Parkerization

Parkerizing Explained: A Complete Guide to Black Manganese Phosphate Finishes

When it comes to protecting metal components from wear and corrosion, the choice of surface finish is critical. One of the most durable and trusted methods is Parkerizing. But what exactly is it, and what technical standards define it?

At Trojan Special Fasteners Ltd, we specialise in providing high-performance fasteners for demanding applications. We often supply parts that must conform to precise engineering specifications, and Parkerizing is a finish that can be supplied to meet some of the most stringent standards.

This guide answers the most common questions about this exceptional surface treatment.

What is Parkerizing?

Parkerizing is the trade name for a specific type of manganese phosphate coating. Think of it like "Hoover" for vacuum cleaners—"Parkerizing" is a brand name that has become synonymous with the process itself.

In technical terms, it is a chemical conversion coating applied to steel and iron components. The process converts the surface of the metal into a non-metallic, crystalline layer of manganese phosphate. This layer provides a rugged, dark grey to black matte finish that is highly resistant to corrosion and wear.

At Trojan Special Fasteners Ltd, when we refer to Parkerizing, we are specifically talking about Black Manganese Phosphating, which is renowned for its superior performance properties.

How does the Parkerizing (Manganese Phosphating) process work?

The process is a multi-stage chemical treatment which generally involves these key steps:

  • Thorough Cleaning: The part is completely cleaned of all contaminants like oil, grease, and rust.
  • Immersion Bath: The clean metal part is then fully submerged in a hot, acidic solution of phosphoric acid and manganese salts.
  • Chemical Reaction: The solution reacts with the steel, etching the surface and depositing a uniform, crystalline layer of manganese phosphate.
  • Rinsing: The component is removed and thoroughly rinsed to neutralise any remaining acid.
  • Sealing: Finally, the Parkerized surface is sealed, typically by immersing it in a special oil. The microporous structure of the coating is excellent at absorbing this sealant, which significantly enhances its protective properties.

What are the main benefits of a Parkerized finish?

Black Manganese Phosphating is chosen for its unique combination of protective qualities.

1. Excellent Corrosion Resistance: The non-metallic phosphate layer, combined with the sealing oil, creates a formidable barrier against moisture and oxidation.
2. Superior Wear Resistance: The hard, crystalline structure is highly resistant to scratching and scuffing, extending the service life of components.
3. Improved Lubricity & Anti-Galling: The coating's ability to hold oil provides constant self-lubrication, which is essential for threaded fasteners to prevent galling under pressure.
4. Reduces Light Glare: The dark, matte finish is non-reflective, a key reason for its widespread use in military applications.

Where are Parkerized components typically used?
Due to its rugged and durable nature, Parkerizing is specified across many demanding industries, including fasteners, military & defence, automotive, aerospace, and oil & gas.

Are there official standards for Parkerizing?
Yes. While you won't find a standard with the "Parkerizing" name, there are official British, International, and Military specifications that define the technical requirements for the manganese phosphate process. When specifying this finish on a drawing, you should refer to these standards.

International & British Standards
The primary commercial standard used in the UK and globally is BS EN ISO 9717:2017. This specification covers phosphate conversion coatings on metals and defines the requirements for achieving a consistent, high-quality finish for corrosion protection and lubricity.

Defence & Military Standards
Historically, Parkerizing’s reputation was built on its military use. For this reason, defence standards are often the most referenced specifications.

  • MIL-DTL-16232G: This is the key US military specification and is recognised worldwide. It defines Type M for Manganese Phosphate (the classic Parkerized finish) and Type Z for Zinc Phosphate.
  • DEF STAN 03-11: This is the equivalent UK Ministry of Defence standard, specifying the requirements for the phosphate treatment of iron and steel for military hardware.

For the classic, wear-resistant black finish, an engineer would typically specify "Phosphate to MIL-DTL-16232G, Type M" on a technical drawing.

Can Trojan Special Fasteners Ltd supply parts with a Parkerized finish?
Yes, absolutely. Trojan Special Fasteners Ltd can supply a vast range of standard and custom-manufactured fasteners finished with a high-quality Black Manganese Phosphate (Parkerized) coating.

We work with our specialist finishing partners to ensure that your components receive a consistent coating that meets demanding specifications such as MIL-DTL-16232G Type M and BS EN ISO 9717. Whether you need custom bolts, nuts, or other special fasteners for a demanding application, we can provide a complete solution, from manufacturing to final coating.

Get the Best Protection for Your Components with Trojan Special Fasteners Ltd
Parkerizing offers a proven, reliable, and highly effective solution for protecting critical steel components. Its unique combination of corrosion resistance, wear protection, and lubricity makes it an ideal choice for the toughest jobs.

If you require fasteners finished to a specific technical standard, contact Trojan Special Fasteners Ltd today. Our expert team is ready to discuss your project requirements and provide a competitive quote for your custom fastener needs.