ISO 28199-2:2021

Overview

ISO 28199-2:2021 - part of the ISO 28199 series - defines laboratory methods to evaluate properties of coating systems related to the spray application process. It specifies how to determine colour stability / colour evaluation, process hiding power, re‑dissolving, overspray absorption, wetting, surface texture and mottling for coatings applied to a test panel under defined spray application conditions. The standard is intended for research, development, production control and failure analysis of paints and varnishes used in industrial and automotive spray processes.

Key topics and technical requirements

• Scope and test setup
  • Tests are carried out on test panels prepared according to ISO 28199-1 and use spray application with controlled film thickness ranges.
  • Results are evaluated primarily as functions of film thickness.
• Colour stability / colour evaluation
  • Colour space values (L*, a*, b*, C*, h) are plotted against film thickness to identify the film thickness range where colour is stable (plateau). The lowest (tmin) and highest (tmax) film thicknesses of stability are determined.
• Process hiding power
  • Evaluation of when a base coat fully covers the substrate by plotting colour/lightness versus film thickness and identifying the point at which a constant colour is achieved.
• Re‑dissolving
  • Detection of intercoat interaction where solvents in an applied clear coat affect the base coat; visualized as a drift out of the colour‑stability plateau (L25° and b25° are emphasized).
• Overspray absorption
  • Evaluated by comparing consecutive spraying stages; good absorption shows a smooth transition from colour stability to re‑dissolving.
• Wetting, surface texture and mottling
  • Surface texture evaluation includes limit values for long‑ and short‑wavelength textures (introduced in the 2021 revision).
  • Mottling assessment is separated into measurement techniques and visual evaluation in this edition.
• Reporting
  • Test report requirements and interpretation guidance are provided for reproducible quality assessment.

Practical applications and users

• Coating manufacturers and formulators - to optimize spray formulations for consistent colour and hiding power.
• Automotive OEMs and Tier suppliers - for quality control of base coats and clear coats in multi‑layer systems.
• Industrial coating applicators and process engineers - to validate spray processes, wetting behavior, and overspray handling.
• Test laboratories and R&D groups - for comparative testing, product development and root‑cause analysis of visual defects (mottling, texture, re‑dissolving).

Related standards

• ISO 28199-1:2021 - Vocabulary and preparation of test panels (normative reference)
• ISO 2808 - Film thickness measurement
• ISO 18314-1 - Colour measurement methods
• ISO 2813 - Gloss measurement

ISO 28199-2:2021 is a practical tool for assessing how coatings behave under spray application and for ensuring visual quality and process compatibility in industrial painting operations.