Overview of Oxide Black Finishing of Precision Mechanical Parts
Knowledge

Overview of Oxide Black Finishing of Precision Mechanical Parts

Generally, the steel blackening (black oxidation) treatment can effectively improve the corrosion resistance, but the protective effect is still quite limited. Oil immersion or subsequent rust prevention treatment is still required to really improve the corrosion resistance and lubricity of the blackened layer.
Published: May 12, 2020
Overview of Oxide Black Finishing of Precision Mechanical Parts

To improve the anti-rust ability of steel parts, the surface of the steel parts is oxidized into dense and smooth iron oxide with strong oxidants. This thin layer of ferro ferric oxide can effectively protect the inside of the steel from oxidation. The ferro ferric oxide oxidized at high temperature (about 550 ℃) is sky blue, so it is called bluish treatment. The ferric oxide formed at low temperature (about 3 50 ℃) is dark black, so it is called blackening treatment. In weapons manufacturing, the bluish treatment is commonly used; in industrial production, the bluish treatment is commonly used.

Whether it is possible to oxidize the dense and smooth iron trioxide on the surface of steel depends on choosing a strong oxidant. The strong oxidant is composed of sodium hydroxide, sodium nitrite and trisodium phosphate. When they are blue, they use their molten liquid to treat steel parts; when they are black, they use their aqueous solutions to treat steel parts.

Precision-machined parts made of iron-based materials (stainless steel alloys) can specify black oxide as a surface treatment agent, thereby providing extra protection for the parts.

What is black oxide?

Oxide black is a conversion film that is produced by a chemical reaction when the part is immersed in an alkaline salt solution (usually heated). The reaction between the stainless-steel alloy and the solution will produce magnetite on the surface of the part. Magnetite acts as a protective barrier to prevent moisture from corroding the alloy surface. Magnetite is black, so the name is "black oxide".

The solution for this process varies slightly depending on the metal to be applied. It can be applied in cold, room temperature, or hot processing methods, and may require pre-treatment of components according to component requirements.

Another advantage of black oxide is that this process only produces a very thin layer of magnetite, which forms a moisture barrier. Typical thickness is 5-10 millionths of an inch (.000005 inches -.000010 inches). This means that the process will not affect the dimensional stability of the part. Another advantage is that no metal is removed or deposited from the surface of the part during processing. Unlike painted or electroplated surface treatment, black oxide will not chip or flake.

It can also be post-treated (oil, wax or varnish), depending on the application and aesthetic requirements of the final part, changing the surface treatment from satin to gloss. After trimming, it can also provide improved lubrication characteristics, which helps to make parts run more smoothly and easy to connect with the matching parts. The oil also enhances corrosion protection. If black oxide is not specified in any post-treatment, the treatment process is usually completed with oil.

The application of black oxide can be specified

  • Components that must meet MIL-DTL-13924D specifications for military applications.
  • Surgical instruments in a light-dense environment can reduce eye strain.
  • For gears, fasteners, and hardware used in components requiring corrosion resistance.
  • Black hardware used for construction and furniture assembly adds to the aesthetic appeal of the final product.
Important factors to consider when specifying black oxide.
  • The period of protection
  • Indoor or outdoor applications
  • Desired appearance (matte or gloss)
  • Environment (humidity, steam, temperature)
  • The end use of the product

Test options
There are various test options for black oxide surface treatment. If any of these tools are needed, they will be specified on the part drawing, and this test usually adds time and cost to the test.

Stain Test
This process will determine if there are black powdery residues on the parts when rubbed by hand. The test is carried out after completion. Relative Humidity - This procedure will use the ASTMD 2247 standard specification (for testing the water-resistance of coatings at 100% relative humidity) to test corrosion resistance.

Published by May 12, 2020 Source :pioneerserviceinc, Source :itsfun

Further reading

You might also be interested in ...

Headline
Knowledge
Redefining Makeup Removal: Evolving from Traditional Nonwovens to Medical-Grade Standards
As skincare routines become increasingly refined, makeup removal products are no longer secondary tools used solely for eliminating cosmetics. Instead, they have become the first line of defense for skin health, anti-irritation performance, and the sensory experience of daily rituals. The material composition and structural engineering of removal substrates—such as cotton pads, cleansing cloths, and wipes—are undergoing continuous optimization. The industry is shifting from simple absorbent functions toward advanced development that combines low friction, minimal residue, enhanced skin compatibility, and environmental sustainability.
Headline
Knowledge
The Superpower of PCBs: Unveiling the Magic of Heat Dissipation
Every PCB is like a bustling miniature city: the electric current flows like nonstop traffic, and the electronic components are the lively citizens. When “traffic jams” occur, heat builds up quickly. Without proper thermal design, LEDs, CPUs, and power transistors can “overheat” and fail. A PCB isn’t just a circuit-connecting board—it also acts as the city’s “air-conditioning engineer.” Copper traces serve as high-speed distribution lanes, thermal vias function like air ducts, and the board material and metal backing work as invisible heat-dispelling magic. Combined with airflow management inside the enclosure, the PCB efficiently channels heat away, ensuring components perform reliably and quietly safeguarding the entire electronic system.
Headline
Knowledge
From Marine Polysaccharides to Pet Wellness: A New Milestone in Fucoidan Applications
In recent years, companion animals have come to occupy an increasingly significant role in human life—not merely as pets, but as integral members of the family. As pet owners place growing emphasis on animal health and longevity, the demand for functional health ingredients has surged. Among these, fucoidan, a marine-derived polysaccharide extracted from brown seaweed, has emerged as a key player in the field of pet nutritional science. Recognized for its immunomodulatory, antioxidant, and cellular repair properties, fucoidan is redefining the standards for preventive care and holistic wellness in companion animals.
Headline
Knowledge
Eco-Friendly Tableware and Food Safety: A Choice for Both the Environment and Health
With a global increase in plastic reduction and environmental awareness, a growing number of businesses and consumers are opting for eco-friendly tableware made from natural or biodegradable materials to replace traditional plastic items. Eco-friendly tableware—such as that made from bamboo fiber, sugarcane bagasse, leaf fiber, or PLA—typically does not contain harmful substances like plasticizers or BPA, thus reducing potential health risks. According to the European Union's Food Contact Materials Regulation (EC No. 1935/2004), "food contact articles shall not transfer their constituents to food in quantities that could endanger human health." However, when production processes or manufacturing technologies are inadequate, eco-friendly tableware can still pose food safety risks.
Headline
Knowledge
Food Cleanliness and Its Impact on the Human Body: A Farm-to-Table Guarantee
The cleanliness of food, defined as the hygienic state of food surfaces and production environments, is crucial for consumer health. The World Health Organization (WHO) reports that globally, approximately 600 million people fall ill each year from consuming contaminated food, leading to about 420,000 deaths.
Headline
Knowledge
Green Printing Transformation Becomes the Core Competitiveness of a Sunset Industry
As global concerns over climate change, plastic pollution, and carbon emissions intensify, the printing industry is undergoing a profound green transformation. From packaging and commercial publishing to labels and promotional materials, green printing is no longer just an added value—it's becoming a fundamental requirement for brand compliance and supply chain standards.
Headline
Knowledge
From Equipment to System: Building a Highly Consistent and Maintainable Smart Coffee Platform
In today’s retail and service environments, smart coffee solutions that offer high consistency, scalability, and ease of maintenance have become key criteria for commercial adoption. Based on advanced automation control technologies and incorporating Specialty Coffee Association (SCA) brewing standards, this platform integrates modular hardware architecture, data-driven algorithms, and cloud-based remote management. It enables comprehensive deployment—from standalone machines to full-site integration. This system-oriented design not only enhances product stability and flavor reproducibility, but also significantly reduces maintenance costs, making it an ideal solution for chain retailers, branded venues, and smart vending scenarios.
Headline
Knowledge
Development Trends of Intelligent Industrial Lifting Equipment
As global manufacturing accelerates its transition toward smart transformation, the demand for industrial lifting equipment and lubrication systems continues to rise. The Taiwan and Asia-Pacific markets are steadily expanding, with increasing demand for high-safety and precision-controlled lifting and lubrication equipment in the automotive repair and industrial manufacturing sectors. The advancement of smart manufacturing has promoted the integration of intelligent sensing and remote monitoring technologies, making these devices the core driving force of smart factories, fueling rapid market growth and serving as a key driver for Fugimaku’s continuous innovation and development.
Headline
Knowledge
The Tough Hero of the Tool World: The Secrets of Tungsten Carbide
In the world of industrial cutting tools, tungsten carbide is like a superhero: extremely hard, wear-resistant, heat-tolerant, and remarkably tough, able to stay sharp without chipping during high-speed cutting and prolonged machining. From rough milling to precision engraving, its variety of tool shapes and coating technologies allow it to tackle diverse challenges. Its applications even extend beyond cutting tools to wear-resistant parts, mining bits, and even fashion accessories. Whether in automotive components, aerospace molds, or everyday aesthetics, tungsten carbide stands as a reliable powerhouse in modern manufacturing. This article will take you deep into the material’s properties, machining principles, and real-world applications.
Headline
Knowledge
Professional Analysis and Application Value of Pneumatic Tools
Pneumatic tools are a category of industrial equipment powered by compressed air, widely used across manufacturing, assembly, maintenance, and construction sectors. Compared with electric tools, pneumatic tools are lighter in weight, deliver consistent output, offer high durability, and provide superior safety. These advantages make them the preferred choice for professionals in scenarios that require prolonged, high-frequency, and high-precision operations.
Headline
Knowledge
Common Chronic Diseases and Their Characteristics: A Personalized Health Management Guide
In pursuit of a fast-paced life, we often overlook our body's warning signs. According to the Health Promotion Administration, Ministry of Health and Welfare, chronic diseases like hypertension and diabetes have become a hidden threat to public health. Though these conditions progress slowly, long-term neglect can lead to serious consequences such as heart disease or stroke. This article will help you understand their causes and provide a simple “self-health management process” to proactively take control of your health.
Headline
Knowledge
Professional Analysis of Freight Logistics: From Transportation Management to Smart Supply Chains
Freight logistics is a critical component of modern supply chains. It encompasses not only the transportation of goods from origin to destination but also transportation planning, risk management, warehousing, and the integration of information technology. Professional freight operations can significantly enhance transportation efficiency, reduce costs, and ensure the safety of goods.
Agree