Rusting can cause an array of problems. They range from producing cracks and holes in metals to reducing metals’ magnetic properties and electrical or thermal conductivity. Although rust is non-toxic, its presence in infrastructures can jeopardize our safety. It affects things such as bridges and cars. Since it is a natural phenomenon, all metals containing iron must be regularly checked to avoid any safety hazards.
|Materials we’ll take a closer look at|
What causes metal to rust?
Rusting is the most common example of metal corrosion, and it happens to materials made up of or containing iron. When the iron comes in contact with air and water, an electrochemical reaction occurs. An oxide forms: iron oxide in its hydrated form.
Yes, it is just the common name for iron oxide. Depending on the type of iron oxide formed, the color may vary from yellow to green. It can also be a mix of these colors. The most common one we see is red rust. It is iron oxide trihydrate or hydrated ferric oxide with a chemical formula of Fe2O3•H2O.
In a nutshell, this is what happens:
iron + oxygen + water → iron oxide trihydrate
This chemical reaction won’t happen without moisture or water. It’s important to safeguard the metal from exposure to moist or wet environments. Water facilitates the transfer of electrons between iron and the environment, which is the oxidation of iron. Let me discuss it briefly below:
- When exposed to a strong oxidizing agent such as oxygen, the iron in the metal 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. The oxygen gets dissolved in the water, forming 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 chemical 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. This is because more oxidizing agents are available to attack the iron, corroding the metal faster.
Other metals also undergo this type of corrosion. The resulting oxides cannot be classified as rust simply because they are not iron oxides. For example, silver reacts with sulfur. The oxide called silver sulfide is formed, commonly known as silver tarnish.
Brass is an alloy of copper and zinc, with the former usually being the main component. Depending on the proportions of copper and zinc, the color may change from bright gold up to reddish-gold or silver. Other elements may also be added depending on what is needed, non-metal or metal.
Copper is extremely ductile and has a high thermal and electrical conductivity, but it is soft and malleable by itself. The addition of zinc improves the strength and flexibility of the brass. The resulting alloy has a low melting point and high workability and durability. It’s the perfect material for musical instruments and decorative items. It’s also great for plumbing and locks.
Does brass rust?
Brass does not contain iron unless it is an added component for certain applications. It is usually added at a very low concentration of iron, so it isn’t very important. Therefore, it does not rust.
However, brass does corrode and oxidize! The resulting oxide isn’t iron oxide, so you cannot classify it as rust. It’s more suitable to call it tarnish.
Here’s one example of how it corrodes: Selective leaching.
When the zinc in brass leaches off, it is called dezincification. And when zinc is lost, the alloy weakens because zinc is the one that contributes to the durability/strength. Copper is left behind. If copper is the one that leaches off, it’s called decuprification. Either way, the structural integrity of brass will be compromised.
Dezincification is more common since zinc is more reactive than copper. Once this happens, pink or reddish discoloration on brass appears. Exposure to moisture or water will also quicken this type of corrosion since the zinc will oxidize faster. In musical instruments, the dezincification occurs in areas where the instruments were held. It’s caused by sweat as the source of moisture. Musicians call this phenomenon “red rot.”
What is the blue-green layer that forms on it?
Although this phenomenon is also caused by oxidation, the blue-green layer you see on brass is not a sign of corrosion! It’s called patina, a naturally-occurring film layer on most metals. The patina is not detrimental to the alloy—it may become a shield against air and moisture. Many people even consider this color change attractive on brass. Some accelerate the oxidizing process by applying solutions for an “aged/vintage look.”
How to remove “rust” from brass
The “rust” that people see in bronze isn’t rust. Selective leaching doesn’t happen quickly. The weakening of brass accompanies it, so it’s most probably just patina that you’re seeing. Patina can be easily removed by scrubbing with hot, soapy water. But if that doesn’t work well, it’s probably mild dezincification you’re dealing with. Try using an abrasive slurry like baking soda and lemon/vinegar paste. Leave it on for 5-10 minutes, and then rub it in for a few seconds. Alternatively, you can also use commercial abrasive polish such as calcium carbonate silver polish. Rinse it properly and coat it with a bit of mineral oil. Lastly, use a microfiber cloth to buff the brass and bring back its shine. It’s like how wide belt sanders give wood the perfect, smooth finish.
To avoid patina formation or tarnishing, you should regularly keep it clean and dust-free. Avoid exposing it to moisture, especially with salts or acids. Sweat is a no-no. Also, any commercial polish used on brass must be rinsed off properly. A coating must be applied to protect the surface from further tarnishing.
Severe dezincification that extends deeply into the alloy is hard to solve, and you might end up discarding the item in the end.
Zinc is mostly used to galvanize steel, applied as a coating that’s metallurgically bonded to the steel. It protects it from corrosion like oxidation or rusting. Zinc acts as a sacrificial metal, reacting with oxygen to form a zinc oxide layer that prevents rusting or the formation of iron oxide.
By itself, zinc is pretty weak and brittle. It has low to moderate tensile strength and conductivity. The resulting alloy usually has high impact strength when alloyed with other metals. It also has ductility and is more corrosion-resistant.
Zinc itself doesn’t rust, but the process may occur if alloyed with iron or ferroalloys. Also, suppose the zinc layer of galvanized steel is compromised. It may occur since the underlying material that contains iron will be exposed to air and water.
Titanium is a strong, lustrous, and corrosion-resistant metal. Its high corrosion resistance is due to its ability to form titanium dioxide upon oxidation. Its strong oxide layer protects the titanium metal underneath from corrosion caused by most acids and saltwater. Furthermore, other salts that would usually speed up the corrosion of some metals inhibits the corrosion of titanium. Like tungsten, titanium is one of the most durable natural metals. Despite being resistant to most corrosion-like oxidation, titanium isn’t immune to pitting and saltwater corrosion at elevated temperatures.
Titanium itself doesn’t rust. The commercially available forms of titanium are usually alloys. If iron is one of the alloy’s components, it can happen.
If you’re looking for a tool to cut this strong metal, oxy torches or plasma cutters can still do the job. But if you’re dealing with metals that are not as tough as titanium or tungsten, these engine-driven welders will be perfect for you.
Tin will not rust, if not alloyed with iron. This soft, pliable silvery-white metal is used for electroplating or coating steel and other types. It can also be used as an alloy component to prevent corrosion and rusting. It is why it is used to coat metal used for food storage. It does not rust or corrode at room temperatures. Tin can still corrode at elevated temperatures, react with water and oxygen, and form oxides.
Pure tin is commonly mistaken for tin-coated steel. Thus, it is called tin. The latter can rust if the tin coating is compromised.
How to remove it from tin
Rust can readily form when the steel underneath the tin coating is exposed to water and air. To remove it, you can also use abrasive tools. It’s just like removing patina or tarnishes. The most common method is to rub it off with fine steel wool and rinse it with warm soap and water.
Although effective in removing it, abrasive methods can further damage the tin coating. A gentler approach is using lemon juice/vinegar and baking soda paste. Apply the paste to the affected areas, and rub it in for a few moments. Leave it on for a few minutes. Scrub off the paste gently with a sponge, and see if it has softened or come out. If not, repeat the soaking process. Rinse the item with warm soapy water.
Sterling silver is an alloy of silver and another metal, usually copper. The standard purity of sterling silver is 92.5% by weight of silver, hence the name “925 sterling silver” for jewelry. The other metal component constitutes only 7.5% by weight. This proportion retains the silvery color of the alloy.
Sterling silver does not rust, but it is not immune to other forms of corrosion.
The addition of copper makes sterling silver more susceptible to oxidation and corrosion. It’s because copper is a more reactive metal of the two. This is why sterling silver tarnishes more easily than fine or pure silver. But the addition of copper is necessary for silver to be workable and turned into something of use. Fine silver is 99.9% pure silver. It is too soft to be used in making tools or jewelry. The addition of copper increases its durability and hardness.
Like in brass musical instruments, sterling silver jewelry will tarnish when it gets in contact with moisture like our sweat. The presence of salt in our sweat speeds up the process of oxidation. Tarnish is not necessarily something to panic about because you can easily have it cleaned/removed. Further neglect of the item is not the right way to go.
When tarnish is not cleaned, and the item is not protected against exposure to air and moisture, oxidation will damage the metal. It makes it more vulnerable to other forms of corrosion, such as pitting.
Lead is a bluish-white to silvery-grey metal that is soft. It is highly malleable and ductile. Although it is a poor conductor of heat and electricity, it is resistant to corrosion. Lead has been used for years to make pipes and insecticides. It was also once used in paint. It has been banned due to leaching and its detrimental effect on health. Lead is widely used in roofing or glass windows. You’ll also find it in car batteries and pigments.
Lead does not rust, but tarnishing is a common problem with this material. When freshly cut, it is a lustrous silver with a bluish tinge. But when exposed to moist air, it tarnishes to a dull silver-grey color. It is the color that we commonly see.
Coating metals to increase their corrosion resistance or retain their luster has been widely practiced. It’s important in galvanizing steel and lacquer-coating brass. Powder coating also has the same purpose. It is done with materials such as steel as a resilient, protective layer. The resulting powder-coated steel has improved corrosion resistance and durability, extending its lifespan.
Powder coating is one of the processes in manufacturing fuel transfer tanks, which increases the quality of the tank’s finish. Some car parts like valve covers are powder coated for more protection to avoid damage to idle air control valves.
Powder coating is a dry coating process, unlike galvanization. Zinc is applied as a liquid for adhesion purposes. Steel is hot-dipped in molten zinc. In contrast, powder coating is applied dry and adhered to the steel with the help of electrostatics. One of the many advantages of powder coating is it can come in different colors and chemical compounds. Powder coating materials can either be thermoplastics or thermosets.
Screws are often made from zinc because of their advantageous properties.
- These coating materials are usually plastic polymers that are soft when heated and harden upon cooling.
- The coating material can be altered after alterations and removed even after setting on the substrate/steel.
- It is more ductile and has better chemical resistance.
- these coating materials form strong cross-links within their molecular structure when cured. Coating material can’t be altered post-curing.
- Cross-linking in molecules gives stability even at high temperatures. It’s ideal for high-temperature applications like waste oil heaters.
Powder coating is resistant to chipping and damage, but it is not immune to damage forever. Although it can last up to 20 years, powder coating can slowly deteriorate. When enough damage/wear is accumulated, the coating will be compromised. The steel underneath will rust upon exposure to moist air.
How to remove the stains
One of the hassles of rust is when it gets onto clothing or other fabrics. It’s a stubborn stain and will not disappear with the usual laundering tricks. It sticks to the fabric even after using bleach. But here’s the good news: Fabrics can still be saved using lemon juice, salt, and baking soda!
The first thing that I tried was the salt and lemon combo. If the fabric isn’t colorfast, test the lemon juice on it first to check if any bleaching or fading will occur. If there isn’t any, then you can proceed.
- Put salt on the stained area, and then wet the salted areas with lemon juice. Make sure not to miss any stains!
- Pick a sunny spot outside, and lay down the fabric. The stained area should be facing the sun. Let the sun do its work.
- Once the fabric is dry, wash the garment as usual and use a heavy-duty laundry detergent once the fabric is dry.
Try the baking soda and hydrogen peroxide combo next if this technique doesn’t work! This may cause fading, so only on white and colorfast fabrics.
- In a bowl, add 1-2 spoonfuls. It depends on how much you think you’ll need to cover the stain—of baking soda.
- Add a few drops of hydrogen peroxide and mix periodically until you get a paste consistency.
- Apply this paste onto the stained areas, and let it sit for 30-60 minutes. Rinse the fabric with water.
- Launder the fabric using a heavy-duty detergent.
It’s best to air dry the fabric first if you’re not sure whether you’ve taken out all the stains. The blast of hot air in dryers may set the stain onto the fabric. But if you’re sure that you got all stains out, feel free to use the dryer!
If both home remedies didn’t work, try using a commercially available remover. Make sure that the fabric is colorfast, or else the dye will be washed away. Choose a remover that applies to fabrics. All removers come with their own set of precautions and instructions, so read and follow them carefully.
Almost all removers follow the same procedure: apply it to the stained area, let it sit for a few minutes, Then rinse with water. After that, you can launder the fabric as usual.
Does Rustoleum stop the damage?
If you’re no stranger to automobile work, you’re probably familiar with protectors and converting primers. There are also removers out there. In my experience, Rust-Oleum products work best on metal that hasn’t rusted that much yet. As I’ve always mentioned, prevention is better than cure. These products work best on clean surfaces that have little to no rust.
Applying inhibitors on metal already heavily damaged won’t successfully stop it from continuing. Applying thick coats of Rustoleum on moderately or heavily damaged metal might slow down the process. You’ll see some bubbles or cracks soon enough, and spots will appear sooner rather than later.
When it comes to stopping rusting, you might need two to three products: A metal primer or reformer, a protector, and a top coating or paint. Results may vary depending on the extent of the damage. You’ll still need to remove the existing rust before applying all coats.
In all instructions for various metal primers and inhibitors, it is recommended that you remove a significant amount of rust first. It will let you achieve a smooth, clean surface. Primers or converting primers are usually applied first to ready the surface to adhesion further coatings of other protectors. These primers usually include ingredients that bond with the rust or turn the surface of the metal into a waterproof, paintable surface. Once the primer coat is set, another coating is usually applied. It will act as a protection layer.
Yes, these products may stop it from worsening. It doesn’t work like magic, wherein one coat or spray will magically melt all rust and stop it from reoccurring. It’s more of a preventive measure rather than a cure. You’ll have to remove existing rust and clean the metal. Prime the surface, and apply a protective coat.
Maybe you don’t want to go to such lengths and extra cost. Make sure any vulnerable item is kept away from moist or wet environments. One trick may be to get a dehumidifier. Clean items made up of metal regularly to avoid tarnishing. Suppose you notice your home frequently gathering dust. I suggest looking into UV light sanitizers for your HVAC and furnace systems. It avoids multiple exposures of your tool to water due to frequent cleaning.
Lastly, store all susceptible items in areas with proper temperature and humidity. 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. We also have many articles on topics like gauge wire and other things.
Brass is a copper and Zinc alloy, which corrodes when submerged in water. The zinc portion in the alloy is lost rather quickly, which puts the alloy’s structure at risk. As the brass undergoes dezincification, it tarnishes. As a result, a green-blue layer is formed. It is called Patina.
Zinc plated fittings and fixtures aren’t suitable for long-term outdoor use. They’re deemed corrosion-resistant. However, long-term exposure to high humidity and coastal environments speeds up corrosion.
No, zinc isn’t better than stainless steel. Even though zinc alloys are strong, stainless steel has higher strength and corrosion resistance. From a price point, Zinc alloys are relatively cheaper to purchase.
Zinc itself doesn’t rust because it doesn’t contain any iron. If it’s mixed with any iron or ferroalloys, it’s bound to undergo rusting.
Yes, titanium forms a layer of titanium oxide when exposed to chlorine at high temperatures.
No, the 100% sterling silver doesn’t rust. However, it is prone to corrosion. Pure silver doesn’t corrode or tarnish. But the other metals added to increase their strength and durability causes copper to tarnish.