How to Blacken Stainless Steel?

We know how much you love to cook. But cooking isn’t all about heating the pots and pans. It requires a lot of cutting and slicing too. So you must have bought a couple of stainless knives.

Unfortunately, these things don’t stay the same all over the year. So it needs to blacken to increase its durability.

In this following discussion, you will learn about how to blacken stainless steel and keep it usable for ages.

What Is the Black Coating On Stainless Steel?

Before you blacken your knife, you must get proper information about its importance. Oxidation is connected with toxic rust on steel, and you must save your blades from it.

Surprisingly, all kinds of oxidation are not toxic or damaging to metals. Some oxidations work as a protector for the steel instead. As a result, a black coating is helpful for protecting specific steel types.

Additionally, steels are darkened for aesthetic reasons. A lot of people find blackened knives visually beautiful. It also adds stealth to the weapon.

These kinds of steel knives are very much in demand among militants as they must keep their weapons invisible and safe during unfriendly situations.

What metals can be blackened?

Other than stainless steel, the following metals can be blackened:

  • Iron
  • Cast iron
  • Regular steel
  • Ferrous materials

How To Blacken Stainless Steel Blade?

Among several methods to blacken a steel blade and protect it, the following mentioned methods are mostly used and the most effective.

Using Ferric Chloride to Blacken A Knife

A lot of knife makers use ferric chloride chemicals as a blacking method for knives. Knifemakers usually soak the steel in ferric chloride for a certain amount of time so that the blade gets darker.

The strength of the solution and the amount of time the steel is soaked in it will fix how long the blade will take to blacken completely with ferric chloride.

You will find ferric chloride at most of the knife maker stores. However, you have to handle it really sensitively as it is entirely an acidic substance. You may end up hurting your skin or even your eyes if you are careless.


You must clean the steel item with acetone first. It will remove all kinds of spots and scratches from the knife. Because of the acetone, the steel won’t get darker for the oil spots during the process.

Also, you need to neutralize the acid as you soak the steel in it. Add baking soda and rinse it well with clean water. Otherwise, it may start damaging the steel.

You may use Ferric chloride to darken stainless steel; however, the process of blackening takes more time on stainless steel than it does on carbon steel. Even you may end up damaging the knife while using the acidic chemicals on it for blackening.

Well, we would suggest you not to use this method on stainless steel when you are at home, or you have no expert guidance around you. In case any mishap happens, it can end up hurting you very badly.

By the way, you can any time buy a stainless-steel item that it already blackened.

Using Chemical to Blacken A Knife

Stainless steel, copper and copper-based alloys, zinc, powdered metals, and silver solder can all be converted using black oxide, often known as blackening. It is used to improve aesthetics, reduce light reflection, and offer a little bit of corrosion resistance.

The best level of blacking requires treating the black oxide with oil or wax. Its minimal buildup is one of the biggest advantages.


As a process of blacking, chemical blacking creates a coating by reacting the ferrous metal with the oxidizing salts that are used in the Black oxide coating. It is different from other procedures in which a layer is just put above the substrate.

Stainless and carbon steels are subjected to hot metal blacking. It is accomplished by combining sodium hydroxide with an oxidizing agent, such as sodium nitrate.

Parts will first go through several pre-treatments based on what they are made of, all of which is done in-house to get the perfect results. Chemically blackened items are sealed with wax or oil to increase their resistance further.

Using Citric Acid to Blacken a Stainless Steel

You can use citric acid for blackening. You will find it easily at your home. It is used while baking and can be found easily at a grocery shop.


First, make sure the glass you are going to use is spacious enough to hold your stainless steel item. It will allow the steel item to cover entirely in that mixture and blacken it without leaving a single spot.

Before you place the steel item in the solution, you must clean it properly first. Otherwise, the finger spots or oil residues on it will not let it blacken properly. There will remain patches that do not look good at all.

Place your stainless steel item in that solution. Now you have to wait for a bit. Soon you will find bubbles popping on its surface. It is what makes the steel item black. Finally, you have to wait until it gets the dark shade you want.

For lighter blackening, you can take it out early. But if you want it to have a dark blackening effect, you need to wait longer and let it soak in that solution.


Using Vinegar to Blacken a Stainless Steel

Among all the previous methods, vinegar is the safest option for you. it is not only safe but also the most available item for you. In fact, you may find it right now on your kitchen shelf.

Though it can darken stainless steel, you won’t get much of a darker tone, definitely not as black as carbon steel. Yet, it may work well by blackening the steel if you soak it for a long time.


First, make sure the holder you are going to use is spacious enough to hold your stainless steel item. It will allow the steel item to cover entirely in that mixture and blacken it without leaving a single spot.

The best type of vinegar for this method is white spirit vinegar. Pour it in the glass or the pot you are using for this method. Here, you need to be careful that it must not come in contact with the handle. It will have the steel part only as It can damage the handle part.

As you see bubbles on the surface, you will understand the process has begun. Now it’s your turn to wait until it gets black enough as you want it to be.

Finally, remove it from that solution when it is blackened perfectly and rinse it well. In case it has not met your blackening requirement, you can repeat the process anytime. You must rub it with baking soda, so the vinegar is neutralized, and then dry it well after washing it.

To Wrap Up

The techniques used by knifemakers involve the use of heat and other chemicals. But it is unsafe if you want to blacken your steels at home. So, you better blacken them with the easily available methods.

It may require longer to blacken them, but it is safe and easy for you and your stainless steel items.

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