Alodine 1200S at a glance
Where to buy| Item | Value | Source |
|---|---|---|
| Product | BONDERITE M-CR 1200S AERO, known as Alodine 1200S; brown powder | Henkel TDS, Nov 2019 |
| Approval | QPL-81706; makes Class 1A and Class 3 coatings under MIL-DTL-5541, bare or painted | Henkel TDS |
| Make-up | 6.3 lb per 100 gal (7.5 kg per 1000 L); 12.5 lb (15 kg) for brush application | Henkel TDS |
| pH | 1.3 to 1.8 | Henkel TDS |
| Temperature | 68 to 95 F (20 to 35 C) | Henkel TDS |
| Contact time | 15 to 180 seconds | Henkel TDS |
| Finished colour | Light iridescent golden to tan | Henkel TDS |
| Rule on repairs | Apply immediately after corrosion removal and rinse; recoat if 48 h pass before primer or paint | AC 43.13-1B par. 6-136d(2)(e), 6-136j |
These figures belong to this one Henkel sheet. Another product, or another revision, has its own. The SRM names the conversion coat for the repair.
Alodine 1200 / 1200S chromate conversion coat
What it is. A powder mixed with water to make an acid solution that converts the aluminium surface into a thin protective chromate film. It also gives paint a better bond (Henkel TDS).
What it is for. Restoring the surface film after corrosion removal, blending, drilling and cutting, which break the anodic film (AC 43.13-1B par. 6-133, 6-134).
How it is used. Process: clean, water rinse, deoxidize if heavily oxidized, rinse, treat by immersion, brush or spray, rinse, dry (Henkel). Use acid-resistant containers of wood, rubber, stainless steel or plastic; lead, glass, tin and galvanized iron are not to be used (Henkel, brush application). Keep it off magnesium and off steel over 180,000 psi (AC note to 6-136).
Life and cure. Paint-over window: if 48 hours or more pass after the coat and no primer or paint is on it, apply it again (AC 6-136j). Bath life and rinse times belong to the maker's sheet.
Safety. The AC names Alodine 1200 among the materials needing gloves, eye or face protection and clean water at hand (par. 6-90a). It also warns that conversion-coat solutions must not contact paint thinner, acetone or other combustible material. Read the SDS.
Specification. MIL-DTL-5541 (Class 1A and Class 3). AC 43.13-1B still uses the old numbers MIL-C-81706 and MIL-C-5541.
Equivalents. Henkel sells Alodine 1200S as BONDERITE M-CR 1200S AERO. A different maker's product qualified to the same specification is a candidate only if the SRM allows it.
What MIL-DTL-5541 and MIL-DTL-81706 are
MIL-DTL-5541 is the performance specification for chemical conversion coatings on aluminium and its alloys. MIL-DTL-81706 is the specification for the chemical materials (the powders and liquids) that make those coatings; Henkel lists its product on QPL-81706. Older documents, including AC 43.13-1B, carry the earlier numbers MIL-C-5541 and MIL-C-81706.
Standard summaries say Class 1A is for maximum corrosion protection and Class 3 is for low electrical resistance, as in bonding surfaces. We did not read the specification text: confirm the class in the SRM.
Chromate conversion coats are hexavalent-chromium products, and chrome-free pretreatments exist. PPG's CA7502 sheet names DesoGel EAP-9 and EAP-12 pretreatments as alternatives to a MIL-DTL-5541 coat under its chrome-free primer. Whether one may replace Alodine on a repair is the SRM's decision.
Questions people actually ask
Why the 48 hour rule?
A conversion coat that sits bare loses its value as a paint base. The AC says to recoat if 48 hours or more pass without primer or final paint (par. 6-136j).
Can I apply Alodine to magnesium?
The AC says not to let these solutions touch magnesium or high-strength steel. Magnesium has its own chromic acid pretreatment in the AC.
Is Alodine the same as anodizing?
No. Anodizing is an electrolytic process that builds an oxide film. Alodine is a chemical dip, wipe or brush. The AC prefers anodizing for doublers, with a conversion coat as the alternative (par. 6-134d).
Limits — when NOT to use this
What the sources support, and no further.
- One product sheet. Bath data are from the Henkel M-CR 1200S AERO TDS (Nov 2019). Other products differ.
- Class meanings are from standard summaries; we did not read the MIL-DTL-5541 text.
- Hazard rules are the AC's and the SDS's. We add none.
Where to buy
Distributors coming soon.
Sources
- FAA AC 43.13-1B CHG 1, Chapter 6 (corrosion control, safety precautions, finishes) — Pars. 6-90 (safety precautions), 6-134 to 6-136 (finish, conversion coat, 48 hour rule, fasteners), section 4 (corrosion preventive maintenance, MIL-C-16173 Grade 4); par. 5-63 (cleaner types).
- Henkel, Technical Data Sheet BONDERITE M-CR 1200S AERO (known as Alodine 1200S), November 2019 — QPL-81706, Class 1A and 3 under MIL-DTL-5541, bath make-up, pH, temperature, time, process steps, equipment.
- PPG Aerospace, Desoprime CA7502 Chrome-Free Epoxy Primer, Technical Data Sheet — Chrome-free primer: mix ratio, pot life, film thickness, qualifications.