ISO 8502-3 is the international standard used to assess the quantity and size of dust particles on steel surfaces prepared for painting. Ensuring a surface is "dust-free" is critical because even invisible particles can cause coating failure, blistering, or poor adhesion.
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
The chart rates dust from Class 0 (cleanest) to Class 5 (dirtiest) based on a visual comparison: Class 0: No dust visible under 10x magnification.
Class 1: Very slight amount of dust; particles are far apart.
Class 2: Small amount of dust; particles are visible but sparse.
Class 3: Moderate amount of dust; clearly visible to the naked eye.
Class 4: Significant amount of dust; covers a large portion of the tape.
Class 5: Dense dust layer; the surface is completely covered. Particle Size Classes
In addition to quantity, the standard categorizes the size of the particles found: Class 0: Particles not visible under 10x magnification.
Class 1: Particles visible only under 10x magnification (less than 0.05mm). Class 2: Particles 0.05mm to 0.15mm in diameter. Class 3: Particles 0.15mm to 0.25mm in diameter. Class 4: Particles 0.25mm to 0.50mm in diameter. Class 5: Particles larger than 0.50mm. Why the "Updated" PDF Matters
Recent updates to industry best practices (often referenced in NAVSEA or NORSOK standards) emphasize that a Class 2 Quantity and Class 2 Size are typically the maximum allowable limits for high-performance immersion coatings (like tank linings).
⚠️ Key Reminder: The official ISO 8502-3 chart is a copyrighted document. While summary PDFs are available from equipment manufacturers (like Elcometer or TQC Sheen), the actual visual comparison must be done using high-quality printed masters to ensure accuracy. To help you get exactly what you need, let me know:
Do you need to know the specific requirements for a certain industry (e.g., Marine or Oil & Gas)?
Are you trying to find a supplier for the official test kits?
The current version of the standard is ISO 8502-3:2017 , which replaced previous editions like the 1992 version. This standard provides a qualitative, pressure-sensitive tape method to assess the quantity and size of dust remaining on blast-cleaned steel surfaces before painting. iTeh Standards ISO 8502-3 Dust Level Classifications The assessment is divided into two primary metrics: Quantity Rating Size Class iTeh Standards Particle Size Description Particle Diameter No particles visible under 10x magnification Visible under 10x magnification, not by naked eye Just visible with normal/corrected vision Clearly visible with normal/corrected vision Large particles clearly visible Very large particles clearly visible Quantity Rating (1–5): iso 85023 dust level chart pdf updated
Determined by comparing the tape sample to pictorial references that show the density of dust coverage. Common Acceptance Criteria: Many painting specifications require a maximum Quantity Rating 2 Size Class 2 for high-performance coatings. Rösler Group The Critical Role of ISO 8502-3 in Surface Preparation Introduction
Surface preparation is widely regarded as the most critical stage in any industrial coating project. While visible contaminants like rust and mill scale are often the primary focus, microscopic "invisible" threats like residual dust can be equally devastating to a coating's lifespan. ISO 8502-3 provides the standardized framework necessary to detect and quantify these particles using a simple yet effective pressure-sensitive tape method. ISO - International Organization for Standardization The Impact of Dust on Coating Integrity
Residual dust on blast-cleaned steel acts as a "bond-breaker" between the substrate and the protective coating. Even a thin layer of microscopic particles can reduce adhesive strength, leading to premature delamination or blistering. Furthermore, dust is often hygroscopic; it can trap moisture against the steel, accelerating corrosion under the paint film, often before the asset even enters service. ISO - International Organization for Standardization INTERNATIONAL STANDARD ISO 8502-3
Understanding ISO 8502-3 Dust Level Chart
The ISO 8502-3 standard provides a method for assessing the cleanliness of surfaces in terms of dust and other contaminants. The standard is part of the ISO 8502 series, which focuses on the preparation of steel substrates before applying paints and related products.
What is the ISO 8502-3 Dust Level Chart?
The ISO 8502-3 dust level chart is a visual guide used to classify the dust levels on steel surfaces. The chart provides a reference for assessing the cleanliness of surfaces, which is crucial in ensuring the adhesion and performance of coatings.
Dust Levels According to ISO 8502-3
The ISO 8502-3 standard defines the following dust levels:
| Dust Level | Description | Visual Comparison | | --- | --- | --- | | A | No dust | No visible dust | | B | Light dust | A few small dust particles | | C | Medium dust | Some dust particles, but no continuous coverage | | D | Heavy dust | Continuous coverage of dust particles |
Updated Standards: What You Need to Know
The ISO 8502 series was updated in 2017, and the new standards bring some changes to the dust level classification. Here are the key updates:
ISO 8502-3:2017 Dust Level Chart PDF
You can find the updated ISO 8502-3:2017 standard and the dust level chart in PDF format on the International Organization for Standardization (ISO) website or through other online resources. ISO 8502-3 is the international standard used to
Key Takeaways
Download the ISO 8502-3:2017 PDF
You can download the ISO 8502-3:2017 PDF from the following sources:
Please note that you may need to purchase a copy of the standard or have a subscription to access the PDF.
ISO 8502-3 standard is a critical benchmark in industrial coating, specifically designed to assess residual dust on cleaned steel surfaces before painting. Even after rigorous abrasive blasting, microscopic dust particles can remain, acting as a barrier that prevents proper paint adhesion and traps moisture, which leads to premature corrosion, peeling, and flaking. The Mechanics of the "Tape Test"
The standard utilizes a qualitative "pressure-sensitive tape method". A strip of specialized adhesive tape—typically 200 mm long—is pressed onto the prepared steel surface. Pressure is applied either manually with a thumb or, for greater accuracy in disputes, using a calibrated spring-loaded roller to ensure consistent force. Once removed, the tape is mounted on a contrast-colored board (usually black or white) for visual evaluation. Understanding the ISO 8502-3 Rating Chart The evaluation is split into two distinct categories: Particle Size INTERNATIONAL STANDARD ISO 8502-3
Marta stared at the blinking cursor on her screen. The subject line read: URGENT: ISO 85023-3:2025 Dust Level Chart Updated.
She rubbed her tired eyes. As a coatings inspector for offshore wind farms, the ISO 85023 standard was her bible. It dictated how to measure and report dust on steel surfaces before painting. The "dust level chart" — those grainy black-and-white reference photographs of dust particles (sizes 1 through 5) — was her most-used tool.
Her phone buzzed. It was Jan, the lab manager.
“Did you see the email?” Jan’s voice was tight. “The new charts are live. They’ve changed Size 3.”
“Changed how?” Marta asked, her stomach dropping. A change to a middle-tier dust level meant every single inspection report she’d filed in the last six months might need re-evaluation.
“The particle density,” Jan said. “The old chart showed Size 3 as scattered particles under 10x magnification. The new update—ISO 85023-3:2025—has revised the micrograph. Size 3 now shows clusters. Which means our current ‘acceptable’ threshold for turbine tower internals is now a ‘reject’.”
Marta pulled up the PDF. It loaded slowly, a watermark reading AUTHORIZED REVISION across its header. She compared the old scanned copy on her hard drive to the new official PDF.
Old Size 3: ten distinct, isolated specks. New Size 3: three dense clusters, like tiny galaxies. The new standard introduces a more detailed classification
“This is a disaster,” she whispered. “We have a turbine blade shipment leaving Rotterdam tomorrow. I signed off on it yesterday using the old chart.”
There was a pause. “That’s why I called,” Jan said. “The client’s quality manager just downloaded the new PDF. He’s asking why our certificate doesn’t match the current standard.”
Marta minimized the PDF and opened her field notes. She remembered that turbine. The steel had looked clean, but there had been a faint, shadowy haze in one corner. Under the old rules, it was a Size 2.5—acceptable. Under the new updated chart, with its stricter clustering definition, it was a clear Size 3. Reject.
She zoomed in on the new chart’s footnote, which she hadn't noticed before. It read: “Note 4: This revised chart supersedes all previous photographic references. Retroactive application is advised for critical assets.”
Retroactive. The word felt like a hammer.
“We have to ground the shipment,” Marta said, her voice steady now. “I’ll re-inspect tonight with the new PDF on my tablet. We’ll blast that section again.”
“That’s three days of delay,” Jan sighed. “The client will invoice us for liquidated damages.”
“Better than a coating failure five years from now,” Marta replied. “The chart doesn’t lie, Jan. It’s been updated for a reason. Someone, somewhere, had a delamination because of old Size 3 dust. We’re not going to be that someone.”
She hung up and saved the new PDF to her offline folder: ISO_85023_Dust_Chart_2025_OFFICIAL.pdf.
Then she grabbed her hard hat. The offshore wind might wait, but dust never did.
I understand you’re looking for a document on ISO 8502-3 (often confused with a non-existent “ISO 85023”), which is the standard for assessing dust levels on steel surfaces before coating. There is no ISO 85023 — the correct reference is ISO 8502-3:2017 (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).
Below is a full, ready-to-use technical paper that includes the updated dust level chart, interpretation guide, and practical application. You can copy this directly.
Since you are searching for the ISO 8502-3 dust level chart PDF updated, let’s describe exactly what that chart contains until you can download the official copy.
The chart is divided into two main assessment axes:
ISO 8502-3 Dust Deposit Assessment — Updated Guide & Dust Level Chart (PDF)