AMS 2474
Chemical Treatment for Aluminum Alloys, Low Electrical Resistance Coating
Establishes requirements for low-electrical-resistance chemical-film coatings on aluminum and aluminum alloys.
What AMS 2474 specifies
AMS 2474 is the stabilized SAE chemical-film specification for aluminum surfaces requiring low electrical contact resistance. It is functionally similar to MIL-DTL-5541 Class 3, but direct equivalence should not be assumed. The coating must provide corrosion protection while meeting contact resistance limits measured under 200 psi electrode pressure: not over 5000 µΩ/in² initially and 10000 µΩ/in² after the specified exposure. Process-control panels also receive 168-hour ASTM B117 salt spray and applicable adhesion testing. SAE points future procurement toward AMS 2477. A legacy drawing should state AMS 2474, contact areas, masking, finish system, and whether conversion to AMS 2477 is authorized.
AMS 2474 types and classes
Every designation the document defines, with the thickness it requires and the tests it imposes.
| Designation | Meaning | Requirement / test |
|---|---|---|
Low-electrical-resistance coating | Thin chemical conversion film for corrosion protection with controlled electrical contact resistance. | Initial contact resistance not over 5000 µΩ/in² and post-exposure resistance not over 10000 µΩ/in² at 200 psi; 168 h salt spray. |
Tests and the drawing call-out
Tests the document imposes
- Electrical contact resistance at 200 psi
- ASTM B117 salt spray for 168 h
- No more than 5 isolated corrosion spots per 30 in² panel and 15 per 150 in² total
- Paint adhesion when applicable
- Visual quality
How to cite it
Drawing call-out
CHEMICAL TREAT PER AMS 2474, LOW ELECTRICAL RESISTANCE, [CONTACT AREAS], [MASKING], [PAINT SYSTEM]Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
AMS 2474 — frequently asked
Is AMS 2474 the same as MIL-DTL-5541 Class 3?
They address the same functional need but are separate controlled documents. Do not substitute one for the other without customer approval.
What electrical resistance does AMS 2474 permit?
The limits are 5000 µΩ/in² as applied and 10000 µΩ/in² after exposure, measured at 200 psi electrode pressure.
Is AMS 2474 current for new designs?
AMS 2474E is stabilized, and SAE recommends AMS 2477 for future procurement. Existing drawings may continue to require AMS 2474.
AMS 2474 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 ↗