TECHNICAL STANDARD
ISO 8502-4
Preparation of steel substrates before application of paints and related products — Tests for the assessment of surface cleanliness — Part 4: Guidance on the estimation of the probability of condensation prior to paint application
ISO
Edition 2 / 2017
Current
WHAT DOES THIS STANDARD COVER?
Provides guidance for estimating the probability of condensation on a surface before paint application.
WHY IS IT RELEVANT?
Relevant to monitoring substrate temperature, air temperature, relative humidity and dew-point conditions before and during coating work. Project specifications and coating-manufacturer requirements govern acceptance.
KEY INSPECTION CONSIDERATIONS
ISO 8502-4 provides guidance for estimating the probability of condensation on a surface before paint application. Environmental inspection normally requires consideration of air temperature, surface temperature and relative humidity so that the dew-point temperature and the margin between surface temperature and dew point can be established. Environmental conditions can change during surface preparation and coating application. A single measurement should therefore not automatically be assumed to represent conditions throughout an entire work period. The applicable coating manufacturer requirements and project specification should be used to determine whether conditions are acceptable for the particular coating operation.
WHAT THE STANDARD SHOULD NOT BE USED TO ASSUME
ISO 8502-4 should not be interpreted as establishing one universal temperature or dew-point margin suitable for every coating product. Acceptable application conditions depend on the coating system, manufacturer requirements, project specification and site conditions. Relative humidity alone does not establish whether condensation is likely on the steel surface. Environmental readings should also not be treated as representative of locations or periods where conditions may differ significantly from the actual measurement location and time.
PRACTICAL INSPECTION APPLICATION
Environmental monitoring should be undertaken at locations representative of the coating work and at appropriate intervals during preparation and application activities. The inspector should record relevant environmental measurements and compare them with the coating manufacturer's application requirements and project specification. Particular attention may be required where conditions are changing rapidly, where steel temperatures differ from ambient conditions, or where work is being undertaken in enclosed, exposed or temperature-controlled environments.
RELATED TECHNICAL STANDARDS
RELATED TECHNICAL TOPICS
condensation; dew point; relative humidity; environmental monitoring; coating application
RELATED EXPERTISE
Coating Inspection; Technical Consultancy
ABOUT THIS TECHNICAL SUMMARY
Paint Inspection Ltd provides this information to help inspectors, engineers, asset owners and contractors understand the practical relevance of commonly referenced protective coatings standards. This page is PIL technical guidance and does not reproduce or replace the published standard. Users should refer to the current published standard, project specification, coating manufacturer requirements and other applicable contract documents when establishing project requirements or acceptance criteria.
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OFFICIAL STANDARD
PIL technical summaries are intended to explain the inspection relevance of industry standards and do not replace the published document.
STATUS AND SOURCE VERIFICATION
Edition and status checked against the official ISO catalogue in September 2026.