Dr E. Ramanathan PhD
Formulations of Trication phosphating chemical
Formula-1
A trication phosphating chemical formulation (zinc–nickel–manganese based) suitable for room temperature application (25–35°C) can be formulated as follows (for 100 L of working bath solution):
NOTE: This formulation is intended for platers or phosphaters who want to do in-house phosphating in the tank directly.
Trication Phosphating Chemical – Working Bath Composition
| Component | Chemical | Approx. Concentration (g/L) | Purpose |
|---|---|---|---|
| Phosphoric Acid (85%) | H₃PO₄ | 8–12 | Source of phosphate ions |
| Zinc Salt | Zinc nitrate Zn(NO₃)₂ | 1.0–1.5 | Zinc cation source |
| Nickel Salt | Nickel nitrate Ni(NO₃)₂ | 0.3–0.5 | Nickel cation source (coating enhancer) |
| Manganese Salt | Manganese nitrate Mn(NO₃)₂ | 0.3–0.5 | Manganese cation source (coating toughness) |
| Nitrate (accelerator) | Sodium nitrate (NaNO3) | 1.0–2.0 | Increases reactivity |
| Surfactant (non-ionic) | Wetting agent | 0.1–0.3 | Improves surface wetting |
| Water | Demineralized water | Balance to 100 L | Medium |
Bath Parameters
- Temperature: Room temperature (25–35°C)
- pH: 2.8 – 3.5
- Treatment Time: 5–15 minutes
- Free Acid (FA): ~1.0–1.5 points
- Total Acid (TA): ~10–15 points
- FA/TA Ratio: 1:10 to 1:12
Notes
- Use pure, analytical-grade or technical-grade chemicals.
- Monitor the bath regularly for FA and TA using titration.
- Add boosters to replenish phosphate and metal content as required.
- Ideal for steel, zinc-coated steel, and galvanized parts.
Formula-2
Stock Concentrate Version – nitrite free
Here is a trication phosphating stock concentrate formulation to prepare 100 L of stock solution, which can be diluted 1:10 with water to prepare the working bath.
Trication Phosphating Stock Concentrate (for 100 L)
| Component | Chemical | Quantity (kg or L) | Purpose |
|---|---|---|---|
| Phosphoric Acid (85%) | H₃PO₄ | 25.0 kg | Main source of phosphate |
| Zinc Nitrate (Zn(NO₃)₂·6H₂O) | Zinc nitrate hexahydrate | 4.0 kg | Source of Zn²⁺ |
| Nickel Nitrate (Ni(NO₃)₂·6H₂O) | Nickel nitrate hexahydrate | 1.2 kg | Source of Ni²⁺ |
| Manganese Nitrate (Mn(NO₃)₂·4H₂O) | Manganese nitrate tetrahydrate | 1.2 kg | Source of Mn²⁺ |
| Sodium Nitrate | NaNO3 | 2.0 kg | Accelerator |
| Surfactant (non-ionic) | Wetting agent (e.g., NP-10) | 0.3 – 0.5 kg | Surface wetting |
| Deionized Water | — | To make up 100 L | Solvent |
Dilution for Working Bath:
- Dilution Ratio: 1 part stock + 9 parts demineralized water
- Example: To make 100 L of working bath, mix 10 L of stock with 90 L of water.
Storage & Handling Notes:
- Use HDPE or acid-resistant storage tanks.
- Stir thoroughly during preparation.
- Store in a cool, dry place away from sunlight.
- Regularly analyze TA, FA, and metal ion concentrations in working bath.
Phosphate formulation live sheets
Trication phosphating chemical – Saitech Informatics
Formula – 3
Trication Phosphating (Zn/Mn/Ni) – Two-Pack Concentrate Formula with Nitrite
For iron and steel surfaces – suitable for corrosion resistance and paint adhesion
Pack A: Phosphating Concentrate
(Base: Phosphate source, accelerators, metal ions)
| No | Raw Material | Function | Quantity (kg / 100 L) |
|---|---|---|---|
| 1 | Zinc phosphate (Zn₃(PO₄)₂·4H₂O) | Main phosphate source | 8.0 |
| 2 | Manganese carbonate | Mn²⁺ source | 3.0 |
| 3 | Nickel carbonate | Ni²⁺ source | 2.0 |
| 4 | Orthophosphoric acid (85%) | Acidity & phosphate balance | 20.0 |
| 5 | Sodium dihydrogen phosphate | Buffer, additional phosphate source | 5.0 |
| 6 | Surfactant (non-ionic type) | Wetting and surface activity | 1.0 |
| 7 | DM Water | Solvent | Q.S. to 100.0 L |
Pack B: Accelerator / Additive Pack (Nitrite Based)
(To be added just before dilution and use)
| No | Raw Material | Function | Quantity (kg / 10 L) |
|---|---|---|---|
| 1 | Sodium nitrite (NaNO₂) | Accelerator | 2.0 |
| 2 | Surfactant (optional) | Foaming control | 0.2 |
| 3 | DM Water | Solvent | Q.S. to 10.0 L |
Dilution & Usage:
- Typical bath concentration:
- Pack A: 3–5% v/v
- Pack B: 0.3–0.5% v/v
- pH: 4.2–4.8 (adjust with phosphoric acid or ammonia)
- Operating temp: 45–55 °C
- Time: 5–10 min
- Free acid: 1.0–1.8 pts
- Total acid: 20–30 pts
- Fe²⁺ control: <1.0 g/L (oxidize if needed)
NOTE:
In nitrite accelerator pack formulations for trication phosphating, the surfactant must be:
- Non-ionic
- Low-foaming
- Stable in acidic and oxidizing environments
- Compatible with sodium nitrite
✅ Recommended Surfactants:
| Surfactant Name | Type | Function in Nitrite Pack | Dosage (%) |
|---|---|---|---|
| Alphox 200 | Non-ionic (ethoxylated nonylphenol) | Wetting, improves film uniformity | 0.2–0.5 |
| Dobanol 91-6 | Non-ionic (alcohol ethoxylate) | Low-foam, acid-stable | 0.2–0.4 |
| Triton X-100 | Non-ionic (octylphenol ethoxylate) | Surface wetting | 0.1–0.3 |
| Renex 60 | Non-ionic (castor oil ethoxylate) | Good stability with nitrite | 0.2–0.4 |
| Pluronic L62 or L64 | Block copolymer (EO/PO) | Very low foaming, acid compatible | 0.1–0.2 |
Note: Avoid anionic surfactants like SDS or sulphonates in the nitrite pack, as they may react with nitrite or destabilize the bath.
Why anionic surfactant not recommended in nitrite accelerator pack
Anionic surfactants (e.g., SDS, SLS, sodium lauryl sulfonate) disturb nitrite accelerator packs used in trication phosphating due to the following chemical and physical reasons:
⚠️ 1. Redox Instability (Chemical Degradation)
- Sodium nitrite (NaNO₂) is an oxidizing agent.
- Anionic surfactants, especially those with unsaturated hydrocarbon chains or sulfonate groups, can undergo oxidation, leading to:
- Decomposition of the surfactant
- Loss of nitrite content over time
- Generation of noxious nitrous gases (e.g., NO, NO₂)
⚠️ 2. Complex Formation
- Sulfonate groups in anionic surfactants may complex with metal ions (Zn²⁺, Ni²⁺, Mn²⁺), disrupting:
- Phosphate crystal nucleation
- Uniformity of coating
- Accelerated sludge formation
⚠️ 3. Excessive Foaming
- Many anionic surfactants have high foam indices.
- In spray phosphating or recirculation systems, foam:
- Disrupts spray uniformity
- Leads to pump cavitation
- Reduces coating quality
⚠️ 4. pH Drift
- Some anionic surfactants alter pH buffering, especially in acidic formulations, affecting:
- Bath stability
- Phosphate grain size
- Deposition rate
✅ Preferred: Non-Ionic Surfactants
They remain stable in oxidizing, acidic media, and do not interfere with metal phosphating reactions.
Formula – 4
Trication Phosphating (Zn/Mn/Ni) – Single-Pack Concentrate Formula with Nitrate or Chlorate Accelerator
Used for iron and steel phosphating with built-in oxidizer
Single-Pack Concentrate (100 L Batch Basis)
| No | Raw Material | Function | Quantity (kg) |
|---|---|---|---|
| 1 | Zinc oxide | Zn²⁺ source | 4.0 |
| 2 | Manganese carbonate | Mn²⁺ source | 2.0 |
| 3 | Nickel carbonate | Ni²⁺ source | 1.5 |
| 4 | Orthophosphoric acid (85%) | Phosphate & pH control | 18.0 |
| 5 | Sodium dihydrogen phosphate | Buffer, phosphate stabilization | 5.0 |
| 6 | Sodium nitrate or Sodium chlorate | Accelerator (oxidizer) | 2.5 (nitrate) or 1.5 (chlorate) |
| 7 | Surfactant (non-ionic, low foam) | Wetting, spreading | 1.0 |
| 8 | Sequestering agent (EDTA/Glucamate) | Prevent sludge, metal control | 0.5 |
| 9 | Antifoam (optional) | Foam suppression | 0.2 |
| 10 | DM Water | Solvent | Q.S. to 100.0 L |
Usage Parameters:
- Dilution ratio: 4–6% v/v in demineralized water
- Temperature: 45–55 °C
- Time: 5–8 min
- pH: 4.2–4.8
- Free acid: 1.0–1.5 pts
- Total acid: 20–30 pts
- Sludge control: Use mechanical agitation or periodic filtering
- Bath life: Monitor Fe²⁺, replenish with concentrate or adjust pH if needed
Formula – 5
Trication Phosphating – Spray Application Formula (Single Pack, with Nitrate/Chlorate Accelerator)
Designed for use in multistage spray phosphating lines with low sludge formation and high coverage
Single-Pack Concentrate for Spray (100 L Batch Basis)
| No | Raw Material | Function | Quantity (kg) |
|---|---|---|---|
| 1 | Zinc oxide | Zn²⁺ source | 3.0 |
| 2 | Manganese carbonate | Mn²⁺ source | 1.5 |
| 3 | Nickel carbonate | Ni²⁺ source | 1.0 |
| 4 | Orthophosphoric acid (85%) | Phosphate & pH control | 12.0 |
| 5 | Sodium dihydrogen phosphate | Buffer, phosphate balance | 4.0 |
| 6 | Sodium nitrate or Sodium chlorate | Accelerator (oxidizer) | 2.0 (nitrate) or 1.2 (chlorate) |
| 7 | Surfactant (non-ionic, low foaming) | Wetting, uniform film formation | 0.8 |
| 8 | Chelating agent (EDTA or NTA) | Prevent sludge, improve bath stability | 0.5 |
| 9 | Antifoam (silicone-based, low dose) | Control foaming in spray systems | 0.1 |
| 10 | DM Water | Solvent | Q.S. to 100.0 L |
Operating Conditions – Spray Process
- Dilution ratio: 3–5% v/v in demineralized water
- Spray pressure: 1.0–1.5 bar
- Spray temperature: 45–55 °C
- Spray time: 2–3 minutes per stage
- pH (bath): 4.2–4.6
- Free acid: 1.0–1.5 pts
- Total acid: 18–25 pts
- Fe²⁺ limit: <0.8 g/L
- Sludge tendency: Very low (ensure filtration in circulation system)
Formula 6
Low-Zinc Eco-Friendly Trication Phosphating – Spray Application (Single Pack)
Designed for energy-efficient spray lines, low zinc discharge, and high paint adhesion; suitable for OEMs/ancillaries aiming for RoHS/REACH compliance
Eco Trication Phosphating Concentrate – 100 L Batch
| No | Raw Material | Function | Quantity (kg) |
|---|---|---|---|
| 1 | Zinc oxide | Low zinc source (reduced Zn²⁺) | 1.5 |
| 2 | Manganese carbonate | Mn²⁺ source for crystal structure | 2.0 |
| 3 | Nickel carbonate | Ni²⁺ source for fine grain coating | 0.8 |
| 4 | Orthophosphoric acid (85%) | Main phosphate source, pH control | 10.0 |
| 5 | Sodium dihydrogen phosphate | Buffer phosphate, coating uniformity | 3.5 |
| 6 | Sodium nitrate or chlorate | Accelerator (oxidizer) | 2.0 (nitrate) or 1.2 (chlorate) |
| 7 | Polyhydroxycarboxylic acid (e.g., gluconic acid or citric acid) | Complexing, eco sludge control | 1.5 |
| 8 | Non-ionic surfactant (low foam) | Surface wetting, uniform deposition | 0.8 |
| 9 | Antifoam agent (silicone-free) | Foam control in spray systems | 0.1 |
| 10 | DM Water | Solvent | Q.S. to 100.0 L |
Recommended Bath Conditions
- Dilution: 3–5% v/v
- Temperature: 45–55 °C
- Spray time: 2–3 minutes
- pH: 4.3–4.6
- Free acid: 1.0–1.3 points
- Total acid: 16–22 points
- Zinc concentration (in bath): ~0.2–0.4 g/L
- Sludge tendency: Minimal (complexed form)
- Eco compliance: RoHS/ELV/REACH-friendly
Advantages
- Up to 60% reduction in zinc usage
- Low sludge = less maintenance
- Suitable for high-speed spray phosphating lines
- Compatible with e-coat and powder coatings
- Can be paired with nano-sealers or chrome-free passivation for enhanced corrosion resistance
Bath Maintenance Schedule + MSDS Format
For Low-Zinc Eco Trication Spray Phosphating Solution (Nitrate/Chlorate-Based)
✅ A. Bath Maintenance Schedule
| Task | Frequency | Method/Notes |
|---|---|---|
| pH Check | Daily (2× shift) | Use calibrated pH meter. Maintain 4.3–4.6 |
| Free Acid Titration | Daily | Maintain 1.0–1.3 pts (Titrate with 0.1N NaOH) |
| Total Acid Titration | Daily | Maintain 16–22 pts (Titrate with phenolphthalein) |
| Zinc Content | 2× per week | AAS or colorimetric method. Maintain 0.2–0.4 g/L |
| Iron Contamination (Fe²⁺) | 2× per week | Keep <0.8 g/L. Oxidize with H₂O₂ or replace bath |
| Sludge Removal | Weekly | Clean tank bottom or filter line sump |
| Filtration Check | Weekly | Check inline filters, clean or replace |
| Makeup Addition | As needed | Add concentrate if pH/acidity drops, based on titrations |
| Spray Nozzles Inspection | Weekly | Check for clogging; clean or replace |
📄 B. MSDS (Summary)
1. Product Identification
- Product Name: Eco Trication Spray Phosphating Concentrate
- Form: Liquid concentrate
- Use: Phosphate coating on ferrous metals before painting
2. Hazard Identification
- Hazards: Mildly acidic. Irritant to eyes and skin.
- PPE Required: Gloves, safety goggles, apron
- First Aid:
- Eyes: Rinse with water for 15 min
- Skin: Wash with soap and water
- Inhalation: Move to fresh air
- Ingestion: Do not induce vomiting. Seek medical help
3. Composition
| Ingredient | % w/w (approx) | CAS No. |
|---|---|---|
| Orthophosphoric acid | 10–12% | 7664-38-2 |
| Zinc oxide | 1.5% | 1314-13-2 |
| Manganese carbonate | 2.0% | 598-62-9 |
| Nickel carbonate | 0.8% | 3333-67-3 |
| Sodium nitrate/chlorate | 2.0 / 1.2% | 7631-99-4 / 7775-09-9 |
| Surfactants & organics | 2–3% | – |
| Water | Balance | 7732-18-5 |
4. Handling & Storage
- Store in plastic drums in a ventilated area
- Avoid contact with alkalis
- Shelf life: 6 months (sealed)
5. Spillage & Disposal
- Neutralize with soda ash
- Collect and dispose as per local pollution control norms
- Avoid discharge into water bodies
Technical Articles
What is Trication Phosphating? – Saitech Informatics
Prerequisites for Trication phosphating – Saitech Informatics
SOP for Trication phosphating intended for ED coating – Saitech Informatics
NOTE
This standard trication phosphating formulation is not suitable for galvanized iron (GI) substrates. GI has a zinc-rich surface that reacts aggressively with acidic phosphate solutions, leading to:
- Excessive zinc dissolution
- Heavy sludge formation
- Poor or powdery coating
- Uneven or non-adherent phosphate layers
Recommended Approach for GI (Galvanized Iron):
- Use a Zinc Phosphate formulation with mild acceleration (low free acid, low total acid).
- Or preferably use a specialized GI-compatible phosphating system, such as:
- Titanium/Zirconium-based nanoceramic pretreatment (Cr-free)
- Calcium-modified zinc phosphate (low FA/TA ratio)
- Selective fluoride-accelerated phosphate system with buffering
