AMS-M-3171
Magnesium Alloy, Processes for Pretreatment and Prevention of Corrosion on
Covers apparatus, materials, and processes for increasing corrosion resistance of magnesium alloys and preparing them for organic coating systems.
What AMS-M-3171 specifies
AMS-M-3171 is SAE's adopted replacement for the former MIL-M-3171 magnesium pretreatment document. It contains multiple legacy chemical and anodic processes rather than one interchangeable conversion coating: examples include Type I chrome pickle, Type III dichromate, Type IV galvanic anodizing, Type VI brush-on treatment, Type VII fluoride anodizing, and Type VIII chromate treatment. These treatments generally serve as temporary protection or a paint base, and several use hexavalent chromium. Buyers must name the exact type, alloy, surfaces, paint system, touch-up permission, and environmental restrictions instead of calling out only the base document.
AMS-M-3171 types and classes
Every designation the document defines, with the thickness it requires and the tests it imposes.
| Designation | Meaning | Requirement / test |
|---|---|---|
Type I | Legacy Dow 1 chemical pickle for temporary protection and paint preparation. | Appearance and process control. |
Type III | Legacy Dow 7 dichromate treatment for magnesium alloys. | Appearance and process control. |
Type IV | Legacy Dow 9 galvanic anodic process. | Appearance and process control. |
Type VI | Legacy Dow 19 treatment used for local application and touch-up. | Appearance and process control. |
Type VII | Electrolytic fluoride-based treatment followed by specified post-treatment. | Process qualification and appearance. |
Type VIII | Chromate treatment used as protective coating and paint base. | Appearance and process control. |
Tests and the drawing call-out
Tests the document imposes
- Visual appearance and coverage
- Process-solution control
- Paint-system adhesion where required
- Corrosion evaluation required by the selected type or procurement document
How to cite it
Drawing call-out
TREAT MAGNESIUM PER AMS-M-3171, TYPE <I|III|IV|VI|VII|VIII>, <PAINT BASE|TEMPORARY PROTECTION>, <MASKING>Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
Finishes specified to AMS-M-3171
AMS-M-3171 — frequently asked
Is AMS-M-3171 one conversion-coating process?
No. It collects several chemical and anodic processes with materially different chemistry and dimensional effects. Always specify the type.
Are AMS-M-3171 coatings chrome-free?
Many legacy types use hexavalent chromium and must not be assumed RoHS-compliant. A chrome-free alternative requires explicit engineering approval and processor qualification.
Is the coating enough for outdoor magnesium service?
Usually it is a pretreatment or temporary protective layer rather than the complete exterior system. Prompt priming and painting are normally needed for durable service.
AMS-M-3171 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 ↗