by Dr E. Ramanathan
Degreasing Formulations for Metal Cleaning
Degreasing is a critical step in metal cleaning to remove oils, greases, and contaminants before surface treatments like phosphating, painting, or plating. Below are different degreasing formulations based on application needs.
1. Alkaline Degreasing Formulations
Alkaline degreasers are widely used for ferrous and non-ferrous metals, offering effective cleaning without aggressive etching.
A. General-Purpose Alkaline Degreaser
Suitable for mild steel, cast iron, and general metal cleaning.
Formulation:
- Sodium hydroxide (NaOH) – 5-10% (removes heavy grease and oils)
- Sodium carbonate (Na₂CO₃) – 5-10% (softens water, mild cleaning)
- Sodium metasilicate – 2-5% (prevents redeposition, corrosion inhibition)
- Trisodium phosphate (TSP) – 3-6% (detergent action, emulsification)
- Surfactant (Non-ionic like NP-9 or NP-10) – 0.5-2% (enhances emulsification)
- Water – Balance
Operating Conditions:
- Temperature: 50-80°C
- Time: 5-15 minutes
- Agitation: Air bubbling or ultrasonic
Sodium hydroxide flakes
Sodium hydroxide Pellets
Sodium carbonate
B. Heavy-Duty Alkaline Degreaser (For Tough Grease & Carbon Deposits)
For automotive, machinery parts, and heavy industrial applications.
Formulation:
- Sodium hydroxide (NaOH) – 8-15%
- Sodium silicate – 5-8% (inhibits corrosion)
- Sodium carbonate (Na₂CO₃) – 5-10%
- EDTA (Chelating agent) – 0.5-2% (binds metal ions)
- Surfactant (Anionic like Sodium Lauryl Sulfate) – 1-2%
- Water – Balance
Operating Conditions:
- Temperature: 60-90°C
- Time: 10-20 minutes
2. Solvent-Based Degreasing Formulations
Solvent degreasers are used for removing oils and greases without water-based immersion.
A. Petroleum Solvent Degreaser
Suitable for delicate metals, precision cleaning, and non-water-sensitive applications.
Formulation:
- Kerosene or Mineral Spirits – 80-90%
- Isopropyl Alcohol – 5-10%
- Emulsifier (Polyoxyethylene nonylphenol) – 2-5%
- Corrosion Inhibitor – 0.5-1%
Application:
- Wiping or spraying at room temperature.
- No water rinsing required.
B. Chlorinated Solvent Degreaser (Non-Flammable, High-Efficiency)
For aerospace, automotive, and industrial degreasing.
Formulation:
- Trichloroethylene (TCE) or Perchloroethylene (PCE) – 85-95%
- Surfactant (Non-ionic like Triton X-100) – 2-5%
- Corrosion inhibitor – 0.5-1%
Application:
- Vapor degreasing or immersion.
- Requires proper ventilation due to solvent fumes.
3. pH-Neutral Degreasing Formulations
Safe for aluminum, brass, copper, and sensitive metals.
A. Mild Neutral Degreaser (For Soft Metals & Electronics Cleaning)
Formulation:
- Sodium bicarbonate – 2-4%
- Sodium citrate (Chelating agent) – 1-3%
- Non-ionic surfactant (e.g., Tween 80) – 1-2%
- Water – Balance
Operating Conditions:
- Temperature: 40-60°C
- Time: 5-10 minutes
4. Acid-Based Degreasing Formulations
Used before phosphating or pickling to remove oxides along with grease.
A. Phosphoric Acid Degreaser (For Pre-Treatment Cleaning)
Formulation:
- Phosphoric acid (H₃PO₄) – 5-10%
- Non-ionic surfactant – 1-3%
- Wetting agent (e.g., Sodium dodecyl sulfate) – 0.5-2%
- Water – Balance
Operating Conditions:
- Temperature: 40-70°C
- Time: 5-15 minutes
Selection Guide Based on Application:
| Application | Recommended Degreaser |
|---|---|
| Light grease & oil removal | Alkaline (General-Purpose) |
| Heavy grease, carbon, burnt oil | Heavy-Duty Alkaline |
| Non-water-sensitive metals | Solvent-Based |
| Soft metals (Aluminum, Brass) | Neutral Degreaser |
| Rust & grease removal before phosphating | Acid-Based (Phosphoric) |
Each formulation must be optimized based on metal type, contamination level, and cleaning method.
Alkaline Degreasing Powder Formulations
Powder Formulations for Alkaline Degreasing Chemicals
Powder-based degreasing formulations offer ease of handling, longer shelf life, and effective removal of oils, greases, and contaminants from metal surfaces. Below are powder formulations for both mild degreasing (general-purpose cleaning) and strong degreasing (heavy-duty cleaning).
1. Mild Alkaline Degreasing Powder (For General Cleaning)
Application:
- Used for cleaning mild steel, aluminum, and non-ferrous metals.
- Removes light grease, oil, and dirt before phosphating or painting.
Formulation:
| Ingredient | % by Weight | Function |
|---|---|---|
| Sodium carbonate (Na₂CO₃) | 40-50% | Alkaline builder, softens water |
| Sodium metasilicate (Na₂SiO₃) | 15-20% | Corrosion inhibitor, detergent booster |
| Trisodium phosphate (TSP) | 10-15% | Emulsifier, dispersant |
| Sodium bicarbonate (NaHCO₃) | 5-10% | pH buffer, mild cleaner |
| Non-ionic surfactant (e.g., NP-9) | 3-5% | Oil emulsification |
| Sodium sulfate (Na₂SO₄) | 5-10% | Filler, helps in dissolution |
| Chelating agent (EDTA) | 0.5-1% | Prevents scale formation |
| Wetting agent (Sodium dodecyl sulfate, SLS) | 1-2% | Improves wetting action |
Usage Instructions:
- Concentration: 10-25 g/L
- Temperature: 50-70°C
- Time: 5-15 minutes
- Application: Spray or immersion
2. Strong Alkaline Degreasing Powder (For Heavy-Duty Cleaning)
Application:
- Used for removing heavy grease, carbonized oil, and stubborn contaminants.
- Suitable for machinery parts, automotive cleaning, and industrial degreasing.
Formulation:
| Ingredient | % by Weight | Function |
|---|---|---|
| Sodium hydroxide (NaOH) | 20-30% | Strong alkalinity, grease breakdown |
| Sodium carbonate (Na₂CO₃) | 20-25% | pH buffer, helps emulsification |
| Sodium metasilicate (Na₂SiO₃) | 15-20% | Corrosion inhibitor, surface protection |
| Trisodium phosphate (TSP) | 10-15% | Oil emulsifier, detergent action |
| Sodium gluconate | 3-5% | Prevents scale formation, chelating agent |
| Non-ionic surfactant (NP-9 or NP-10) | 3-5% | Aids in oil removal |
| Anionic surfactant (Sodium Lauryl Sulfate – SLS) | 1-3% | Foaming and wetting agent |
| Sodium sulfate (Na₂SO₄) | 5-10% | Filler, helps dissolution |
| EDTA (Ethylenediaminetetraacetic acid) | 0.5-1% | Metal ion chelation |
Usage Instructions:
- Concentration: 15-40 g/L
- Temperature: 60-90°C
- Time: 10-20 minutes
- Application: Immersion or ultrasonic cleaning
Comparison Table:
| Property | Mild Degreaser | Strong Degreaser |
|---|---|---|
| Grease & Oil Removal | Light to Medium | Heavy-duty |
| pH Level | 9-11 | 12-14 |
| Corrosion Risk | Low | Higher (requires inhibitors) |
| Metal Compatibility | Mild Steel, Aluminum, Brass | Mild Steel, Cast Iron, Heavy Machinery |
| Temperature | 50-70°C | 60-90°C |
| Application | Spray & Immersion | Immersion & Ultrasonic |
These formulations can be customized based on specific industrial needs by adjusting surfactants and chelating agents.
