts with oxygen to form red rust.
This whole electrochemical reaction is summarized in the image below. The red brick represents the rust formed.
Image source: Spennemann, D.H.R. from Research Gate
The process is sped up when the metal is exposed to better electrolytes, such as saltwater and acidic solutions/environments. It is because more available oxidizing agents can attack the iron, corroding the metal faster.
Now, let’s face the other questions that are related:
Do all metals rust? If not, what are the types that do? Does acetone remove it? What can you do to prevent it from happening? Does corrosion manifest the same for all types? Or are there different types of corrosion?
Types of metal
There are various types, some of which are prone to oxidation and corrosion. Others are not.
Noble metals are also called precious metals. They have high resistance to oxidation and corrosion, even in moist air and high temperatures. Because of these properties, they are very expensive and are widely used in making jewelry. Here are some examples:
Other transition metals can also resist oxidation and corrosion despite not being considered noble metals. Some examples are:
In contrast to noble metals, these are prone to oxidation and corrosion. Here are some examples:
An alloy combines metal and another element, either metal or non-metal.
Humans found a way to turn metals usually easily corroded into something resistant to oxidization/corrosion. It’s done by mixing them with other metals or elements. Examples of such corrosion-resistant alloys are:
- Stainless steel
However, not all alloys are made to resist rusting or corrosion. Here are some examples of alloys predominantly made up of base metals. Thus, they are also considered to be base metals.
- Brass – an alloy of copper and zinc
- Bronze – is an alloy of copper and tin. Metals like aluminum and manganese are examples, as are nickel and zinc. Non-metals like arsenic & phosphorus are often added. Silicon can be added as well.
Although many metals mentioned above can corrode through oxidation, bear in mind that not all oxidation processes produce rust. For example, silver tarnish is also an example of corrosion that happens due to oxidation. But for now, we’ll limit our discussion to rusting.
As mentioned earlier, it forms through the oxidation of iron. It can only occur in iron and metals that contain it, such as iron alloys.
These alloys have iron as their most predominant component. Due to the abundance of iron, these alloys can rust. Most of them are steels containing carbon as the major non-metal alloying element. They may also contain small amounts of silicon and phosphorus. Sulfur and oxygen may also be present. Depending on the type of steel, the ratio or percentage of elements of their composition may differ.
Here are some examples of these alloys:
- Carbon steel
- Stainless steel
- Silicon steel
- Tool steel
- Bulat steel
- Damascus steel
- Crucible steel
- HSLA steel
- Maraging steel
- Wootz steel
- Anthracite iron
- Cast iron
- Pig iron
- Wrought iron
- Ferroalloys (alloys with names starting in “Ferro-” such as ferroboron & ferrochrome)
Bronze is an alloy traditionally composed of copper and tin but nowadays is made with the addition of other metals. Some of those include aluminum and zinc. Non-metals like phosphorus and silicon can be added. This alloy has been widely used to build sculptures, tools, weapons, and bells for millennia.
Does bronze rust?
Since bronze does not have iron in it, it will not rust. It is also much more resistant to corrosion and harder than pure iron and copper, thanks to alloying copper with tin. Although bronze does not rust and is wear- and corrosion-resistant, this does not mean that it can never be corroded.
A bronze disease is a form of corrosion that affects bronze, manifesting as a green fuzz. People thought it was caused by bacteria (hence the term “disease”). It is caused by a series of complex chemical reactions involving the chlorides of the copper of the bronze and water. These chemical reactions are still not fully understood. What’s currently known is that the cuprous chloride in the bronze reacts with water. It creates hydrochloric acid that damages the bronze. It will then react with copper. It would take tens of years before this happens to bronze, but it can be sped up if the environment favors it.
Bronze disease in ancient coin
Image source: Joukowsky Institute – Brown University
However, do not confuse a layer of green patina with bronze disease! Patina is not destructive to bronze and may even protect it from further exposure to moisture. Over time, a layer of protective brown patina naturally forms on the bronze’s surface through oxidation. As more time passes, the patina becomes green.
Green patina on a bronze watch
Image source: Fratello Watches
Nickel is one of the most abundant elements here on earth. It is widely used for its properties as a good heat and electricity conductor and its high heat and corrosion resistance. This silvery-white metal does not rust since it is pure with no iron.
Due to these wonderful properties of nickel, it is alloyed with many different metals to increase rust resistance. This material is beneficial in industrial processes, especially water. It’s great because it won’t easily oxidize or rust. An example is how nickel alloys are used in making fuel tanks for heat and corrosion resistance.
Image source: Nornickel
Cast iron is an iron-carbon alloy, and it will rust. You might be wondering why then it is famous for cooking. It is because it has a high volumetric heat capacity. When heated, it stays hot for a longer time than other pan materials.
Cast iron skillets have a protective layer of carbonized oil against rusting. However, this coating can be chipped away through time and repetitive use. Making sure that your pan or skillet is not left to soak and is not stored in a moist environment is your best bet in preventing it. If your pan gets rust, you can remove it through vinegar soak or scrub it all off using fine steel wool.
Image source: Stephanie Staton – Hobby Farms
Chrome is mostly used for electroplating, done to lengthen the lifespan of metals or plastics. Chromium is a transition metal that is steely grey and lustrous. It’s also hard and brittle. It acts as a protective layer against corrosion. Thus, chrome does not rust.
Chrome plating involves the application of chromium onto the surface of an object as a finishing process. The layer of chromium is applied via electroplating, using an electrical charge. It is applied to a solution of chromium anhydride. It triggers a chemical reaction, and the chromium deposits itself onto the surface of the submerged object. This results in a silvery chrome layer that protects the underlying surface from corrosion readily. It’s because chrome is impermeable to oxygen. Thereby, it prevents oxidation.
However, rusting can occur if the chrome layer is compromised and the underlying material contains iron. Without the chrome plating, the layer underneath will come in contact with moisture and oxygen. It’s the perfect recipe for deterioration.
Image source: Alchemist-hp
Despite being brittle, tungsten is still one of the most durable elements. It has the highest tensile strength and melting point among natural metals. These characteristics make tungsten favored by jewelry makers, producing strong rings that can last for years. Its hardness and high-temperature resistance are great features. Because of the durability of tungsten, it is used to alloy with other metals for added strength and corrosion resistance. Although highly durable, it can still be cut by plasma cutters and polished by diamond wheels in some forms.
Tungsten does not contain iron, so it does not rust. However, pure tungsten does oxidize in the air. It develops a colorful tarnish or patina.
On the other hand, tungsten carbide with nickel binder does not readily oxidize and tarnish. One exception is at very high temperatures (around 1100 K above). This type of tungsten alloy is widely used for high-quality jewelry that doesn’t stain around the finger and lasts long.
It’s a picture of a tungsten cube of high purity alongside tungsten rods with evaporated crystals and colorful tarnish.
Image source: Alchemist-hp
It can rust since it is an iron alloy. Famous for its watery light and dark pattern, Damascus steel has been valued for years since the ancient period. It was used to forge the blades and weapons of warriors. It was originally cast from wootz, another type from India. It was made by melting iron and steel together with charcoal and using Sorel metal as a raw material.
The mining region in India where the wootz came from changed during the 19th century. It started bringing in impurities and thus changing the ingots for making Damascus steel. Due to these impurities, the original manufacturer of wootz Damascus steel was never replicated again.
Since its composition was shed to light and the truth about the significance of wootz ingots, it led to the successful reproduction of Damascus steel. However, it was manufactured differently. The damask pattern of the original steel was copied onto the new ones through layering iron and steel. It forged the two together by hammering at high temperatures, forming a welded bond. After multiple layers of forge welding, the watery pattern is replicated.
This synthetic gemstone rivals the beauty of diamonds. It is made from melting zirconium oxide powder and stabilizers like magnesium and calcium. Then crystals will start to form and stabilize upon removal from heat. The cubic zirconia crystals are then cut and polished. The resulting pieces sparkle like diamonds but usually have more “colors” than the natural gem.
Notice how there is no iron whatsoever introduced in making cubic zirconia. Thus, the crystal itself does not rust. If you’re thinking about jewelry, the metal that holds the cubic zirconia may. It depends on what type it is.
Image source: Essilux
Rhodium is commonly used for plating material, giving a protective coat that shields the underlying material from scratches. It shares that feature with chrome. Like how wide belt sanders can give wood a beautiful finish, rhodium plating gives jewelry a strong shine. It reflects up to 80% of light and smoothens chips and scratches.
This noble metal is one of the most expensive ones, with its pure form being even more costly than gold. It is silvery-white. It’s also hard and chemically inert transition metal. It is highly corrosion-resistant and doesn’t rust. These great properties are used as an alloying agent to form furnace coils, electrodes, laboratory apparatus, etc. It has a high melting point and is brittle, so it is widely used as an alloying agent and electroplating material.
Although the metal itself is corrosion-resistant, it can wear off over time. That is if the rhodium coating on the material is thin. If the underlying material contains iron, the jewelry or equipment will rust.
Before and after pictures of rhodium plating on jewelry
Image source: Mark Lloyd Jewellery
Chromoly will rust since it is an iron alloy but not as readily as other steel alloys containing iron. Two of its major alloying elements are chromium and molybdenum. It is why it is named “Chromoly.” These contribute to the corrosion resistance of Chromoly steel, increasing its hardness and melting point. To protect this alloy steel, it is treated with coatings. You’ll mostly find this in bicycle tubing or frame because it is more lightweight than other steel frames. Its high melting point can be used in making furnace equipment, such as waste oil heaters.
Sheet metal is metal processed into thin, flat pieces below 6mm. Depending on the material, these can be easily cut by engine-driven welders. It makes it may involve shearing and punching. It will also involve cutting and folding steel, among many other processes.
Regular steel is an alloy of carbon and iron, which will readily rust. With that being said, ones that do not rust are commonly made up of galvanized or stainless steel. Both have corrosion and rust-resistant properties. One example is stainless steel in car parts, such as idle air control valves. In contrast, galvanized steel is commonly used for roofing materials. Galvanized steel is made by coating regular steel or iron with a protective zinc coating. It’s done to shield the underlying steel from oxidation and corrosion. Once this layer is degraded, the steel underneath will degrade.
Image source: Thomas
Most people confuse galvanized steel with Galvalume. Both are coatings applied to metals to protect them from corrosion and oxidation, but these two are different things.
Galvalume is an alloy invented and introduced by Bethlehem Steel in the market in 1972. This alloy coating contains zinc, aluminum, and silicon. The combination of zinc and aluminum enhances its corrosion and heat resistance. Galvalume is widely used in roofing materials, and it lasts longer than galvanized options. It is made by hot-dipping the carbon steel base sheet with aluminum and zinc alloy. It’s done until it reaches the right percentage of alloys.
Unpainted Galvalume roof
Image source: Construction Magazine
Does acetone remove rust?
If you fail to safeguard your tools or jewelry against rusting, you can easily remove it with acetone! It is one of the easiest fixes for various surfaces. You can do it on your own without needing any special equipment. All it takes is to let the item sit in the acetone for a few hours until the affected area chips away and then scrub off the remaining stuff. If submerging the item in acetone is not applicable, you can douse a scouring pad with acetone and use it to scrub it off. Just remember to oil your equipment afterward to protect it from further oxidation.
Bear in mind that acetone can also damage the paint. You’ll have to look for other remedies to remove rust for equipment marked with paint, such as precision tools. Acetone may react with the metal or coating and produce toxic fumes. Be careful and choose which can be exposed to acetone.
Other methods to remove it include mechanical means by using a fiber wheel/abrasive buff wheel attached to a rotary tool. You can also use chemical removal with safe options like WD-40 Rust Remover and POR-15.
How to prevent it
Prevention is better than cure, as one might say. Maybe buying rust-resistant materials is not an option for you. You’ll have to care for our jewelry equipment to avoid rusting properly. First and foremost, avoid exposing it to moist or wet environments. Suppose you notice your home frequently gathering dust. I suggest looking into UV light sanitizers for your HVAC and furnace systems. It’ll help avoid multiple exposures of your tool to water due to frequent cleaning.
Also, it’s important to oil your tools regularly to prevent rusting. Oil protects the surface of your equipment from getting in contact with moisture, thereby avoiding oxidation. I always oil my engine-driven welder after cleaning its parts to ensure it won’t rust.
It is also important to store your equipment in proper temperature and humidity areas. If you noticed that your central home AC is not blowing cold air, you should resolve it quickly. Hot and humid areas do not bode well with avoiding rust. Our two most popular articles include this one on oxy torches and this one on gauge wire.
Copper doesn’t typically need rust when exposed to water. But if the water is turbulent and the copper is exposed to it for an extended period, it may begin to corrode. Over time, the copper forms a green film called patina on its surface.
When exposed to air, copper forms a protective layer of blue-green patina. The patina layer then prevents the metal from further corrosion by inhibiting the metal atoms from reacting.
Cast iron is highly susceptible to rusting. If left without any protective layer, rust begins to form on the surface within minutes. Therefore, cast iron pans are often seasoned or coated with carbonized oil to slow down the rusting process.
Since the object’s exposure to water causes rust, you need to ensure that the cast iron is not soaked in water. And even when you have washed the cast iron, make sure it’s patted completely dry. Then, leave it on the burner for a few minutes to remove any moisture. Lastly, don’t forget to season the cast iron with oil now and then.
Damascus steel is celebrated for its luster and beauty. But since it is made of high carbon steel, it’s more prone to rusting. Therefore, you’ve to be extra careful when cleaning or treating the steel.