Zinc-5 % Aluminum-Mischmetal Alloy-Coated Steel Wire Strand

A855/A855M: Standard Specification for Zinc-5 % Aluminum-Mischmetal Alloy-Coated Steel Wire Strand

For engineers and designers working with critical infrastructure and demanding environmental conditions, specifying the right materials is paramount. ASTM A855/A855M provides an authoritative framework for selecting high-performance steel wire strand, ensuring reliability and longevity in challenging applications. This industry-leading standard is an essential resource for professionals seeking robust corrosion resistance and superior mechanical properties.

What is A855/A855M?

ASTM A855/A855M is a comprehensive standard specification that defines requirements for zinc-5% aluminum-mischmetal (Zn-5 Al-MM) alloy-coated steel wire strand. Originating from ASTM's commitment to material excellence, its primary purpose is to ensure the production of durable, corrosion-resistant wire strand suitable for demanding structural applications. This standard is crucial for guaranteeing consistent performance and quality in the materials used for vital infrastructure components.

Scope & Purpose

This standard governs the manufacture and properties of five distinct grades of Zn-5 Al-MM alloy-coated steel wire strand. It specifies requirements for the base steel, the composition and application of the Zn-5 Al-MM coating, and the mechanical properties of the finished strand, including minimum breaking strengths and elongation. The scope covers strand intended for use as guys, messengers, span wires, and similar applications where superior corrosion resistance and formability are critical. It does not cover the installation procedures or the design of the supporting structures themselves.

Who Must Comply?

• • Primary audience: Materials Engineers, Wire Mill Operators, Quality Control Inspectors, Project Engineers, and Purchasing Agents.
• • Industries affected: Utilities (power and telecommunications), Civil Engineering, Infrastructure Development, and Manufacturing.
• • Compliance nature: Voluntary, but often a de facto mandatory requirement for projects specifying high-performance, corrosion-resistant materials.
• • Enforcement: Compliance is typically verified through material certifications, third-party testing, and project-specific quality assurance programs.

Key Requirements Overview

The standard requires that the base steel used for the wire strand be of high quality, manufactured through commercially accepted processes. Professionals must ensure that the Zn-5 Al-MM alloy coating meets specific chemical composition limits, as defined by ASTM B750, to guarantee its protective properties. Key provisions include detailed specifications for the five different grades of strand (Utilities, Common, Siemens-Martin, High-strength, and Extra high-strength), each with defined minimum breaking strengths and elongation requirements. Furthermore, the standard mandates adherence to specific coating weights, categorized into Class 1 and Classes A, B, and C, to ensure adequate corrosion protection for the intended service life.

Related Standards & References

ASTM A855/A855M works in conjunction with several other ASTM standards to provide a complete material specification. ASTM A90/A90M is essential for verifying the weight of the Zn-5 Al-MM alloy coating, a critical factor in its protective capability. ASTM A902 provides standardized definitions for terms related to metallic-coated steel products, ensuring clarity and consistency in technical communication. ASTM B750 is referenced for the chemical composition requirements of the GALFAN alloy used for the