Overview
EN ISO 9717:2024 - Metallic and other inorganic coatings - Phosphate conversion coating of metals - specifies requirements and guidance for phosphate conversion coatings (phosphating) typically applied to ferrous materials, aluminium, zinc and their alloys. The 2024 edition supersedes EN ISO 9717:2017 and updates technical definitions, measurement methods and identification procedures. The standard covers the purpose of phosphate coatings (corrosion resistance, improved paint adhesion, cold-forming facilitation and friction modification) and defines how coatings should be specified, tested and documented.
Key topics and technical requirements
- Scope and designation: Defines coating types and a designation system (see Table 1) for classifying phosphate conversion coatings by composition and intended substrate.
- Information from purchaser: Lists mandatory details the purchaser must provide to the processor, including coating description, surface treatment details, sampling procedure, required appearance and corrosion resistance, and measures to minimize hydrogen embrittlement (noting special care for steels with tensile strength ≥ 1 000 MPa).
- Performance requirements:
- Appearance and surface condition expectations.
- Coating mass per unit area (area-related mass is emphasized in this edition).
- Post-treatment (sealants and other treatments) and their impact on corrosion performance.
- Correlation of coating mass and thickness - area-related mass replaces direct thickness measurement for more reliable specification.
- Heat treatment: Guidance on heat-treatment considerations, especially where hydrogen embrittlement is a risk.
- Test methods and annexes:
- Annex A (normative): Determination of coating resistance to neutral salt spray (ISO 9227 referenced).
- Annex B (informative): General information about substrate effects and process variables.
- Annex C (informative): Identification of phosphate coatings - updated to include nickel, and added analytical methods such as ICP and XRF for elemental analysis.
Practical applications
- Protecting and preparing metal surfaces prior to painting, powder coating or lubrication.
- Improving adhesion in automotive, aerospace, fasteners, wire drawing and general metal fabrication.
- Specifying corrosion resistance for components in adverse environments (often referenced in procurement and quality contracts).
- Designing phosphating processes and quality-control plans in surface‑treatment shops.
Who should use this standard
- Surface-treatment processors and pretreatment labs
- Coatings and corrosion engineers
- Purchasing/specification professionals and OEMs in automotive, aerospace, construction and metalworking
- Quality and compliance teams defining acceptance criteria and sampling plans
Related standards (normative references)
- ISO 2080 - Vocabulary for metallic and other inorganic coatings
- ISO 3892 - Determination of coating mass per unit area (gravimetric)
- ISO 4519 - Sampling procedures for inspection by attributes
- ISO 9227 - Salt spray tests
- ISO 9588 - Post-coating treatments to reduce hydrogen embrittlement
Keywords: EN ISO 9717:2024, phosphate conversion coating, phosphating, corrosion resistance, phosphating standard, phosphate coating, hydrogen embrittlement, area-related mass, salt spray test.
