BS EN ISO 11124 — Metallic Blast-Cleaning Abrasives for Steel Substrate Preparation Series

🎯 BS EN ISO 11124 is the British Standard series implementing EN ISO 11124 — specifications for metallic blast-cleaning abrasives for the preparation of steel substrates before application of paints and related products, identical to ISO 11124. The series classifies metallic blast-cleaning abrasives by type and specifies their grading, hardness, chemical composition, packaging, and lot-traceability requirements. It is the core basis for abrasive procurement and acceptance in steel-structure derusting and surface preparation. UK participation was entrusted to BSI committee STC/21 (Surface treatments and coatings), and the parts were also published as sections of BS 7079 Part E (E1 to E4), replacing earlier standards such as BS 2451:1963. The parent international work was prepared by ISO/TC 35 (Paints and varnishes), Subcommittee SC 12, Preparation of steel substrates before application of paints and related products.

1. Series Overview 📌

Before painting, steel surfaces must be stripped of mill scale, rust, and contaminants to the required cleanliness and roughness. Blast cleaning (or shot blasting) is one of the most common and economical methods, and the quality of the abrasive directly determines the cleaning result and the life of the subsequent coating. This series is organised by abrasive type: Part 1 gives a general introduction and classification (principles for metallic/non-metallic, shot/grit, and designation); Part 2 covers chilled-iron grit; Part 3 covers high-carbon cast-steel shot and grit; Part 4 covers low-carbon cast-steel shot. Each part specifies sieve grading (particle-size distribution), hardness (carbon content), shape, package marking, and lot traceability, and gives the correspondence between abrasive designations and common international standards. It should be noted that this series covers only metallic blast-cleaning abrasives; non-metallic abrasives (such as garnet, slag, and mineral products) are covered separately by the ISO 11126 series.

2. Structure of the Series 🧱

3. Part 1: General Introduction and Classification 🗂️

Part 1 establishes the basis for classifying and designating abrasives. Abrasives are divided into metallic (M) and non-metallic (NM) categories by material, and into shot (near-spherical) and grit (angular) by initial particle shape. Table 1 lists the commonly used metallic abrasives for steel substrate preparation, and Table 2 defines the initial particle shapes. The designation system combines material category, shape, and grade code into a single abrasive designation for procurement, acceptance, and traceability. The part also gives the correspondence between abrasive designations and commonly used international standards (such as SAE and JIS), facilitating cross-standard referencing.

• Classification codes: e.g., G (grit) and S (shot) denote shape, combined with the material code to form the complete designation.
• Corresponding standards: Annex A provides an index of international standards for metallic and non-metallic blast-cleaning abrasives.

4. Part 2: Chilled-Iron Grit Specification ⚙️

Chilled-iron grit is a common abrasive for removing heavy mill scale and old coatings because of its high hardness and moderate cost. Part 2 specifies its chemical composition (principally carbon, silicon, manganese, sulphur, and phosphorus), hardness, shape, and sieve-grading requirements, together with the cumulative retained (cumulative % retained) ranges for each grade so that the particle-size distribution is concentrated and uniform. Chilled-iron grit is hard and cleans quickly but tends to fracture and wear rapidly, so a balance must be struck between cleaning efficiency and abrasive life.

5. Part 3: High-Carbon Cast-Steel Shot and Grit Specification ⚙️

High-carbon cast-steel shot and high-carbon cast-steel grit have good toughness and wear resistance, making them among the most widely used metallic abrasives for blast and shot cleaning. Part 3 specifies the chemical composition, hardness, shape, and sieve-grading requirements for both the shot and the grit products, with separate grading tables for high-carbon cast-steel shot and high-carbon cast-steel grit. Compared with chilled-iron grit, high-carbon cast-steel products offer higher toughness and fatigue life and are well suited to recycling in closed-loop blast systems, giving a lower overall cost per unit area cleaned.

6. Part 4: Low-Carbon Cast-Steel Shot Specification ⚙️

Low-carbon cast-steel shot has a lower carbon content and even better toughness, and is mainly used where surface roughness and workpiece damage must be strictly controlled. Part 4 likewise specifies the chemical composition, hardness, shape, and sieve-grading requirements. Since this part is a scanned copy, the latest official edition should be consulted in practice. It is worth noting that ISO 11124-5 (cut steel wire) was planned to supplement the metallic-abrasive family with a finer specification.

7. Engineering Practice 🛠️

• Steel-structure derusting: select abrasive type and grading for the required surface cleanliness (e.g. Sa 2½, Sa 3) and roughness.
• Preparation before painting: control surface roughness and cleanliness to ensure coating adhesion and corrosion-protection life.
• Abrasive procurement acceptance: perform grading, hardness, chemical-composition, and impurity inspection per this series, and verify batch markings.
• Shot-blasting shop management: periodically replenish and screen abrasive, remove broken particles and dust, and maintain an effective proportion and grading.
• Safety and environment: when reclaiming metallic abrasive, pay attention to dust collection, noise, and fire/explosion management for metal dust.

8. Frequently Asked Questions ❓