Overview
ISO 591-1:2000 - "Titanium dioxide pigments for paints - Part 1: Specifications and methods of test" defines requirements and analytical methods for titanium dioxide (TiO2) pigments used in paints. The standard covers classification, required characteristics, sampling and two validated test methods for determining TiO2 content. It is intended for quality control, procurement and laboratory testing in the paints and coatings supply chain.
Key topics
- Classification
- Two pigment types: Type A (anatase) and Type R (rutile).
- Five grades: A1, A2, R1, R2, R3 with differing purity and performance expectations.
- Essential requirements
- Titanium dioxide content (mass % minimums):
- A1: 98%, A2: 92%
- R1: 97%, R2: 90%, R3: 80%
- Matter soluble in water (max % by mass): ranges by grade (e.g., A1 0.6%, A2 0.5%, R3 0.7%).
- Residue on 45 μm sieve: ≤ 0.1% (by mass).
- Appearance: soft, dry powder or readily crushed to that state.
- Conditional requirements
- Colour, scattering power, oil absorption, pH of aqueous suspension and moisture after preconditioning may be specified by agreement between parties.
- Sampling
- Representative sampling per ISO 15528 is required.
- TiO2 content test methods
- Method A - Aluminium reduction method (suitable for individual and routine analysis): sample dissolution in sulfuric acid + ammonium sulfate, reduction of Ti(IV) to Ti(III) with aluminium under CO2 atmosphere, titration with ammonium iron(III) sulfate using ammonium thiocyanate indicator. Determinations are carried out in duplicate and results reported to 0.1%.
- Method B - Chromium(II) chloride / zinc amalgam reduction: automatable and suitable for routine high-throughput analysis.
- Reporting
- Test report content and calculation conventions are specified (e.g., mean of duplicate determinations).
Applications and users
- Paint and coatings manufacturers - incoming raw-material QC and batch release testing.
- Pigment producers - product specification and compliance verification.
- Independent testing laboratories - routine and referee analyses for contractual disputes.
- Procurement and specifications authors - to define supplier requirements and acceptance criteria.
- Regulatory bodies and certification schemes - referencing standardized test methods and limits.
Related standards
Keywords: ISO 591-1, titanium dioxide pigments, TiO2 content test, anatase, rutile, paint pigments, aluminium reduction method, chromium(II) chloride method, pigment specifications, quality control.
