Dust on a prepared surface acts as a bond-breaker between the primer and the steel substrate. It can also absorb moisture, leading to osmotic blistering under the paint film. The ISO 8502-3 standard standardizes how inspectors sample, visually evaluate, and record dust contamination before any coating application begins. The Pressure-Sensitive Tape Test Method
The specification for the coating project will typically state the maximum permissible dust quantity grade and size rating. For example, a project specification may state, "Maximum dust quantity: Grade 2 per ISO 8502-3."
Imagine a critical bridge construction project where every detail matters. The lead inspector,
An official, updated ISO 8502-3 chart evaluates dust using two primary metrics: and Particle Size Class . 1. Dust Quantity Rating (0 to 5) iso 85023 dust level chart pdf updated
The standard classifies the size of the dust particles using letters:
This classification system allows inspectors to characterize the typical particle size present on the test surface, which directly influences the potential impact on coating performance.
Trace amounts; particles visible only under magnification. Rating 2: Dust barely visible to the naked eye. Rating 3: Particles clearly visible. Rating 4: Significant dust accumulation; easily noticeable. Rating 5: Heavy contamination. 2. Dust Size Classes (0–5) Dust on a prepared surface acts as a
A "Class 3" dust level with fine particles (<100 µm) might be acceptable for a pipe coating in a dry climate, but the same Class 3 with coarse particles (300 µm) is an automatic failure for any high-performance coating.
Because ISO standards are copyrighted intellectual property, the official, fully updated ISO 8502-3 document and its visual comparison charts must be acquired through authorized channels:
Note: Any overall discoloration of the tape (such as reddish-brown from steel grit or black from slag) must automatically be recorded as a Quantity Rating 5. 2. Dust Particle Size Classes (0 to 5) the surface must be re-cleaned
The test uses a specific pressure-sensitive adhesive tape that is pressed onto the steel and then transferred to a display card for comparison against a visual rating scale. The 5 Levels of Dust Quantity
If the test results show a high dust quantity, the surface must be re-cleaned, often using clean and dry compressed air, and re-tested.
The industry standard for assessing this contamination is ("Preparation of steel substrates before application of paints and related products - Tests for the assessment of surface cleanliness - Part 3: Assessment of dust on steel surfaces prepared for painting (pressure-sensitive tape method)"). This guide provides a detailed breakdown of the standard, how to use the ISO 8502-3 dust level chart , and where to find the updated PDF resources for 2026. What is the ISO 8502-3 Standard?
The standard was majorly updated in , which replaced the older 1992 version. The updated standard clarifies testing procedures, establishes rigorous parameters for the pressure-sensitive tape, and standardizes visual assessment templates to reduce human subjectivity. 2. The Core Metric: Dust Quantity Ratings (0–5)