Boiler — Process Challenge

Boiler Scale Prevention: Antiscalants & Dispersants

Residual feedwater hardness deposits CaCO3/CaSO4 and silica on boiler tubes, insulating them and risking overheating. Design uses a phosphonate plus a polymer dispersant and chelants to sequester hardness as soluble complexes
Updated Jun 2026
Solution Approach

RawSource supplies the base chemicals that go into these programs. We can help with product selection, grade matching, and sourcing from multiple origins for supply security.

Typical Treatment Workflow
1
Water & System Assessment
Characterize the water and the system — hardness, alkalinity, pH, TDS/conductivity, microbial load, and the metallurgy and temperatures of the equipment being protected.
2
Program & Chemistry Selection
Match coagulants, flocculants, scale and corrosion inhibitors, biocides, or pH adjusters to the water profile and discharge limits, factoring compatibility with any existing program.
3
Jar Testing & Dosing
Confirm coagulant and flocculant dose and feed point by jar test, set inhibitor and biocide treat rates, and size packaging (drums, totes, bulk) to consumption.
4
Monitoring & Control
Track residuals, turbidity, ORP, corrosion coupons, and effluent compliance, adjusting chemistry and dose as feedwater and load change.
Recommended Chemistries (5)
Hydroxyethylidene Diphosphonic Acid
CAS 2809-21-4
Phosphate Esters & Derivatives
Primary CaCO3 scale inhibitor
HEDP threshold-inhibits CaCO3/CaSO4 and is thermally stable enough for low/medium-pressure boiler service, keeping hardness from nucleating on tubes
Melting Point: 198-199   Boiling Point: 578.8   Solubility: 1.15e+01 g/L
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Polyacrylic Acid Sodium (PAAS)
CAS 9003-04-7
Polymers & Resins
Conditioning
Polyacrylate disperses precipitated hardness and iron oxide as a mobile sludge that leaves with blowdown rather than baking onto the tube
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Sodium Polyaspartate (PASP)
CAS 55719-33-0
Acids & Salts
pH Adjustment
Biodegradable polyaspartate inhibits and disperses CaCO3/CaSO4/silica scale; a greener dispersant option. (Spine tags pH Adjustment; chemistry is scale inhibition.)
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Ethylenediaminetetraacetic Acid
CAS 60-00-4
Amines & Amides
Broad-spectrum chelant
EDTA forms soluble 1:1 chelates with Ca2+/Mg2+/Fe, dissolving residual hardness so it cannot precipitate on heat-transfer surfaces
Melting Point: 237 °C   Density: 0.86 at 20 °C   Solubility: 1000000 mg/L at 25 °C
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DTPA (Diethylenetriaminepentaacetic Acid)
CAS 67-43-6
Amines & Amides
High-performance chelant for iron
Higher-denticity chelant holds iron and hardness through higher temperatures than EDTA, backstopping the program at elevated boiler pressure
Physical Description: White to off-white solid   Boiling Point: Decomposes   Melting Point: 219-220 ºC
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