Patina is a film of varying green and blue shades that form on bronze or metals, whereas rust is an orange-brown color that affects blades made of steel. Both may seem like a bad thing, but Patina actually covers the material of blades with a protective layer. You can use this benefit to avoid permanent damage to the blades.
That’s the biggest difference between patina vs rust. Basically, one is good while the other is pretty bad. In this article, I’ll talk about how you can handle these conditions to keep your knives safe. Plus, I’ll share some excellent tips on how to use patina to your advantage.
Why Differentiate Between Patina and Rust?
Learning the difference between rust and patina can be life or death for your cutlery. One can cause irreversible damage to knives, while the other one may be the ultimate protective barrier. Here’s how you tell patina and rust apart.
How to Differentiate Between Rust and Patina?
Rust has an orange-brown color, and it’s an active form of rust or corrosion. This means that rust will expand across knives blades until the blades are no longer useful.
On the other hand, patina is a passive type of rust. This form of rust seals the underlying steel from elements like oxygen. As such, patina becomes an excellent method to give your knives fantastic corrosion resistance.
You can differentiate patina and rust through multiple elements like their color, what causes them, and their consequences.
Sometimes, it can be tricky to identify whether the brown or reddish color on the knives is patina or rust. If this is the case for you, I’ve found a quick and easy tip to have the definitive answer. Here’s what you gotta do:
- Add some vinegar over the rust/patina spot found on the knife. If it’s rust, it will react quickly, producing iron acetate in a few seconds.
- Vinegar is such a versatile product, and it’s super useful for restoring rusted items like chef’s knives, pocket knives, and others. In these cases, vinegar will detect rust spots easily.
Keep the vinegar bottle close because there are other uses for it!
Difference Between Patina and Rust: Side by Side Comparison
|Formation process||Exposure to an oxidizing environment. Oxidizing chemicals (Superficial layer).||Exposure to moist air.|
|Chemical composition||Ammonium sulfide Liver of Sulfur Cupric nitrate Ferric nitrate||Hydrated iron (III) Oxide (FE2O3 NH2O) Oxide Hydroxide (FEO(OH))|
|Good or Bad||Good||Bad|
|Color||Matte sandstone yellow White Red Black Deep blue Green colour||Orange-brown color|
Patina Vs Rust: Key Differences
After reading briefly about them, let’s break down the differences between patina and rust in detail.
The formation process for both rust and patina on knives differ from one another. This is one of the most significant differences to consider.
What Forms Patina? – It’s a thin layer of one or multiple colors that variously forms on different surface types. Most prominently, over knives made of metals like your regular steel kitchen knife.
Realistically, patina forms on the surface of iron or steel knives due to oxidation following exposure to atmospheric elements. Different circumstances can cause it, though oxygen, rain, and acid rain are the most common. All of this causes oxidation and patina over the blade of your knives.
Alternatively, you can form patina with a superficial layer using chemicals.
The term patina also applies to other things besides metals surface. For instance, it may refer to ancient bronzes or leather goods. More specifically, the process of high-quality leather aging. Additionally, patina can be present in wooden furniture, sheen produced by age and wear.
What Forms Rust? – The American Heritage Dictionary defines rust as various metallic coatings formed by corrosion, which is a simple yet useful definition.
Rust is a process that occurs after acidic substances like water make contact with metals like iron or steel. This exposure of the iron particles to oxygen and moisture deteriorates steel, forming rust in the process.
Even without a specific concept like the one from the American Heritage Dictionary, rust can be an everyday issue for cutlery and other items. You can see it on iron or metal knives, plants, and even patio furniture.
Pit Corrosion – The Truth Behind
At first, it may be difficult to understand how pit corrosion forms. However, there’s an easy way to explain this issue.
You see, stainless steel doesn’t oxidize when exposed to air humidity up to 70%. About 15% of chrome added to steel makes this feat possible. This chrome creates a thin chrome oxide layer that seals the steel, preventing exposure to air and rust.
When that chrome oxide layer gets damaged, a new one forms. This is standard procedure in most cases.
But, if the steel knives remain exposed to a moist or wet environment, the new chrome oxide layer won’t form. Here, even the smallest drop of water will create pit corrosion without a new chrome oxide layer.
Strong collisions or chemicals can damage the chrome oxide layer. This is something that can happen in the following scenarios:
- Not cleaning the knives after using them. Knives get exposed to food acids.
- Washing the knives but not drying them afterward. Knives get exposed to moisture.
- Putting your knives in the dishwasher may expose them to water & may take strong impacts against other items.
- Leaving the knives in the sink, soaking in water.
- Not storing your hunting or pocket knife at a moisture-free location.
All of these events take a toll on the chromoxide layer. Thus, rust forms.
The patina and rust exist due to two different chemical processes.
Chemical Formula of Patina – Different chemical compounds create patina. These include oxides, sulfides, carbonates, or sulfates. Other elements like carbon dioxide or sulfur-bearing compounds could also play a role.
Chemical Formula of Rust – Rust is a rather broad term that refers to a series of iron oxides. Normally, these are red oxides. The formation of rust on knives comes from the reaction caused by the clash of iron with oxygen via air or water moisture.
The chemical formula is Fe2O3. People know this formula as iron oxide or ferric oxide.
Good or Bad
While comparing rust vs patina, one of the first things that come to mind is why the reddish-brown rust is bad, but the green rust is good. Let’s go over this briefly to clear up confusion.
Is Patina Good?
Though it is a form of corrosion, green patina protects the knife from corrosion or rust. This is why many people applied patina to their cutlery or antiques intentionally. Even a thin layer of patina coating allows cutlery like a carbon steel knife to withstand rust.
You won’t have to worry about any form of pitting corrosion, corroded copper rust, brass corrosion, and more. Patina prevents all of that and keeps the knives safe.
Tip: Keep in mind that while brass and copper alloys don’t rust, they do corrode. So, patina can also be helpful to copper. Patina is also excellent over ancient bronzes. In fact, bronze patina can be a form of art found in jewelry and architecture.
Why Is Rust Bad?
Besides making the surface of cutlery not aesthetically appealing, rust is a form of corrosion that adds impurities to the food. Plus, rust isn’t water-soluble. Without treating it properly, the “reddish-brown color” will expand and render the knives unusable.
But rust doesn’t only damage metal knives. In many cases, the plants caused the continuous spreading of a parasitic fungus called rust. This is a reddish-brown fungus that wind-driven spray can make unstoppable.
Color on Knives
Though it may not be easy to tell rust and patina apart at first, their colors are a giveaway. Color is easily the main difference, as it shows that they’re not the same thing. This is how you differentiate the two on any surface made of metal, copper, bronze, iron, or steel.
What Color is Patina?
Often called green rust or blue green copper rust, the most popular color for patina coating are green color and blue. But there are more than just that. Here’s a list of patina colors found on knives blades with a surface made of copper, iron, or steel, among others.
- Matte sandstone yellow
- Deep blue
- Green rust / Green colour
Rust’s Color is a Shade of Orange-Brown
Also known as a reddish-brown color, rust is actually more of an orange-brown shade on knives. It resembles iron oxide. If you notice this color on your iron or steel knife instead of the green color, act quickly to prevent rust.
If you need examples, look at old bicycle chains or patio furniture. A bicycle chain left on the open for too long will cause it to rust quickly. The same goes for patio furniture made of metal.
Frequently Asked Questions
1. How can I patina metal quickly?
To add patina on metal, you’ll need ammonia, some salt, paper towels, and a container with a flat-type bottom. Plus, copper wires will be necessary to hold the metals. Plug some holes in the container and attach the wires in a way that’ll let you hang the metals.
Put some paper towels in the bottom of the container, clean the metal piece with alcohol, and hang it over the copper wires. Spray the piece with ammonia, and cover it with salt afterward.
Follow up by spraying more ammonia. Then pour some ammonia over the paper towels and add salt as well. Close the container and let it rest for about 12 or 24 hours.
Tip: Wear gloves and perform this procedure at an outside location.
2. Is patina toxic?
It’s easy to assume that patina is a toxic form of deteriorated state. But that’s only in some cases. For example, coating copper with ammonia allows the cutlery surface to gain blue and green colors.
Since blue-green copper rust has hydroxides and chlorides, some consider this type of patina dangerous if inhaled. Plus, it’ll damage iron or steel permanently.
Then you have something like bronze patina, which simply looks fantastic.
3. Does silver rust in water?
Atmospheric elements like moisture may not damage silver, but it may not be as aesthetically appealing as well. This is because moisture causes silver to go through oxidation, darkening its surface during the rust chemical process.
4. How to stop knives from rusting in the dishwasher?
Keep your carbon steel blade and other cutlery safe from iron oxide, corrosion and rust by doing the following:
- Rinse the iron or steel utensils beforehand.
- After use, wash metal cutlery immediately. This helps prevent the oxidation process.
- Don’t overuse detergents. Chemical compounds, formulas, or a similar substance may hurt cutlery materials more than you’d expect.
- Get the cutlery out of the dishwasher quickly. Leaving metals, iron, and similar materials exposed to moisture may tarnish them or cause discoloration. Keep in mind that tarnish isn’t the same as patina.
- Using a set of covers works for protecting the knives.
5. How to fight off rust fungus on plants?
To fight off the parasitic fungus called rust in plants, you have to use weekly dust of sulfur. It’s a quick solution that will cause the reddish-brown fungus that plants caused to go away. This way, wind-driven spray won’t expand it.
6. How to remove rust spots from pocket knives?
You can prevent corrosion by soaking the carbon steel in white vinegar, baking soda, and lemon juice.
After taking good care of your knives, a set of covers works perfectly to keep metal blades safe.
Recommended tool to prevent rust on knives: Best Knife Oil for Rust-Free Blades
Rust is a form of corrosion that affects the metal surface, including blades of chef’s knives or pocket knives. Unlike patina, rust isn’t a protective covering. It can damage a pocket knife featuring a carbon steel blade quickly if you leave it exposed. Avoid this issue by keeping your knives away from moisture.
To Sum Up
Once you take a closer look at the patina vs rust comparison, it’s clear why they’re not the same thing. If you’re dealing with rusted utensils, acting quickly is a must. With patina, you could use that to your advantage. Metal items will resist corrosion more efficiently, and they will also look better.