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Black Oxide

Black Oxide

Today industrial parts manufacturers sometimes perform surface treatments to change the exterior of metal components during the finishing process. Designers may obtain desired properties in this way. One popular variety of surface treatment, conversion coating, depends upon the use of electricity and/or chemical reactions to create desired modifications on metal surfaces.

For example, the process of black oxide coating transforms the exteriors of alloys of stainless steel, steel, and ferrous metals by enhancing resistance to corrosion. It also causes color changes, ultimately blackening the metal surface. Specialized coatings permit the use generation of protective black oxides on copper and zinc alloy exteriors, too.

The Black Oxide Process

The black oxide process occurs because a chemical reaction ensues between the surface of the metal part and materials used in the coating. The metal in the part reacts with chemicals used during the surface treatment to create a hard, magnetic black iron oxide shell over ferrous alloys. This thin protective layer results from a chemical reaction which darkens the appearance of the part and produces subtle textural transformations.

The black oxide process causes the surface to become slightly more porous. Popular names for this conversion coating include: “black oxide”, “black passivating”, “oxidizing”, “gun bluing” and “blackening”. Components which undergo this finishing process won’t reflect as much light.


Types of Black Oxide Treatments

Manufacturers currently utilize several different treatments to achieve black oxide coatings of ferrous metals. Two broad categories include “Hot Blackening” and “Cold Blackening”. The proprietary coatings used to complete this surface treatment often contain unique formulations.

Hot Blackening

During hot blackening, a manufacturer typically cleans a part and then submerges it in a salt bath at high temperatures before rinsing. The procedure varies widely based upon the individual proprietary formula used to achieve a black oxide coating. This finishing treatment usually occurs in an industrialized environment and often requires the use of caustic chemicals.

Cold Blackening

Some inventors have developed proprietary blackening treatments which can occur at normal room temperatures. These formulations also depend upon chemical reactions taking place on the surface of the metal. Although usually easier to implement, the cold blackening process may not generate an aesthetically pleasing coated surface.


Zinc Oxide

The inorganic compound known by chemists as “zinc oxide” has obtained widespread use in industrial processing as an additive. For instance, some manufacturers add this chemical to rubber, cement, lubricants and other products. When added to paint, zinc oxide enhances the ability of the paint to withstand corrosion.

Possibly some modern manufacturers include zinc oxide as an additive in some proprietary formulations for blackening copper surfaces. If offers a wide array of potential uses. Zinc oxide contributes to numerous commercial manufacturing processes.


Materials And Applications

Over the centuries, manufacturers have utilized a variety of materials during the course of generating black oxide conversion coatings for ferrous metal items. Numerous applications exist for parts subjected to this type of surface treatment.


Black oxide coatings protect many ferrous metal, stainless steel and steel parts. Additionally, manufacturers have developed specialized proprietary coatings to produce black oxide coatings for zinc and copper components, also. Although through trial and error, this surface treatment may occur in some low-tech environments, most manufacturers who generate high volumes of parts require blast furnaces with temperature control systems, salt baths and mechanized cleaning and rinsing facilities. Automation may help generate large quantities of black oxide coated metal components. The use of black oxide coatings often occurs in conjunction with treatments using oil, clear wax or even acrylic to further enhance a part’s corrosion resistance.


Many applications exist for metal parts coated in black oxide within firearms and munitions manufacturing plants. Additionally, components intended for use in inhospitable environments may benefit from undergoing this finishing process. Metal lawn furniture, outdoor tools and a variety of gardening and consumer goods all display greater durability following black oxide coating, for instance.

Today, some manufacturers utilize black oxide conversion coating to treat parts used in fencing materials. Both the automotive industry and recreational vehicle manufacturers sometimes seek this finishing process to better protect components exposed to heavy daily use or harsh conditions. Additionally, aerospace products and industrial machinery components display enhanced resistance to corrosion after undergoing this treatment.


Advantages of The Black Oxide Process

The use of black oxide conversion coatings on some metal products offers important advantages.

  1. This finishing treatment will improve corrosion resistance, especially when used in conjunction with some other surface treatments, such as the application of oil or waxes. If a manufacturer expects a metal component to faced rugged environmental demands, using this expensive treatment process may ultimately enhance the quality and anticipated durability of the part.
  2. By altering the surface of ferrous metal or steel products, and slightly increasing porosity, black oxide conversion coatings help prepare a part to accept a primer or paint coating more readily. For example, this type of finishing treatment permits surface changes which enable primers to cling more effectively to a metal component. Using black oxide coatings may ultimately reduce the surface preparation required before primer or paint applications.
  3. The use of black oxide changes the appearance of metal parts. This transformation offers aesthetic benefits in some circumstances. For instance, some firearms manufacturers may consider a blackened surface of a gun barrel more appealing to customers. Depending upon the purpose of the component, the change may increase the product’s marketplace competitiveness.
  4. By darkening metal components, black oxide coatings reduce light reflectivity and increase light absorption. This situation holds benefits for some products. Black oxide coatings provide a useful manufacturing finishing process!


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From a contract manufacturing firm, BuntyLLC evolved into a full service custom machined, forged and cast metal parts fabrication enterprise. We supply global solutions from our headquarters in Greenville, South Carolina.

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