Rutile TiOâ Grades for Coatings: How to Select the Right One
Why Grade Selection Matters
Titanium dioxide is the single most expensive raw material in most coating formulations, accounting for 15-30% of total raw material costs. Selecting the wrong grade wastes money and compromises performance. The three variables that matter most are: production process, surface treatment chemistry, and particle size distribution.
In a typical architectural coating at 20% PVC, switching from chloride-process rutile ($2,600/MT) to high-quality sulfate-process rutile ($2,300/MT) saves ~$60/MT of paint. For a 10,000 MT/year plant, that's $600,000 in annual savings — if the coating spec allows it.
Sulfate vs Chloride Process Rutile
|
Parameter |
Sulfate Process |
Chloride Process |
|
TiOâ‚‚ Purity |
92-94% |
95-97% |
|
Particle Size Dist. |
Broader (CV 35-45%) |
Narrower (CV 25-35%) |
|
Gloss Potential |
70-85 units (60آ°) |
85-95+ units (60آ°) |
|
Dispersion |
Moderate — more dispersant needed |
Superior — easier wet-out |
|
Cost Premium |
Baseline |
+15-25% |
|
Best For |
Architectural, industrial, primers |
Automotive, coil, high-gloss |
Choose chloride when: gloss >85 units required, or minimum film thickness is critical. Choose sulfate when: coating is matte/satin (>60 units), interior application, or cost priority.
How Surface Treatment Affects Performance
Without surface treatment, TiOâ‚‚ would degrade the binder system under UV.
Silica (SiO₂) coating — Dense encapsulation maximizing weatherability. Best for: exterior architectural and automotive. Provides 2-3x better chalk resistance in QUV testing vs non-silica grades.
Alumina (Al₂O₃) coating — Improves dispersion and reduces agglomeration. Best for: high-gloss systems. Standard on most sulfate-process rutile.
Zirconia (ZrO₂) coating — Highest chemical durability. Best for: coil coatings, aggressive industrial environments.
Organic after-treatment — Polyols or siloxanes for specific resin systems. Best for: solvent-based and high-speed dispersion.
"Do not compare TiOâ‚‚ grades by TiOâ‚‚ content alone. A 93% grade with dense silica coating can outperform 95% with minimal coating in outdoor durability. The surface treatment is often more important than core purity."
Selecting by Coating Type
|
Coating Type |
Process |
Treatment |
Grade Examples |
|
Interior Architectural |
Sulfate |
Alumina |
R-251, R-2196 |
|
Exterior Architectural |
Sulfate/Chloride |
Silica+Alumina |
DR-2588, CR-758 |
|
Automotive OEM |
Chloride |
Advanced multi-layer |
CR-758, CR-718 |
|
Industrial/Anti-Corrosion |
Sulfate/Chloride |
Zirconia or Silica |
DR-2589, R-2196 |
|
Marine |
Chloride |
Dense Silica |
CR-758, CR-718 |
|
Powder Coating |
Sulfate |
Alumina (heat-stable) |
R-251 |
Detailed Recommendations
Interior Architectural — Sulfate-process rutile with alumina coating (R-251, R-2196). UV resistance minimal. Priority: cost-effective opacity. TiO₂ 92-94%, L* ≥94.
Exterior Architectural — Dual-coated rutile (DR-2588, CR-758). Expect 8-12 years color retention in moderate climates with proper formulation.
Automotive — Chloride-process only (CR-758, CR-718). Requires 90+ gloss units and extreme UV durability. Price premium justified.
Industrial — Zirconia-treated grades preferred for chemical resistance. Typical TiO₂ loading in primers: 12-18% vs 20-25% in topcoats.
Marine — Dense silica encapsulation grades only. 20-30% premium over architectural grades, but repaint cycle extends from 5-7 to 10-15 years.
Powder Coatings — Verify thermal stability at 180-200آ°C curing. Not all rutile grades are heat-stable.
6 Key Quality Parameters for Coatings
- TiO₂ Content (%)— ≥92% (sulfate), ≥94% (chloride).
- Rutilization Rate (%)— Target ≥98%. Lower = incomplete calcination = reduced opacity.
- Dispersion (Hegman)— High-gloss: ≥7.5 Hegman (≤10خ¼m). Matte: ≥6.0 Hegman (≤20خ¼m).
- Oil Absorption (g/100g)— Lower (16-20) allows higher pigment loading. Affects CPVC directly.
- Residue on 45خ¼m Sieve (%)— Premium ≤0.02%, Standard ≤0.05%.
- Relative Scattering Power— Target ≥100 (premium), ≥95 (standard) per ISO 591-1.