The stakes couldn’t be higher when aerospace and defense components fail. That’s why the specifications governing protective coatings matter so much. Among the most critical is AMS 2404. It is the standard for electroless nickel plating that has become essential for mission-critical applications.

At The Lindgren Group, we’ve seen firsthand how parts treated to AMS 2404 standards significantly outperform untreated components in harsh environments. Here’s what you need to know about this important specification and how it protects your most important assets.

What Is AMS 2404?

AMS 2404 is a Society of Automotive Engineers (SAE) Aerospace Material Specification that covers the engineering requirements for electroless nickel-phosphorus plating on various materials. The current version is AMS 2404K, reaffirmed as recently as 2024 and active through at least 2027.

Electroless nickel (EN), unlike traditional electroplating, uses an auto-catalytic chemical reaction rather than an electrical current to deposit a uniform nickel-phosphorus alloy. This fundamental difference delivers significant performance advantages.

The key distinction is that the military specification MIL-C-26074 has been superseded by AMS 2404. While you may still see references to the old Mil-Spec in legacy documentation, AMS 2404 is now the governing standard for new designs and current production.

Why Electroless Nickel?

Electroless nickel plating offers a combination of protective properties that make it invaluable for aerospace and defense applications:

  • Uniform coating distribution:  EN deposits evenly on complex geometries, including recesses, blind holes and internal threads. This is one of its most significant advantages over electroplating, which tends to build up on edges and corners while leaving recesses under-protected.
  • Superior corrosion resistance: High-phosphorus EN (10.5-12% phosphorus) provides exceptional barrier protection against harsh environments, including salt spray, humidity and de-icing chemicals.
  • Wear resistance:  The deposit hardness enhances substrate surfaces, protecting components exposed to high-friction environments like landing gear and engine parts.
  • EMI shielding: As aircraft rely more heavily on electronic systems, EN provides effective electromagnetic interference protection for sensitive electronics.

Understanding AMS 2404

AMS 2404 specifies four distinct classes of electroless nickel plating, determined by post-treatment requirements.

Class 1 – As Coated (No Post-Plate Thermal Treatment)

Parts receive no heat treatment after plating – except for hydrogen embrittlement relief when required. Suitable for applications where as-deposited properties meet requirements.

Class 2 – Hardened Deposit (Thermal Treatment at 450°F/232°C or Above)

Heat treatment increases deposit hardness for enhanced wear resistance. Ideal for components experiencing friction or abrasion.

Class 3 – Adhesion Treatment for Non-Heat Treatable Aluminum and Beryllium Alloys (375°F/191°C)

Designed for substrates that cannot be heat treated for strength but require improved adhesion between the EN deposit and the base material.

Class 4 – Adhesion Treatment for Heat Treatable Aluminum Alloys (250°F/121°C)

Specifically for aluminum alloys that undergo separate heat treatment processes. The lower temperature preserves the alloy’s heat-treated properties while ensuring coating adhesion.

Unless a specific class is specified on the drawing, Class 1 shall be supplied.

The Three Grade: Thickness Requirements

AMS 2404 (and its predecessor MIL-C-26074) defines three grades based on minimum thickness requirements beyond class selection:

  • Grade A: 0.0010 inch minimum – Required for aluminum alloys.
  • Grade B: 0.0005 inch minimum – Specified for copper, nickel and cobalt alloys.
  • Grade C: 0.0015 inch minimum – Required for ferrous alloys (steel and iron-based materials).

The appropriate grade depends on the substrate material and the service environment the component will face.

Performance Benefits in Harsh Environments

So why does AMS 2404 matter for component life? The data speaks for itself.

  • Corrosion Protection: High-phosphorus EN deposits create an amorphous structure. Meaning no grain boundaries where corrosion can initiate. This provides a true barrier layer that protects the substrate even in marine atmospheres and chemical exposure.
  • Wear Resistance That Lasts: The hardness of electroless nickel can be further enhanced through heat treatment (Class 2). For extreme applications, EN also allows co-deposition of particles like silicon carbide, PTFE or even diamonds to achieve specific wear or lubricity properties.
  • Salvage of Mismachined Parts: It’s extensively used to salvage mismachined components because EN plates uniformly rather than building on edges. The uniform deposit maintains tolerances while restoring dimensions.
  • High-Temperature Performance: Electroless nickel coatings perform reliably in service temperatures up to 1000°F (538°C).

Why Choose The Lindgren Group for AMS 2404 Plating?

Meeting AMS 2404 requires process control, testing rigor and deep expertise. The Lindgren Group delivers:

    • Nadcap Accreditation: Our aerospace and defense work meets the National Aerospace Defense Contractors Accreditation Program’s stringent process control requirements.
  • CMMC Level 2 Certified: The Lindgren Group successfully passed its CMMC 2.0 audit and is now certified. We successfully engaged with an authorized C3PAO or Certified Third-Party Assessment Organization.This certification is now a common prerequisite for new Department of War contracts.
  • ISO Certification: We maintain rigorous quality management systems across all operations.
  • ITAR Compliance: We’re certified for International Traffic in Arms Regulations, essential for defense work.
  • Comprehensive Testing: AMS 2404 requires acceptance testing (visual inspection and thickness validation), periodic testing (adhesion and corrosion) and pre-production testing for new applications.
  • Years of Experience: Our team at Nico Products and Avtec Finishing Systems brings deep expertise in electroless nickel plating for the most demanding applications.

Making the Right Choice for Your Components

When your parts need to survive harsh environments – whether that’s high altitude, salt spray, chemical exposure or mechanical wear – AMS 2404 electroless nickel plating provides proven protection.

The specification’s class and grade system allows you to match the coating precisely to your application requirements. And when you partner with The Lindgren Group, you get the expertise and quality systems needed to ensure compliance and performance.

Ready to enhance your component reliability? Contact The Lindgren Group today to discuss your AMS 2404 electroless nickel plating requirements.