ASTM B842-23 PDF

Overview

ASTM B842-23: Standard Specification for Electrodeposited Coatings of Zinc Iron Alloy Deposits establishes the requirements and guidelines for applying electrodeposited zinc-iron alloy coatings on metal substrates. Developed by ASTM International, this standard specifies coating composition, methods of preparation and treatment, essential attributes of the deposit, and inspection protocols. The use of only SI units ensures measurement consistency. This standard promotes corrosion protection and functional performance of coated metal parts in diverse industries, aligning with international guidelines for global trade and materials engineering.

Key Topics

• Coating Composition and Classes

  • One class is defined: approximately 99% zinc with the balance as iron.
  • Two types of chromate conversion finishes are recognized:
    • Type A: Black chromate conversion coating.
    • Type B: Iridescent yellow chromate conversion coating.
  • Three coating thickness grades: 6 μm, 12 μm, and 18 μm.

• Surface Preparation

  • The substrate must be meticulously cleaned and prepared according to referenced standards to ensure strong adhesion and reliable corrosion resistance.
  • Only basis metal free from detrimental flaws is suitable for coating.

• Performance Requirements

  • Coating must be uniform, adherent, and free from surface defects such as blisters, pits, or cracks.
  • Minimum coating thickness must be maintained across all significant surfaces as specified.
  • The standard outlines requirements for appearance, adhesion, and corrosion resistance.

• Testing and Inspection

  • Specifies accepted test methods for thickness (magnetic, X-ray, microscopical, coulometric), adhesion, and corrosion resistance.
  • Sampling plans for inspection are based on mutually agreed methods or referenced ASTM standards.
  • Special test specimens may be designated if required.

• Hydrogen Embrittlement Prevention

  • Pre- and post-coating treatments for high-strength steels are detailed to minimize hydrogen embrittlement risk, critical for structural or load-bearing components.

Applications

ASTM B842-23 is widely used for providing corrosion-resistant zinc-iron alloy coatings on various metal components, with particular relevance in:

• Automotive Industry

  • Fasteners, brackets, and structural parts exposed to harsh conditions often utilize zinc-iron coatings to extend lifespan and resist corrosion, especially where additional forming or bending operations occur post-coating.

• Electrical and Electronics

  • Metal connectors and housings that demand a controlled, corrosion-resistant surface.

• General Manufacturing

  • Hardware, tools, and metal fittings requiring a durable yet cost-effective protective coating.

• Construction and Infrastructure

  • Components where enhanced corrosion resistance and consistent surface appearance are necessary for reliability and aesthetics.

Zinc-iron alloy coatings offer an optimal balance between cost, performance, and process versatility, meeting demanding functional and regulatory requirements across sectors.

Related Standards

ASTM B842-23 works alongside several referenced and related ASTM standards, including:

• ASTM B117 - Practice for Operating Salt Spray (Fog) Apparatus, for corrosion testing
• ASTM B183, B242, B320, B322 - Practices and guides for preparing various steel substrates and cleaning metals before electroplating
• ASTM B374 - Terminology relating to electroplating
• ASTM B487, B499, B504, B568 - Measurement methods for coating thickness
• ASTM B571 - Practice for qualitative adhesion testing of metallic coatings
• ASTM B849, B850 - Guidelines for reducing the risk of hydrogen embrittlement in steel parts
• ASTM D3951 - Practice for commercial packaging

Adherence to these connected standards ensures comprehensive control over the coating process, product quality, and safety, supporting best practices in metal finishing and surface protection.