AnoSpecification
MIL-DTL-5541 chem film, decoded and run.
The specification for chemical conversion coatings on aluminum. Corrosion protection that keeps the surface conductive, in clear and gold, Class 1A and Class 3.
What the spec covers
Protection without insulation.
MIL-DTL-5541 governs chemical conversion coatings, the thin films that protect aluminum from corrosion while leaving it electrically conductive. That combination is why avionics housings, ground planes, and painted assemblies carry a 5541 callout. The spec's two types describe the chemistry (Type I traditional hexavalent, Type II trivalent), and its two classes describe the job: Class 1A for maximum protection, Class 3 for low contact resistance.
Choosing the class
1A or 3, decided by the part's job.
| THE PART NEEDS | CALL OUT | WHY |
|---|---|---|
| Weather and salt exposure | Class 1A | Thickest film, maximum corrosion protection |
| Grounding or bonding path | Class 3 | Thinner film, lowest contact resistance |
| Base under a paint system | Class 1A typical | Paint spec may direct otherwise |
| EMI shielding surfaces | Class 3 | Conductivity is the point |
The specification text lives on the government's ASSIST library at quicksearch.dla.mil. We also support the NASA/JSC PRC-5005 process specification for conversion coating work.
Where it runs
Run alongside the anodize line.
Chem film runs in the same shop, on the same 3 to 4 day clock, with the same batch QC. Parts that need both finishes on different surfaces get masked to the print.
GOLD FINISH WORK · THE BENCHQuestions
MIL-DTL-5541, asked and answered
What does a MIL-DTL-5541 callout mean?
Chemical conversion coating on aluminum: Type I or II chemistry, Class 1A for maximum corrosion protection or Class 3 for low electrical resistance, in clear or gold.
Is 5541 the same as Alodine or chromate?
Alodine is a trade name and chromate is the chemistry family; MIL-DTL-5541 is the specification that governs them. A drawing calling out any of the three lands in the same tank.
Why choose 5541 over anodize?
When the part needs to stay electrically conductive: grounding, bonding, EMI shielding, or a base under paint. Anodize insulates; chem film does not.
Do you run both classes?
Yes, Class 1A and Class 3, clear and gold, to the callout on the print.
Ready when you are
5541 to the letter, on the date.
Send the callout and the count. Quotes by email, expedites by text.