CSA C49.2-10 (R2018): Zinc-Coated Steel Wire Strand for Guy, Messenger, and Span Wire Applications – Technical Overview

Introduction

CSA C49.2-10 (R2018) is a Canadian national standard developed by the Canadian Standards Association (CSA) that specifies requirements for zinc-coated (galvanized) steel wire strand used primarily as guy, messenger, and span wires in overhead utility line construction. The standard was originally published in 2010 and reaffirmed without technical change in 2018, hence the designation R2018. It provides manufacturers, utilities, and contractors with a unified set of performance criteria to ensure the mechanical integrity and corrosion resistance of steel strand products installed across Canada and in international markets where CSA standards are referenced.

Scope and Field of Application

CSA C49.2-10 covers stranded steel wires made from high-strength carbon steel, with a hot-dip zinc coating applied after stranding. The strand is intended for static non–cyclic loading applications such as:

• Guy wires – diagonal tension members that support utility poles and towers.
• Messenger wires – horizontal catenary supports for self-supporting aerial cables.
• Span wires – tensioned wires used to suspend traffic signals, street lights, or other overhead equipment.

The standard applies to strands with diameters ranging from 6.4 mm (1/4 in.) up to 22.2 mm (7/8 in.), in both Class A and Class B coating weights. It does not cover strand for prestressed concrete, suspension bridge cables, or electrical conductors, which are addressed by separate CSA or ASTM standards.

Technical Requirements

Materials and Manufacturing

The steel wire base shall be made from high-quality carbon steel produced by the open-hearth, basic-oxygen, or electric-furnace process. The zinc coating is applied by the hot-dip method after the individual wires have been drawn to final size. All wires must be free of surface defects and butt welds, except that welds are permitted in the finished strand provided they do not reduce the breaking strength below the specified minimum.

Tensile Properties

The strand must meet the minimum breaking force values listed in Table 1. Strength classes are based on nominal strand diameter and number of wires (common constructions are 3-wire, 7-wire, and 19-wire).

Breaking strength tests must be performed on full-length strand samples in a calibrated tensile testing machine. The elongation at break shall not be less than 4 % for strand sizes up to 12.7 mm and not less than 3 % for larger sizes.

Zinc Coating and Adhesion

Coating uniformity is verified by a minimum weight per unit area as shown in Table 1, using a gravimetric stripping method (hydrochloric acid with antimony trioxide). Additionally, adhesion is checked by wrapping the zinc-coated wire around a mandrel of specified diameter (typically 3 times the wire diameter) at a rate of one turn per second; the coating must not flake or crack to the extent that bare steel is exposed.

Dimensions and Tolerances

The strand diameter is measured at any cross section. The tolerance is ±2 % for diameters 9.5 mm and above, and ±2.5 % for smaller sizes. The lay length (pitch) of the outer wires must be between 10 and 16 times the nominal strand diameter for 7-wire constructions, with adjustments for other wire counts.

Implementation Highlights

• Sampling and Testing: One sample from each production lot (maximum 50 t) is tested for breaking strength, coating weight, and adhesion. If any test fails, two additional samples from the same lot are tested; if either fails, the lot is rejected.
• Marking: Each reel or coil must be tagged with the manufacturer’s name, standard designation (CSA C49.2-10), strand size, class of coating, length, and lot number.
• Packaging: Strands must be wound on reels or in coils such that they are free of kinks and damage during transit. The inside diameter of coils must not cause the strand to bend below a radius equal to 24 times the strand diameter.
• Third-Party Certification: While not mandatory, many utilities require that the strand be certified by a CSA‑accredited laboratory to confirm conformity with the standard.

Compliance and Quality Assurance

Manufacturers seeking to comply with CSA C49.2-10 should establish a quality management system in line with ISO 9001 or equivalent. Key quality control points include:

• Verification of steel wire rod chemistry and mechanical properties prior to drawing.
• Continuous monitoring of zinc bath temperature and composition during hot-dip galvanizing.
• In-line tension control during stranding to ensure uniform lay and minimize internal stress.
• Final inspection of strand diameter, surface finish, and bend characteristics.

The standard itself does not require third-party certification, but most Canadian electrical utilities and telecom operators mandate compliance as a condition of procurement. Audits may be performed by the utility or an independent agency to verify production records, test results, and traceability.

Frequently Asked Questions

Year of last review: 2026. The information provided in this article is for educational purposes and does not substitute for the official CSR C49.2-10 (R2018) publication. Always consult the latest version of the standard for detailed requirements.