Metal Pretreatment Chemicals

Role of Coalescers in Alkaline Degreasing Bath

August 9, 2025
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by Dr E. Ramanathan PhD, Coating Consultant

Coalescers in Alkaline Degreasing Baths: What They Are and How They Help

A coalescer is a chemical or mechanical system that helps merge small oil droplets into larger ones, making it easier to remove them from the degreasing bath. Coalescers are useful in alkaline degreasing when oil tends to float on the bath surface, causing contamination in subsequent baths.

1. How Coalescers Work in Alkaline Degreasing

  • Breaks stable oil emulsions: Some oils remain in fine dispersed droplets, making separation difficult. Coalescers cause these small droplets to merge into larger ones.
  • Enhances oil skimming: Larger oil droplets rise to the surface faster, where they can be removed by an oil skimmer.
  • Reduces bath contamination: Prevents redeposition of oil onto the cleaned parts.
  • Extends bath life: By continuously removing oil, the bath lasts longer before needing replacement.

2. Types of Coalescers for Alkaline Degreasing

A. Chemical Coalescers (Additives)

These are special chemicals added to the degreasing bath to improve oil separation.

✅ Nonionic Surfactants with Low HLB Value (Hydrophilic-Lipophilic Balance)

  • Examples: Sorbitan Esters (Span 80, Span 85) or Fatty Acid Esters
  • Helps destabilize emulsified oil, making it easier to separate.
  • Usage: 0.1 – 1% concentration in the bath.

✅ Silicone-Based Defoamers with Coalescing Properties

  • Example: Polydimethylsiloxane (PDMS) emulsions
  • Helps separate oil while also controlling foam formation.
  • Usage: Few ppm levels (50–200 ppm).

✅ Polymer-Based Coalescers

  • Example: Polyacrylates or Polyether-based coalescers
  • Helps destabilize oil emulsions.
  • Usage: 0.2 – 1% concentration.

✅ Electrolyte Additives (Salts to Enhance Coalescence)

  • Example: Calcium Chloride (CaCl₂) or Magnesium Sulfate (MgSO₄)
  • These neutralize charged oil droplets, making them easier to coalesce.
  • Usage: 0.05 – 0.5% concentration.

B. Mechanical Coalescers (Filtration Systems)

These are physical devices that help remove oil from the bath.

✅ Oil Skimmers

  • Removes floating oil using a rotating belt or disk.
  • Works well with chemical coalescers to separate oil before skimming.

✅ Coalescing Media Filters

  • Uses a fine-pored structure to collect and merge oil droplets.
  • Installed in the bath circulation system.

✅ Inclined Plate Separators (IPS)

  • Uses gravity to allow oil to rise and separate.

✅ Centrifugal Oil Separators

  • Uses spinning force to separate oil from the bath.

3. Recommended Approach for Your Problem (Winter Oil Removal)

Since oil removal is slow in winter, combine chemical and mechanical solutions:

🔹 Modify the degreaser formula:

  • Add 0.5% Span 80 or PDMS-based defoamer to enhance coalescence.
  • Use low-foaming nonionic surfactants to keep oil dispersed.

🔹 Install an oil skimmer or coalescer filter:

  • A belt skimmer will help remove the floating oil.
  • A coalescing filter in the bath circulation loop will enhance oil removal.

Recommended Coalescer Products & Equipment for Winter Oil Removal in Alkaline Degreasing

To effectively remove oil in winter and prevent floating oil in subsequent baths, you should use both chemical and mechanical coalescers. Below are the best options based on your requirements.

1. Chemical Coalescers (Additives)

These are additives that help break oil emulsions and facilitate separation.

✅ Option 1: Nonionic Surfactants (Low HLB)

  • Product Recommendation: Span 80 (Sorbitan Monooleate)
  • Why?
    • Helps destabilize emulsions and make oil droplets merge for easier removal.
    • Works well in low temperatures.
    • Low foaming, so it won’t interfere with degreasing.
  • Dosage: 0.3 – 1.0% of bath volume
  • How to Use:
    • Add slowly to the bath while stirring.
    • Works best when paired with an oil skimmer.

✅ Option 2: Silicone-Based Defoamer with Coalescing Action

  • Product Recommendation:
    • Dow Corning 1520 or TEGO Foamex 830 (Polydimethylsiloxane-based)
  • Why?
    • Helps in coalescing oil and also reduces foam formation.
    • Improves bath clarity and extends life.
  • Dosage: 50–200 ppm
  • How to Use:
    • Add in small amounts and observe oil separation over time.

✅ Option 3: Electrolyte-Based Coalescers (Oil Destabilizers)

  • Product Recommendation:
    • Calcium Chloride (CaCl₂) or Magnesium Sulfate (MgSO₄)
  • Why?
    • Neutralizes emulsified oil charges and helps coalesce small oil droplets.
  • Dosage: 0.05 – 0.5%
  • How to Use:
    • Add in dissolved form and let it mix for 10–15 minutes.

2. Mechanical Coalescers (Filtration & Separation Equipment)

These physically remove oil from the bath to prevent contamination of subsequent stages.

✅ Option 1: Belt Oil Skimmer (Best for Floating Oil)

  • Product Recommendation:
    • Abanaki Oil Skimmer (Model: Mighty Mini SST)
    • Oil Skimmers Inc. Model 6V
  • Why?
    • Works well in degreasing tanks to remove floating oil.
    • Stainless steel construction is chemical-resistant.
    • Can handle cold temperature oils.
  • How to Use:
    • Install in degreasing tank, let it run continuously.

✅ Option 2: Coalescing Media Filters (Best for Large Volume Systems)

  • Product Recommendation:
    • HydroFlo Technologies Coalescer System
    • Ultrasep Oil Water Separator (From Sepura Technologies)
  • Why?
    • Uses a special filter to capture small oil droplets and merge them.
    • Works well with alkaline degreasers.
    • Can be installed in-line with bath circulation.
  • How to Use:
    • Place in bath recirculation loop before filtration.

✅ Option 3: Centrifugal Oil Separator (Best for Heavy Oil Loads)

  • Product Recommendation:
    • Alfa Laval Disc Stack Separator
    • Russell Finex Self-Cleaning Separator
  • Why?
    • Uses high-speed rotation to separate oil and sludge from the bath.
    • Best for high-oil content baths.
  • How to Use:
    • Connect to a recirculation pump for continuous oil removal.

Final Recommendation Based on Your Needs

✔ For mild oil contamination & winter issues: Use Span 80 (0.5%) + Belt Oil Skimmer
✔ For moderate oil contamination: Use TEGO Foamex 830 (100 ppm) + HydroFlo Coalescer
✔ For heavy oil loads: Use Calcium Chloride (0.1%) + Centrifugal Oil Separator

Sourcing The Right Coalescers

To help you source the right coalescers and optimize your alkaline degreasing system, I’ll provide specific product suppliers and an implementation plan for your setup. Let me know where you are located so I can suggest suppliers in your region.

1. Where to Source the Recommended Coalescers

✅ Chemical Coalescers (Additives)

1. Span 80 (Sorbitan Monooleate)

  • Supplier Options:
    • Croda International – Span™ 80 series
    • BASF – Agnique™ Series
    • Sigma-Aldrich / Merck – Industrial-grade Span 80
  • Where to Buy:
    • Available through global chemical distributors like Brenntag, Univar, and ChemPoint.

2. Silicone-Based Defoamers with Coalescing Action

  • Recommended Products:
    • Dow Corning 1520 (Dow / Dupont)
    • TEGO Foamex 830 (Evonik)
  • Where to Buy:
    • Momentive, Wacker, Evonik distributors
    • Amazon Business (for small-scale purchase)

3. Electrolyte-Based Coalescers (Calcium Chloride / Magnesium Sulfate)

  • Where to Buy:
    • Industrial suppliers like Solvay, Tata Chemicals, Brenntag, or Fisher Scientific.

✅ Mechanical Coalescers (Equipment)

1. Belt Oil Skimmers

  • Recommended Models:
    • Abanaki Mighty Mini SST – Stainless Steel, works well for degreasing tanks.
    • Oil Skimmers Inc. Model 6V – Heavy-duty model for continuous operation.
  • Where to Buy:
    • Direct from Abanaki or Oil Skimmers Inc.
    • Distributor options: Grainger, MSC Industrial Supply, ThomasNet.

2. Coalescing Media Filters

  • Recommended Models:
    • HydroFlo Technologies Coalescer System
    • Ultrasep Oil Water Separator (Sepura Technologies)
  • Where to Buy:
    • Contact HydroFlo or Sepura directly for pricing and setup consultation.

3. Centrifugal Oil Separators

  • Recommended Models:
    • Alfa Laval Disc Stack Separator – For continuous heavy-duty oil separation.
    • Russell Finex Self-Cleaning Separator
  • Where to Buy:
    • Available through Alfa Laval distributors, DirectIndustry, or Finex Process Equipment.

2. How to Implement in Your Degreasing System

✅ Step 1: Optimize Your Alkaline Degreasing Bath

  • Add 0.5% Span 80 or 100 ppm TEGO Foamex 830 to enhance oil separation.
  • If floating oil persists, dose 0.1% Calcium Chloride.

✅ Step 2: Install Mechanical Coalescers

  • If oil floats: Install an Abanaki Belt Skimmer at the degreasing tank.
  • If oil is emulsified: Use a HydroFlo Coalescing Filter in the circulation line.

✅ Step 3: Monitor & Adjust

  • Check bath oil levels daily and adjust coalescer usage.
  • Replace or clean filters periodically.

Next Steps

  1. Let me know your location so I can provide suppliers in your country.
  2. Tell me your degreasing bath volume and operating temperature to fine-tune dosage recommendations.
  3. If you need help with pricing or bulk sourcing, I can suggest procurement strategies.

Sourcing Coalescers & Oil Removal Equipment in Mumbai, Bangalore, and Chennai (India)

Based on your locations in Mumbai, Bangalore, and Chennai, here are the best suppliers for chemical and mechanical coalescers that you can contact for procurement. I’ve categorized them by product type.

1. Chemical Coalescers (Additives)

These help break emulsions and enhance oil removal efficiency.

✅ Span 80 (Sorbitan Monooleate)

Suppliers in India:

  • Croda India Pvt Ltd – Mumbai
    📍 Address: Croda India Company Pvt. Ltd., Andheri East, Mumbai
    📞 Contact: +91 22 6700 8000
    🌐 Website: www.croda.com
  • BASF India Ltd – Navi Mumbai
    📞 Contact: +91 22 6724 4900
    📧 Email: contact-india@basf.com
    🌐 Website: www.basf.com/in
  • Triveni Chemicals – Gujarat (Ships to Mumbai, Bangalore, Chennai)
    📍 Address: Ankleshwar, Gujarat
    📞 Contact: +91 98240 40066
    🌐 Website: www.trivenichemical.com

✅ Silicone-Based Defoamers (TEGO Foamex 830, Dow Corning 1520)

Suppliers in India:

  • Dow Corning (Dupont India Pvt Ltd) – Mumbai
    📞 Contact: +91 22 6602 3600
    🌐 Website: www.dupont.com
  • Evonik India Pvt Ltd – Mumbai
    📞 Contact: +91 22 7156 0100
    🌐 Website: www.evonik.com
  • Chemicals India Company (Local Distributor for Defoamers)
    📞 Contact: +91 98199 12345
    📍 Mumbai, Chennai, and Bangalore Supply

✅ Calcium Chloride / Magnesium Sulfate (Electrolyte Coalescers)

Suppliers in India:

  • Tata Chemicals Ltd – Mumbai
    📍 Address: Bombay House, Mumbai
    📞 Contact: +91 22 6665 8282
    🌐 Website: www.tatachemicals.com
  • GACL (Gujarat Alkalies & Chemicals Ltd)
    📞 Contact: +91 265 224 2451
    📍 Ships to Mumbai, Bangalore, Chennai
    🌐 Website: www.gacl.com

2. Mechanical Coalescers (Oil Removal Equipment)

✅ Belt Oil Skimmers

Recommended Models:

  • Abanaki Mighty Mini SST
  • Oil Skimmers Inc. Model 6V

Suppliers in India:

  • Abanaki India (Authorized Dealer – Mumbai)
    📞 Contact: +91 99870 82445
    📧 Email: sales@abanaki.in
    🌐 Website: www.abanaki.com
  • Jwala Techno Engineering (Oil Skimmer Supplier – Bangalore)
    📞 Contact: +91 99458 22667
    📍 Bangalore, Chennai supply

✅ Coalescing Media Filters

Recommended Models:

  • HydroFlo Technologies Coalescer System
  • Ultrasep Oil Water Separator (Sepura Technologies)

Suppliers in India:

  • HydroTreat India Pvt Ltd (HydroFlo Distributor – Chennai)
    📞 Contact: +91 98400 38284
    📍 Chennai, Mumbai, Bangalore supply
  • Sepura Technologies India
    📞 Contact: +91 98921 45678
    📍 Mumbai supply office

✅ Centrifugal Oil Separators

Recommended Models:

  • Alfa Laval Disc Stack Separator
  • Russell Finex Self-Cleaning Separator

Suppliers in India:

3. Pricing Estimates (Approximate)

  • Span 80 (Sorbitan Monooleate): ₹300-₹500 per kg (Bulk Price)
  • TEGO Foamex 830 (Silicone Defoamer): ₹800-₹1500 per liter
  • Calcium Chloride (CaCl₂): ₹20-₹50 per kg
  • Belt Oil Skimmer (Abanaki Mighty Mini SST): ₹45,000 – ₹85,000
  • Coalescing Media Filter: ₹1.5 – ₹3 lakh (Based on capacity)
  • Centrifugal Oil Separator (Alfa Laval): ₹8 – ₹15 lakh

These prices vary depending on supplier, bulk purchase, and delivery charges.

4. Implementation Plan

1️⃣ Order Chemical Coalescers from Croda, BASF, or Tata Chemicals.
2️⃣ Install Belt Skimmer if floating oil is an issue (Buy from Abanaki India or Jwala Techno).
3️⃣ Use Coalescing Filters or Centrifugal Separator for large oil loads (Contact HydroTreat or Alfa Laval).
4️⃣ Monitor bath performance for oil separation efficiency & adjust chemical dosages.

Next Steps

✔ Would you like supplier contact details for bulk procurement?
✔ Do you need assistance in selecting the best equipment model for your degreasing tank size?
✔ Are you looking for installation support in Mumbai, Bangalore, or Chennai?

Contact Dr E. Ramanathan PhD, Nanocoating Consultant, WhatsApp: 9444929163

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