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Oxidation of steel, metals (blackening)

Oxidation of steel metals (blackening) is an industrial process involving coating metal surfaces with a layer of oxides to increase their durability and aesthetics. Oxidation produces characteristic color changes on the surface of the metal, which can be of aesthetic interest. What are the advantages and disadvantages of the oxidation process? What precisely does it consist of? We write about it below! 

Oxidation of steel - what does it consist of?

Oxidizing steel, also known as blackening, produces various components for industry, such as bolts and pins, tools, jewelry, and automotive parts. Applying a thin layer of its oxides to the material gains a uniform protective coating against corrosion. Oxidizing steel involves coating the surface of the metal with a layer of iron oxides, which gives it a characteristic color from black through maroon to dark shades of gray. This process is intended to protect against corrosion and add aesthetic value to metal details. 

What are the types of oxidation of steel? 

The oxidation process can be carried out in the chemical method (cold) and the electrolytic method (hot). The chemical method involves immersing a steel component in a hot solution containing sodium hydroxide and silver nitrate. On the other hand, the electrolytic method is carried out as part of the anodic oxidation process, where special equipment is used to maintain the proper proportions of solution and temperature.

Cold and hot oxidation

  • Cold oxidation is a less demanding process that does not require high-temperature chemical solutions. You can do it yourself by cleaning the object of rust, dirt, and grease and then applying a specialized preparation. It is a popular option among hobbyists and do-it-yourselfers.
  • Hot oxidation, on the other hand, requires the use of solid chemicals applied at high temperatures. This is a more professional method, often used for industrial purposes, providing a durable and aesthetically pleasing protective coating on metal parts.

Oxidizing steel is significant, especially for components such as bolts, which need to resist corrosion. By oxidizing, steel becomes more durable and aesthetically pleasing and gains an additional protective layer. This makes bolts and other metal parts more durable and retain their properties longer.

Advantages of cold-oxidizing steel

Cold oxidation of steel has many advantages that make it a popular method of protecting metal components. 

  • One of the main advantages of this process is that you can do it yourself. Thanks to metal blackening preparations available on the market, any DIY or hobbyist can oxidize steel at home. 
  • It is unnecessary to use specialists' services, which saves money. 
  • Another advantage of cold oxidation of steel is the affordable price of the service. Preparations for blackening metals are available at different prices, allowing you to customize your choice according to your needs and budget. This makes cold steel oxidation more accessible to a wider audience.
  • In summary, cold oxidation of steel has many advantages, such as the ability to do it yourself and the affordability of the service. In addition, the black coating formed on the surface of the metal gives it a modern and elegant look. 

Advantages of hot oxidation of steel

Hot oxidation of steel ensures professional workmanship through strong chemicals and high temperatures. This process of oxidizing steel is widely used in industry to impart desired properties to steel parts and increase their durability. Here are some advantages of hot oxidizing steel:

  • Durability: Hot oxidizing steel creates a durable coating that protects the metal from corrosion and mechanical damage. The strong iron oxide layer provides long-lasting protection from the elements and prolongs the life of steel components.
  • Aesthetics: Hot-oxidizing steel gives metal parts an attractive black appearance that is durable and abrasion-resistant. This aesthetic effect is particularly desirable for knives, weapons, jewelry, and other metal items intended to be functional and beautiful.

As you can see, hot oxidation of steel has many benefits and is widely used in various industries. With professional workmanship, strong chemicals, and adequate corrosion protection - hot oxidation of steel is ideal for those looking for durable and aesthetically pleasing steel components.

Why do bolts need to be corrosion-resistant?

Bolts play an important role in maintaining the safety and proper operation of machinery, vehicles, and structures. Exposed to various atmospheric factors, such as:

  • moisture, 
  • rain, 
  • salt,  
  • chemicals.

Unfortunately, bolts without proper protection can corrode, which leads to a weakening of their structure and can consequently cause failures or accidents. To prevent corrosion, various methods are used to protect bolts, and oxidation of steel is one of the most popular. In practice - the oxide layer protects the metal from chemical reactions, prevents the formation of rust, and increases durability and resistance to external factors. Using the oxidation of steel - bolts can maintain their functionality and strength for a long time. In addition, oxidation allows bolts to have an attractive appearance, which is important for aesthetic applications such as furniture or decorations.

In which materials is oxidation applied? 

Due to its popularity and availability, the most common oxidation application is in steel. Oxidation is most commonly used in the following materials: 

  • Oxidizing stainless steel: Oxidation can be used not only on ordinary steel but also on stainless steel to make it more durable and aesthetically pleasing.
  • Oxidizing aluminum: The oxidizing process can be used on aluminum to create a durable and corrosion-resistant protective coating.
  • Blackened steel: Oxidizing steel is one of the processes that achieve a blackened effect on steel, giving it a unique appearance and protection against corrosion.
  • Oxidized metal: Oxidation is applied to other metals like copper and brass to achieve durable and aesthetic finishes.

What are the advantages of oxidizing steel?

Oxidizing steel is beneficial in terms of both durability and aesthetics and protects against corrosion. Below are the most essential benefits of oxidizing steel:


Oxidizing steel increases its durability and resistance to damage. The iron oxide coating makes steel more resistant to abrasion, scratching, and corrosion. This makes steel components, such as bolts, last longer and do not lose their properties under harsh conditions.


The blackening of steel gives the metal surface an attractive and elegant appearance. Oxidized steel can range from maroon to dark gray, allowing you to match its appearance to your specific aesthetic requirements. As a result, oxidizing steel is popular in the design of decorative items, jewelry, and other items where appearance plays a key role.

Protection against corrosion

The iron oxides formed during oxidation provide an effective barrier against moisture, chemicals and oxidizing external agents. As a result, oxidized steel retains its properties and appearance for a long time.

Blackening is a way to achieve a dark appearance on the metal

Due to its popularity, steel is often subjected to blackening to achieve the desired aesthetic effects and protect against corrosion. The blackening of steel has many applications. The dark appearance of the metal is particularly desirable for: 

  • knives, 
  • guns, 
  • gun barrels, 
  • rifles, 
  • bolts and other metal vehicle suspension components. 

Oxidation not only adds aesthetic appeal to the items but also protects against other forms of corrosion. However, it is worth remembering that the black coating on metal can be sensitive to acids and easily scratched. Therefore, the oxidation must be inspected professionally and regularly to maintain its durability and aesthetic appearance.

What are the advantages of blackening steel?

Among the recommendations for blackening steel, we can mention the following: 

  • Achieving a dark metal appearance that stands out from other surface treatments.
  • Improving the aesthetics of objects.
  • Protecting the metal surface from corrosion and other forms of damage.
  • A durable and long-lasting coating that is not too easily scratched or scuffed.

Stainless Steel vs. Carbon Steel in Oxidation 

Steel is one of the most versatile materials in various fields, from construction to the automotive industry. However, not all steel alloys are the same, especially regarding oxidation resistance. In this context, the two most commonly used types of steel are stainless steel and carbon steel. But how do they differ in terms of oxidation resistance?

Carbon steel and oxidation

Carbon steel is one of the oldest and most widely used types of steel. It is relatively cheap and easy to produce but has one major drawback: it is susceptible to oxidation. When carbon steel is exposed to oxygen and moisture, the oxidation process leads to the formation of iron oxide or rust. This rust weakens the metal and can lead to damage, which is particularly problematic in support structures and machinery.

Stainless steel, and oxidation

Unlike carbon steel, stainless steel contains additional elements such as chromium, nickel, and sometimes molybdenum, significantly increasing its oxidation resistance. The chromium in stainless steel reacts with oxygen to form a skinny but durable chromium oxide layer on the metal's surface. This layer acts as a barrier that prevents further contact between oxygen and iron, minimizing the risk of rusting.

Comparison of the two materials

Stainless steel is more resistant to oxidation than carbon steel but is also much more expensive. Therefore, the choice between the two types of steel depends on the specific application and durability requirements. In areas with crucial corrosion resistance, stainless steel is usually a better choice. Carbon steel may be sufficient in other applications where cost is more important, provided appropriate protective measures, such as anti-corrosion coatings, are applied.


In summary, oxidizing steel and metals (blackening) is an industrial process that aims to increase the durability and aesthetics of metal objects, finding applications in various industries and offering many benefits. Bolts and other metal components must be resistant to corrosion, as their durability directly impacts the safe and proper operation of machinery, vehicles, or structures. Oxidizing steel is one popular way to protect it from corrosion, so bolts can be used in various conditions, ensuring a long service life.