Phosphates & Corrosion Inhibitors
Sodium Molybdate
CAS 7631-95-0 — Non-Chromate Corrosion Inhibitor
Sodium molybdate is the preferred non-chromate corrosion inhibitor for cooling water systems, metalworking fluids, and engine coolants. Texas-Chem supplies industrial-grade sodium molybdate in bulk drums and totes.
CAS Number
7631-95-0
Formula
Na₂MoO₄
pH (1% solution)
9.0–10.0
Pack Sizes
Drums · Totes · Super Sacks
Structure
Na₂MoO₄ — Sodium Molybdate — CAS 7631-95-0
Safety & Regulatory
- NFPA Health
- 2 — Moderate hazard
- NFPA Flammability
- 0 — Non-flammable
- NFPA Reactivity
- 0 — Stable
- OSHA PEL (as Mo)
- 5 mg/m³
- DOT Hazard Class
- Not regulated
- Skin/Eye
- Irritant — wear gloves and safety glasses
Grades & Packaging
Available Grades
Pack Sizes
Also Known As
Physical & Chemical Properties
| CAS Number | 7631-95-0 |
| Molecular Formula | Na₂MoO₄ |
| Molecular Weight | 241.95 g/mol |
| Appearance | White crystalline powder |
| Solubility in Water | 56 g/100 mL at 20 °C |
| pH (1% solution) | 9.0–10.0 |
| Melting Point | 687 °C |
| Density | 3.28 g/cm³ |
| Molybdenum Content | ~39.7% as Mo |
| Corrosion Inhibition | Excellent — anodic inhibitor for steel |
| Toxicity | Low — preferred over chromate |
| Biodegradability | Not readily biodegradable |
Industrial Applications
Cooling Water Treatment
Sodium molybdate is used as a non-chromate corrosion inhibitor in cooling water systems, forming a protective molybdate oxide film on steel surfaces. It is the preferred replacement for sodium chromate in industrial cooling water programs.
Metalworking Fluids
Used as a corrosion inhibitor in water-based metalworking fluids, cutting fluids, and grinding fluids to protect ferrous metal workpieces and machine components from rust and corrosion.
Hydraulic Fluids
Used as a corrosion inhibitor in water-glycol hydraulic fluids for fire-resistant hydraulic systems in steel mills, die casting operations, and other high-temperature applications.
Engine Coolants
Sodium molybdate is used as a corrosion inhibitor in heavy-duty diesel engine coolants (NOAT/OAT formulations) for fleet and industrial engine applications, protecting steel and cast iron engine components.
Oilfield Water Treatment
Used in oilfield water injection systems to prevent corrosion of steel pipelines and injection well equipment in the Permian Basin and Gulf Coast.
Industrial Maintenance
Used in industrial maintenance cleaning and rust prevention formulations as a non-toxic corrosion inhibitor for ferrous metal surfaces.
Why Source Sodium Molybdate from Texas-Chem
- Industrial-grade sodium molybdate in stock — drums and totes
- Consistent quality with CoA on every lot
- Same-week delivery across Texas; nationwide LTL
- Technical support for cooling water and metalworking fluid applications
- One rep from first call to final delivery
Sodium Molybdate — Frequently Asked Questions
What is the difference between sodium molybdate and sodium chromate as corrosion inhibitors?▾
Both sodium molybdate and sodium chromate are anodic corrosion inhibitors that form a protective oxide film on steel surfaces. Sodium chromate provides excellent corrosion protection but is classified as a carcinogen (hexavalent chromium) and is heavily restricted under EPA and REACH regulations. Sodium molybdate provides comparable corrosion protection with much lower toxicity and is the preferred non-chromate replacement in cooling water and metalworking fluid applications.
What is the typical treat rate for sodium molybdate in cooling water?▾
Sodium molybdate is typically used at 50–200 ppm as molybdate (MoO₄²⁻) in cooling water systems. The treat rate depends on the system metallurgy, water chemistry, and target corrosion rate. Molybdate is often used in combination with azole copper inhibitors (BTA, TTA) and phosphate scale inhibitors for a complete cooling water treatment program. Contact Texas-Chem at 855-TEX-CHEM for cooling water treatment guidance.
Is sodium molybdate compatible with other corrosion inhibitors?▾
Yes. Sodium molybdate is compatible with most common corrosion inhibitors including azoles (BTA, TTA, MBT), phosphates (STPP, SHMP, zinc phosphate), nitrite, and organic inhibitors. It is commonly used in combination programs for synergistic corrosion protection. Verify compatibility with your specific formulation before use.
What is the difference between sodium molybdate and ammonium molybdate?▾
Sodium molybdate (Na₂MoO₄) is the preferred form for corrosion inhibitor applications due to its high solubility, neutral-to-alkaline pH, and compatibility with most water treatment programs. Ammonium molybdate ((NH₄)₂MoO₄) is used primarily in analytical chemistry and catalyst applications. For cooling water and metalworking fluid applications, sodium molybdate is the standard choice.