Overview - EN ISO 3892:2001 (ISO 3892:2000)
EN ISO 3892:2001 specifies gravimetric methods for determining the coating mass per unit area of conversion coatings on metallic materials. It covers phosphate and chromate conversion coatings on common substrates (iron/steel, zinc, cadmium, aluminium and their alloys). The standard describes required apparatus, sample preparation, reagents and dissolution procedures to measure coating mass by weight loss after chemical or electrolytic removal.
Key topics and technical requirements
- Scope and limitations
- Applies only to conversion coatings without supplementary films (oils, polymers, wax).
- Results are mean mass per unit area for the measured area and do not reveal local bare spots or spot thickness variation.
- Apparatus
- Glass or suitable vessel for dissolution.
- Analytical balance capable of 0.1 mg resolution.
- Electrical equipment for electrolytic dissolution (required for some chromate coatings).
- Test-piece sizing
- Maximum mass 200 g. Table 1 specifies minimum total surface areas by expected coating mass (examples from the standard: ≤1 g/m2 → 400 cm2; >1–10 g/m2 → 200 cm2; >10–25 g/m2 → 100 cm2; >25–50 g/m2 → 50 cm2; >50 g/m2 → 25 cm2).
- To target an overall measurement uncertainty of 5%, surface areas should be measured to within 1%.
- Reagents and procedures (by coating type)
- Manganese and iron phosphates: immersion in 50 g/L chromium(VI) oxide at 75 °C (repeated until mass stabilizes).
- Zinc phosphate: hot alkaline EDTA/triethanolamine solution.
- Phosphate on zinc/cadmium: ammonium dichromate in ammoniac (room temperature).
- Crystalline phosphate on aluminium: nitric acid (hot or room temperature options).
- Chromate on zinc/cadmium: cyanide/NaOH solution with cathodic electrolytic dissolution (graphite anode recommended).
- Chromate/amorphous phosphate on aluminium: dilute nitric acid for fresh coatings; molten sodium nitrate/sodium hydroxide mixtures for aged coatings.
- Safety
- The standard includes warnings: many reagents are hazardous (chromium VI, cyanide, molten salts). Use fume cupboards, PPE and follow local regulations.
- Results
- Mass-per-unit-area calculated from weight loss and area; includes guidance on measurement uncertainty.
Applications and users
- Used by metal finishing and surface-treatment laboratories, OEM quality-control (automotive, aerospace, electronics), industrial coaters, and materials testing labs to:
- Verify compliance with product or procurement specifications.
- Perform supplier acceptance testing and process control.
- Benchmark conversion-coating mass for corrosion protection performance.
Related standards
- Prepared by ISO/TC 107 (Metallic and other inorganic coatings). EN ISO 3892:2001 supersedes EN ISO 3892:1994 and corresponds to ISO 3892:2000.
Keywords: EN ISO 3892:2001, conversion coatings, gravimetric methods, coating mass per unit area, phosphate coatings, chromate coatings, metallic materials, analytical balance, surface treatment.
