MIL-C-26074
Coatings, Electroless Nickel, Requirements for
Legacy specification for electroless nickel-phosphorus coatings on metal and composite surfaces.
Superseded: MIL-DTL-32119 and SAE AMS-C-26074; AMS 2404 is a commonly specified successor. New drawings should cite the successor; existing call-outs to MIL-C-26074 remain understood.
What MIL-C-26074 specifies
MIL-C-26074E is a cancelled legacy electroless-nickel specification that remains common on older drawings. Classes 1 through 4 define post-plating heat treatment: as plated, hardened, adhesion-treated non-heat-treatable aluminum or beryllium, and adhesion-treated heat-treatable aluminum. Grades A, B, and C define minimum thickness by substrate group rather than increasing severity: 0.0010 in on aluminum, 0.0005 in on copper, nickel, cobalt, titanium, and beryllium, and 0.0015 in on ferrous alloys. Cancellation and replacement history is complex; MIL-DTL-32119 and SAE AMS-C-26074 are named replacements, while AMS 2404 is widely used for modern aerospace electroless nickel. A legacy note should not be converted without an engineering equivalence review.
MIL-C-26074 types and classes
Every designation the document defines, with the thickness it requires and the tests it imposes.
| Designation | Meaning | Thickness | Coating weight | Requirement / test |
|---|---|---|---|---|
Class 1 Grade A | As-plated electroless nickel on aluminum-base alloys; hydrogen-relief bake is not treated as a Class 2 hardening treatment. | ≥ 25 µm ≥ 1 mil | — | Thickness, adhesion, corrosion resistance when applicable, and hydrogen-embrittlement control for susceptible steel. |
Class 1 Grade B | As-plated electroless nickel on copper, nickel, cobalt, titanium, or beryllium alloys. | ≥ 13 µm ≥ 0.5 mil | — | Thickness and adhesion; corrosion test applicability depends on substrate and order. |
Class 1 Grade C | As-plated electroless nickel on iron-base alloys. | ≥ 38 µm ≥ 1.5 mil | — | Thickness, adhesion, corrosion resistance, and hydrogen-embrittlement control. |
Class 2 | Post-plating heat treatment to obtain required hardness; used on substrates that tolerate 500 °F (260 °C) or above. | — | Grade A, B, or C minimum also applies. | Thickness, adhesion, required hardness, and applicable corrosion and embrittlement tests. |
Class 3 | Post-treatment of non-heat-treatable aluminum alloys and beryllium alloys to improve deposit adhesion. | — | Applicable grade minimum also applies. | Thickness and adhesion after the specified thermal treatment. |
Class 4 | Post-treatment of heat-treatable aluminum alloys to improve deposit adhesion. | — | Applicable grade minimum also applies. | Thickness and adhesion after the specified thermal treatment. |
Tests and the drawing call-out
Tests the document imposes
- Coating thickness
- Adhesion after applicable heat treatment
- Corrosion resistance where applicable
- Deposit hardness for Class 2
- Hydrogen-embrittlement relief and testing for susceptible high-strength steel
- Shot peening before coating for specified fatigue-critical steel at 40 HRC or above
How to cite it
Drawing call-out
ELECTROLESS NICKEL PER MIL-C-26074 CLASS <1|2|3|4>, GRADE <A|B|C>, [THICKNESS], [MASKING]Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
MIL-C-26074 — frequently asked
Is MIL-C-26074 still active?
No. It is a cancelled legacy specification. Existing drawings need contract-specific disposition rather than silently treating an ASTM or AMS document as identical.
What replaced MIL-C-26074?
The cancellation history names MIL-DTL-32119 and SAE AMS-C-26074. AMS 2404 is also a commonly specified modern aerospace successor, while ASTM B733 uses a different classification system.
What are Grades A, B, and C?
They are substrate-linked minimum thicknesses: A is 25.4 µm, B is 12.7 µm, and C is 38.1 µm. They are not a low-to-high quality sequence.
MIL-C-26074 is a work of the US Government and not subject to copyright. The authoritative copy is the DLA ASSIST database; check it for amendments issued after this page was updated. Official source ↗