ISO 14921:2010

Overview

ISO 14921:2010 - "Thermal spraying - Procedures for the application of thermally sprayed coatings for engineering components" - specifies a general, process-oriented procedure for applying thermally sprayed coatings to enhance surface properties or to reclaim worn/non‑conforming parts. The standard defines selection criteria, process steps and inspection points but does not prescribe detailed methods for every application because of the wide variety of materials, component geometries and performance requirements.

Key topics and requirements

ISO 14921:2010 covers the complete workflow for thermal spraying, including:

• Pre‑inspection and repair assessment
  • Verify component geometry, concentricity, existing defects and previous coatings before preparation.
• Substrate and coating design considerations
  • Assess substrate suitability, fatigue and strength impacts, accessibility and maximum allowable coating thickness.
• Preliminary machining
  • Remove worn profiles, avoid sharp edges, and perform concentric machining where required; degreasing when necessary.
• Masking and contamination control
  • Use masking resistant to grit blasting and spraying; prevent contamination during all stages.
• Surface preparation
  • Grit blasting is the normal method; preparation must follow EN 13507 or agreed alternatives.
• Thermal spraying execution
  • Spray as soon as possible after preparation, control temperature to avoid overheating or condensation, minimize dust entrapment; operator qualification per ISO 14918 is recommended.
• Post‑spray activities
  • Inspection (visual per ISO 14923 and thickness measurement), optional sealing (follow supplier instructions), finishing (turning, milling, grinding; see ISO 14924), and final inspection for dimensions, roughness and defects.
• Documentation
  • Maintain a record of the applied spray procedure and inspection results (Annex C example).

Important exclusions: ISO 14921 does not apply to thermally sprayed zinc/aluminum coatings for atmospheric corrosion protection (see ISO 2063) or to fused self‑fluxing alloy coatings (see ISO 14920).

Applications and practical value

ISO 14921 is valuable for specifying and controlling thermally sprayed coatings used to:

• Restore worn components or reclaim parts to dimensional tolerance
• Improve surface performance (wear resistance, corrosion resistance, electrical/thermal conductivity, friction control)
• Define inspection points and documentation requirements to support quality management

Following ISO 14921 helps ensure repeatable coating application, reduced rework, and clearer supplier–client agreements on process parameters and acceptance criteria.

Who should use this standard

• Coating specifiers and engineers
• Maintenance and repair workshops
• Quality managers and inspectors
• Thermal spray operators and process planners
• Procurement professionals preparing coating specifications

Related standards

• ISO 14923 - characterization and testing of thermally sprayed coatings
• ISO 14918 - thermal spray operator qualification
• ISO 14920 - fused self‑fluxing alloy coatings
• ISO 2063 - thermal spraying of zinc/aluminium for corrosion protection
• EN 13507, EN 15520, EN 657 - supporting guidance on pre‑treatment, design and terminology

Keywords: ISO 14921:2010, thermal spraying, thermally sprayed coatings, coating procedures, surface preparation, sealing, inspection, repair of engineering components.