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🛠 ISO 4042 Electroplated Coating Designations – Transition from Cr⁶⁺ to Cr³⁺ Systems

📘 Historical Standard (ISO 4042:1999 / ISO 4042:2000)

In earlier versions of ISO 4042, electroplated coatings were designated using a simple code format. A commonly used designation was:

A4E, where:

  • A = Zinc electroplated
  • 4 = Minimum coating thickness of 8 µm
  • E = Hexavalent chromium (Cr⁶⁺) passivation (typically yellow/iridescent chromate)

❗ Note: The “E” passivation used hexavalent chromium, which is now restricted under REACH (from September 2024) and RoHS (maximum 0.1% by weight in homogeneous materials).

📗 Updated Standard – ISO 4042:2022

The 2022 revision of ISO 4042 introduced a new modular format for specifying electroplated coatings, aligning with REACH and RoHS requirements. It replaces Cr⁶⁺ systems with safer Cr³⁺ (trivalent chromium) passivations.

✅ New Designation Format:

[Coating Metal][Thickness Code][Passivation Code][Topcoat Code]

Example: Zn8CnT2
This refers to:

  • Zn – Zinc electroplating
  • 8 – 8 µm coating thickness
  • Cn – Iridescent Cr³⁺ (trivalent) passivation
  • T2 – With sealant or topcoat

This is the recommended RoHS/REACH-compliant replacement for the withdrawn A4E coating designation.

✅ Trivalent Passivation Codes in ISO 4042:2022

CodeTypeAppearanceCr⁶⁺-FreeDescription
AnTransparentClear/BlueYesThin Cr³⁺ passivation, lower corrosion resistance
CnIridescantYellow/GoldYesThick Cr³⁺ passivation, high corrosion resistance
FnBlackBlackYesCr³⁺ black passivation, aesthetic & protective

⚠️ Why This Matters

  • Hexavalent chromium coatings like A4E are now prohibited under REACH (no authorisation after Sept 2024) and restricted under RoHS.
  • ISO 4042:2022 formally eliminates Cr⁶⁺-based systems and provides modular Cr³⁺-based alternatives.
  • When quoting or supplying plated fasteners, manufacturers must use updated Cr⁶⁺-free designations to ensure compliance and performance continuity.

Need help selecting a compliant coating for your application?
Our technical team at Hague Fasteners is here to help you specify safe, durable, and compliant solutions for your critical fastener requirements.