ISO 11127-4:2020

Overview

ISO 11127-4:2020 specifies a simple, reproducible glass slide test to assess whether a non‑metallic blast‑cleaning abrasive attains a minimum hardness of 6 on the Mohs scale. It is a pass/fail test only (not a method for precise hardness measurement) and forms part of the ISO 11127 series of test methods for non‑metallic blast‑cleaning abrasives used in steel substrate preparation before painting and coating.

Key topics and requirements

• Purpose: Confirm whether an abrasive sample achieves at least Mohs hardness 6.
• Scope: Applies to non‑metallic blast‑cleaning abrasives; types and specific requirements are covered in the ISO 11126 series.
• Sampling: Use a representative sample in accordance with ISO 11127-1.
• Apparatus
  • Microscope with ×10 magnification.
  • Soda glass microscope slides with no observable scratches (borosilicate glass is unsuitable).
• Test procedure (summary):
  • Examine 5 g of material; if grains vary, select 5–10 grains of each colour/size.
  • Place selected grains between two soda glass slides.
  • Apply pressure and move one slide over the other in a reciprocating motion for 10 s.
  • If the glass surfaces show scratches after the test, the abrasive is considered to have a minimum hardness of Mohs 6.
• Test report must include:
  • Product identification (referencing the appropriate ISO 11126 part when applicable).
  • Reference to ISO 11127-4:2020, test result (pass/fail), any deviations, unusual observations, test date and tester identity.
• Limitations: This is a qualitative pass/fail screening; it does not provide accurate hardness values.

Practical applications and users

• Quality control and QA/QC labs in abrasive manufacturing and blasting service companies.
• Paint, coatings and surface preparation specifiers who need to verify abrasive suitability.
• Contractors and inspectors validating incoming batches of non‑metallic abrasives (e.g., garnet, olivine, slags).
• Procurement teams requiring simple acceptance tests to ensure abrasives meet minimum hardness to achieve effective blast cleaning and coating adhesion.

Benefits: fast, low‑cost screening to avoid soft abrasives that underperform, ensure consistency between batches, and support compliance with coating preparation specifications.

Related standards

• ISO 11127 series - Test methods for non‑metallic blast‑cleaning abrasives (sampling, particle size, moisture, chlorides, etc.).
• ISO 11126 series - Specifications and classification for non‑metallic blast‑cleaning abrasives.

Keywords: ISO 11127-4:2020, glass slide test, Mohs hardness 6, non-metallic blast-cleaning abrasives, abrasive testing, surface preparation, ISO 11126.