ISO 13779-2:2018

Overview

ISO 13779-2:2018 - "Implants for surgery - Hydroxyapatite - Part 2: Thermally sprayed coatings of hydroxyapatite" specifies material and characterization requirements for single-layer thermally sprayed hydroxyapatite (HA) coatings applied to metallic surgical implants. The standard is primarily aimed at plasma-sprayed HA but can be used to characterize other thermal spray processes. It is not intended to replace internal operational controls and does not cover glass/glass-ceramic or other calcium‑phosphate coatings (e.g., α/β‑TCP, biphasic calcium phosphate).

Keywords: ISO 13779-2:2018, hydroxyapatite coatings, thermally sprayed, plasma sprayed, surgical implants, coating characterization, biocompatibility.

Key topics and technical requirements

• Scope: Requirements apply to single-layer thermally sprayed HA coatings; special considerations for thin coatings (<50 µm) and dual‑layer systems are noted.
• Material sourcing: Powders must conform to ISO 13779-6 and production test specimens should reflect actual implant manufacturing.
• Chemical composition:
  • Calcium to phosphorus (Ca:P) atomic ratio: 1.61 – 1.76 (measured per ISO 13779-3).
  • Trace elements / heavy metals: Maximum limits include As 3 mg/kg, Cd 5 mg/kg, Hg 5 mg/kg, Pb 30 mg/kg, and total heavy metals 50 mg/kg.
• Phase purity:
  • Sum of α‑TCP, β‑TCP and tetracalcium phosphate ≤ 30%.
  • CaO content ≤ 5%.
• Crystallinity: Crystallinity ratio ≥ 45% (ISO 13779-3 method).
• Morphology:
  • Thickness and tolerances assessed by ASTM F1854; roughness (Ra or Rt) per ISO 4288.
  • SEM or optical microscopy for porosity and cross‑sectional evaluation.
  • No universal thickness/roughness acceptance levels are set - these must be defined per implant design.
• Adhesion / coating strength:
  • Tensile (ISO 13779-4) or shear (ASTM F1044) testing as appropriate.
  • Mean adhesion strength ≥ 15 MPa and no single result < 10 MPa.
• Testing & reporting: Test methods, sampling, and test reports are specified; additional routine control tests may be necessary.

Applications

• Use ISO 13779-2:2018 to define product specifications, validate coating processes, and support regulatory submissions for orthopedic and dental implants with thermally sprayed HA coatings.
• Helps ensure biocompatibility, controlled dissolution/solubility behavior, and mechanical adhesion for osseointegration-promoting surfaces.
• Useful during supplier qualification, process change control, and failure/root‑cause analyses.

Who should use this standard

• Implant manufacturers and design engineers
• Medical device quality and regulatory teams
• Coating service providers and contract coaters
• Materials scientists and R&D groups developing HA coatings
• Notified bodies and testing laboratories verifying implant coating conformity

Related standards

• ISO 13779-3 (chemical analysis, crystallinity, phase purity)
• ISO 13779-4 (coating adhesion strength)
• ISO 13779-6 (HA powders)
• ISO 4288 (surface roughness)
• ASTM F1044, ASTM F1854 (shear testing, thickness/porosity evaluation)

ISO 13779-2:2018 is a practical reference for specifying and assessing thermally sprayed hydroxyapatite coatings on implants, balancing compositional, structural and mechanical requirements to support safe clinical performance.