FC-9.5-M
Light rust remover
Ingredients
| Ingredient | % w/w | Function |
|---|---|---|
| Phosphoric acid (85%) | 15.0–25.0 | Primary acid, rust converter |
| 2-Butoxyethanol | 2.0–4.0 | Penetrant, co-solvent |
| SLES (28%) | 1.0–2.0 | Wetting agent |
| Benzotriazole (BTA) | 0.1 | Corrosion inhibitor |
| Deionized water | to 100 | Carrier |
| Colorant | 0.002 | Safety |
Formulation Notes
Iron oxide rust stains are addressed through a conversion reaction unique to phosphoric acid:
Rather than dissolving rust, phosphoric acid converts it to ferric phosphate (), an inert, adherent layer that inhibits further oxidation and provides a suitable substrate for paint adhesion .
Target parameters: pH 2.0–3.0; viscosity 3–8 cP (thin liquid for penetration); phosphoric acid content 13–21% active.
At 20% phosphoric acid (85% solution, ~17% active), surface rust converts to within 10–20 minutes at room temperature; reaction kinetics increase with temperature . 2-Butoxyethanol improves acid ingress into porous rust layers. After treatment, the darkened phosphate layer should be rinsed; for aesthetic restoration, light abrasion removes the gray film. Not for use on aluminum, zinc, or galvanized surfaces.