Black Oxide Coating Guide: Processes and Applications

Black oxide coatings are one of the most common surface treatments used on a wide range of materials, especially metals. Therefore, in this article, we will fully explain how black oxide coatings work, their advantages and disadvantages, different types and specific applications. In addition, we will explore the various materials that are suitable for black oxide coating as well as best practices.

Table of Contents

What is Black Oxide Coating?How does black oxide work?

Pros and Cons of Black Oxide Coatings

Types of Black Oxide Coatings

Applications of Black Oxide

Materials that can be used for black oxide coatings

Differences Between Black Oxide and Other Surface Treatments

Best Practices for Black Oxide Coating

Black Oxide on Runsom's Metal Parts

Frequently Asked Questions

What is a black oxide coating?

A black oxide coating is a thin black protective layer formed on the surface of a workpiece by a chemical reaction. Typically, this coating consists of a specially treated oxide layer and is mainly used on iron and its alloys, copper or brass. In addition to enhancing the corrosion and wear resistance of metals, this coating provides good lubricity and reduces light reflection. As a result, it significantly improves the overall performance and appearance of metal parts. In addition, this treatment has a wide range of applications, from the automotive industry to the medical industry.

Now we know the definition of Black Oxide Coating. So, how does it work? The specific steps are as follows:

Pretreatment: first, the manufacturer cleans and acid-washes the metal surface to remove any dirt, grease or oxides. This step ensures that the subsequent chemical reaction goes smoothly.

Chemical Immersion: Next, the cleaned metal is immersed in a special reaction tank containing an alkaline solution. Under controlled temperature and time conditions, the metal surface undergoes an oxidizing reaction to form a dense black oxide film.

Post-treatment: After immersion, workers will wash and dry the metal. Sometimes further oil dipping or sealing treatment is required to enhance the corrosion and wear resistance of the coating.

A series of complex chemical reactions will act on the surface of the metal and eventually form a strong black oxide film, which is not only aesthetically pleasing, but also effectively protects the metal from corrosion and wear.

Advantages and disadvantages of black oxide coatings

Black oxide coating has many advantages in practical applications. However, it also has some limitations and the following are its advantages and disadvantages.

Advantages:

Good corrosion resistance: it can effectively prevent oxidation and corrosion of metal surfaces and greatly extend the service life of metal parts.

Good W ear R resistance: the coating surface is hard and dense, which improves abrasion and scuff resistance.

Good lubricating properties: It also has good self-lubricating properties, which can reduce the friction and wear of metal surfaces.

An Appearance: The coating gives metal parts an elegant black appearance, enhancing the aesthetics of the product.

COST FRIENDLY: Black oxide treatment is simpler, faster and more economical than other surface treatment processes.

LIMITATIONS.

Limited coating thickness: Black oxide coatings are typically only a few microns thick and do not provide too thick a protective layer.

Poor heat resistance: it tends to peel off or oxidize in high temperature environments.

Susceptible to damage: The coating is susceptible to mechanical damage and abrasion during assembly or installation.

Types of black oxide coatings

There are mainly the following types of black oxide coatings

1. Conventional black oxide

This is the most basic and common type of black oxide coating. It is a black oxide film obtained by immersing the metal in a solution containing sodium hydroxide and sodium nitrite. This coating has good corrosion and wear resistance, but poor heat resistance.

2. Thermal black oxide

Thermal black oxide coating, as the name suggests, is formed by chemical reaction at high temperature. Compared with the traditional method, this coating is denser and has better heat resistance, but it is also more costly.

3. Cold Black Oxide

This coating is formed by a chemical reaction at room temperature. The coating is relatively thin, but the process is simpler, faster and cheaper.

4. Composite Black Oxide

This coating is based on a basic black oxide treatment with the addition of other chemical components such as polymers or metal particles, which can further improve the corrosion, abrasion and heat resistance of the coating.

5. Electrochemical black oxide

Its use of electrochemical principles in the formation of a black oxide film on the metal surface, this method can better control the thickness and uniformity of the coating.

Application of Black Oxide

Black oxide treatment is widely used in various industries, mainly including the following fields:

Machinery manufacturing industry: such as gears, bearings, screws, springs

Electrical and electronic industry: including switches, connectors, battery boxes, etc.

Automotive and aerospace industries: engines, braking systems and landing gears

Military equipment sector: firearms and missile launchers

Medical device industry: involving surgical knives, orthopedic implants, etc.

It is an economical and practical surface treatment that plays an important role in industrial production. The following are some common materials:

Aluminum and its alloys

Stainless steel

Copper and its alloys: such as copper, brass

Carbon steel: including ordinary carbon steel, alloy steel

To ensure the quality and performance of the black oxide coating, the following best practices need to be observed:

Surface pre-treatment: thorough cleaning and pickling of metal parts

Process parameters C control: e.g. temperature, pH, concentration,

Post-treatment: washing and drying

Inspection and quality control: checking appearance, thickness, adhesion

Phosphorus protection of the environment: proper disposal of waste liquids

Process optimization: use of heat treatment or composite coatings to further improve coating properties

BOMIS is a company specializing in metal surface treatment, mainly providing various surface treatment services such as black oxidation, electroplating and spraying. In addition, the company has advanced production equipment and strict quality management system. We customize various types of black oxide coatings to meet the needs of different industries and application scenarios. If you need customized metal parts or Request an instant quote.