AMS 2404
Plating, Electroless Nickel-Phosphorous
Covers requirements for electroless nickel-phosphorus deposited on various materials.
What AMS 2404 specifies
AMS 2404 controls electroless nickel-phosphorus plating and four post-plating thermal classes. Class 1 has no post-plating thermal treatment except hydrogen-embrittlement relief. Class 2 is heated at 450 to 800 °F to harden the deposit. Class 3 is heated at 375 °F to improve adhesion on non-heat-treatable aluminum and beryllium alloys. Class 4 is heated at 250 °F to improve adhesion on heat-treatable aluminum. Unless otherwise specified, substrate-linked minimum thicknesses are 0.0015 in on ferrous alloys, 0.0010 in on aluminum, and 0.0005 in on copper, nickel, cobalt, titanium, and beryllium alloys. The drawing should state class, thickness, basis alloy, heat-treatment details, masking, and embrittlement requirements.
AMS 2404 types and classes
Every designation the document defines, with the thickness it requires and the tests it imposes.
| Designation | Meaning | Coating weight | Requirement / test |
|---|---|---|---|
Class 1 | No post-plating thermal treatment except required hydrogen-embrittlement relief. | Default substrate minimum: ferrous 38.1 µm; aluminum 25.4 µm; copper, nickel, cobalt, titanium, and beryllium 12.7 µm. | Thickness, adhesion, corrosion resistance where applicable, deposit composition when specified, and embrittlement control. |
Class 2 | Thermally treated at 450–800 °F (232–427 °C) to harden the deposit. | Same substrate-linked thickness defaults unless otherwise specified. | Deposit hardness of at least 800 HK100, thickness, adhesion, and applicable corrosion and embrittlement tests. |
Class 3 | Thermally treated at 375 ± 15 °F (191 ± 8 °C) for 1–1.5 h to improve adhesion on non-heat-treatable aluminum and beryllium alloys. | Same substrate-linked thickness defaults unless otherwise specified. | Thickness and adhesion after the specified thermal treatment. |
Class 4 | Thermally treated at 250 ± 10 °F (121 ± 6 °C) for 1–1.5 h to improve adhesion on heat-treatable aluminum. | Same substrate-linked thickness defaults unless otherwise specified. | Thickness and adhesion after the specified thermal treatment. |
Tests and the drawing call-out
Tests the document imposes
- Coating thickness
- Adhesion per ASTM B571 or the approved substrate-specific method
- Corrosion resistance on applicable steel specimens
- Class 2 hardness of at least 800 HK100
- Hydrogen-embrittlement relief per AMS 2759/9 for susceptible steel
- Hydrogen-embrittlement acceptance testing when specified
How to cite it
Drawing call-out
ELECTROLESS NICKEL PER AMS 2404 CLASS <1|2|3|4>, <THICKNESS>, [PHOSPHORUS REQUIREMENT], [HYDROGEN-RELIEF REQUIREMENT], [MASKING]Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
Finishes specified to AMS 2404
AMS 2404 — frequently asked
What is AMS 2404 Class 1 versus Class 2?
Class 1 receives no post-plate thermal treatment except embrittlement relief. Class 2 is heated at 232–427 °C to harden the electroless nickel deposit.
What thickness does AMS 2404 require?
Unless the drawing states otherwise, the default minimum depends on substrate: 38.1 µm on ferrous alloys, 25.4 µm on aluminum, and 12.7 µm on the listed nonferrous alloys.
Does AMS 2404 replace MIL-C-26074?
It is widely used as a modern successor, but the documents are not automatically interchangeable. Class, thickness, corrosion, and testing requirements must be translated by engineering.
AMS 2404 is copyrighted by SAE International. This page explains the document so a drawing can be read; it does not reproduce the standard. Purchase the current edition from the publisher. Official source ↗