Overview
ISO 3711:1990 - "Lead chromate pigments and lead chromate‑molybdate pigments - Specifications and methods of test" - defines quality requirements and laboratory test methods for common lead chromate-based pigments used in paints and coatings. The standard classifies pigments by Colour Index (for example Pigment Yellow 34, Pigment Orange 21, Pigment Red 104), lists their approximate chemical identities, and distinguishes two product types: standard (type 1) and stabilized (type 2). The document replaces the 1976 edition and cross‑references general pigment test methods in the ISO 787 series.
Key topics and technical requirements
- Classification and identity
- Pigments are identified by Colour Index number and approximate composition (lead chromate, lead sulfochromate, lead chromate‑molybdate, etc.).
- Two types: standard (basic or normal lead chromates) and stabilized (contain additives to improve properties; vendor may be asked to declare nature and minimum lead content).
- Mandatory characteristics and limits (examples from the standard)
- Matter volatile at 105 °C - max 1% (m/m) (ISO 787‑2).
- Water‑soluble matter (cold extraction) - max 2% (m/m) (ISO 787‑8).
- Acidity/alkalinity of aqueous extract - measured in ml of 0.1 mol/l solution per 100 g - max 20 (ISO 787‑4).
- pH of aqueous suspension - 4 to 8 (ISO 787‑9).
- Residue on 45 µm sieve - max 0.3% (m/m) (ISO 787‑7).
- Lead content testing
- Two methods for total lead: a gravimetric method (specified as the referee method) and a titrimetric (electrolytic) method. Results are reported as % Pb or % PbO.
- Soluble lead extraction method is derived from ISO 6713:1984; limits and whether to test are agreed between parties.
- Reference and conditional requirements
- Colour, tinting strength, ease of dispersion, oil absorption and light fastness can be specified by agreement and tested using ISO 787 series methods.
Applications and users
- Intended for: pigment manufacturers, paint and coatings formulators, quality control and analytical laboratories, procurement/specification engineers, and regulatory/compliance bodies.
- Practical uses:
- Product specification and acceptance testing for lead chromate pigments.
- Quality control and batch release testing (total and soluble lead, particle size, pH, volatility).
- Supplier–purchaser agreements and dispute resolution (gravimetric method as referee).
- Ensuring consistent pigment performance in paints, inks and plastics where yellow/orange/red chromates are used.
Related standards
- ISO 787 series (general methods of test for pigments and extenders)
- ISO 842 (sampling)
- ISO 3856‑1 (soluble metal content methods)
- ISO 3696 (water for analytical use)
- ISO 6713 (soluble lead extraction reference)
Keywords: ISO 3711, lead chromate pigments, lead chromate‑molybdate, pigment specifications, methods of test, total lead content, gravimetric method, titrimetric method, Colour Index.
