ISO 11124-2:2018

Overview

ISO 11124-2:2018 sets the international standard for chilled-iron grit abrasives used in blast-cleaning processes for preparing steel substrates before the application of paints and related coatings. This specification defines 12 distinct grades of chilled-iron grit based on particle size ranges and includes essential technical requirements such as hardness, density, defect limits, and chemical composition. The standard ensures consistency and quality for abrasives supplied in their new condition, making it a critical reference for manufacturers, suppliers, and users of metallic blast-cleaning abrasives.

Chilled-iron grit is primarily used in both static and on-site blasting equipment, with a particular focus on situations where recycling and reusing the abrasive material are possible. While ISO 11124-2 was developed targeting steel surface preparation, its principles and properties are applicable to other materials treated through blast-cleaning techniques per ISO 8504-2.

Key Topics

• Grade Designations and Particle Size:

  • The standard identifies chilled-iron grit abrasives with the designation "Abrasive ISO 11124 M/CI/G" followed by a numeric grade code.
  • This grade corresponds to the nominal particle size in hundredths of millimeters (e.g., G100 = 1.00 mm).
  • Twelve grades are defined, each specifying cumulative percentage retained on specific sieve mesh apertures ensuring precise particle size control.

• Mechanical and Physical Requirements:

  • Hardness: At least 90% of particles must have a hardness above 650 HV, providing the grit with high abrasion capability.
  • Apparent Density: Minimum density is specified at 7.0 kg/dm³ to guarantee effectiveness during blast cleaning.
  • Particle Shape: Must be predominantly angular grit, with limitations on round particles or shot (max 10%).

• Defect and Structural Requirements:

  • Limits are imposed on internal defects such as voids (max 10%), shrinkage defects (max 10%), and cracks (max 40%).
  • Total defective particles must remain below 40% of the sample.
  • Microstructure must predominantly consist of white iron type with iron carbide in martensite; free graphite or ferrite must be less than 5% per particle.

• Chemical Composition and Moisture Content:

  • Carbon content: Minimum 1.7% mass fraction ensures the abrasive’s optimal hardness and durability.
  • Moisture: Maximum allowable moisture is 0.2% mass fraction to prevent corrosion and degradation during storage.

• Packaging and Traceability:

  • Detailed labelling with product designation including particle shape and grade is mandatory.
  • Traceability information is recommended at pallet, drum, or box levels for quality control and supply chain accountability.

Applications

• Surface Preparation for Coatings: Chilled-iron grit abrasive plays a vital role in preparing steel substrates by removing rust, mill scale, and old coatings before painting or protective coating applications.
• Industrial Blast Cleaning: The abrasives are widely used in heavy industry sectors including shipbuilding, infrastructure maintenance, metal fabrication, and automotive manufacturing.
• Reusable Abrasives: Suitable for facilities with abrasive recovery systems, chilled-iron grit maintains consistent performance over multiple blast cycles, supporting sustainable practices.
• Various Materials: While optimized for steel substrates, the grit abrasives are also suitable for preparing other materials requiring surface roughness and cleanliness for coating adhesion.

Related Standards

• ISO 11124 Series: This document is Part 2 of ISO 11124, which specifies metallic blast-cleaning abrasives. Other parts cover additional types of abrasives and related parameters.
• ISO 11125 Series: Defines test methods for metallic blast-cleaning abrasives including sampling, particle size distribution, hardness, density, defect evaluation, foreign matter content, and moisture determination.
• ISO 8504-2: Details the blast-cleaning techniques applicable to steel and other surfaces, complementing the abrasive specifications in ISO 11124-2.
• ISO 9556: Covers the determination of total carbon content in steel and iron, a relevant chemical test referenced for chill-iron grit abrasives.

Keywords: ISO 11124-2, chilled-iron grit, blast-cleaning abrasives, steel surface preparation, particle size grading, abrasive hardness, metallic abrasive specifications, abrasive defect limits, blast cleaning standards, reusable abrasives, paint substrate preparation, ISO metallic abrasives standards.