Don’t Seal the Steel: Why Vent Holes Matter in Galvanizing

gokul raj
19 minutes ago
2 min read

What are Vent Holes?

Vent holes are openings strategically placed in hollow or tubular steel structures to allow air, moisture, and gases to escape during the galvanizing process. When steel is dipped into molten zinc (at temperatures around 450°C / 840°F), any trapped air or moisture inside sealed sections can expand rapidly — potentially causing explosions or deformation.

Why Vent Holes Matter

1. Safety First

During galvanizing, sealed air inside unvented steel sections can lead to dangerous pressure build-up. This can cause parts to rupture or even violently explode in the zinc bath — posing serious safety risks to personnel and damaging equipment.

2. Complete Zinc Coverage

Without proper venting and draining, zinc cannot flow freely inside hollow sections. This results in uneven coatings, unprotected areas, and ultimately, premature corrosion. Well-placed vent holes ensure the zinc reaches every internal surface for full protection.

3. Smooth Processing

Efficient venting and draining reduce the time steel parts spend in the zinc bath and simplify handling. It also prevents zinc from pooling inside the structure, which can add unnecessary weight and waste material.

4. Compliance with Standards

Standards like ASTM A385, ISO 1461, and Australian Standard AS/NZS 2312.2 outline clear safe galvanizing, consistent zinc coverage, and long-term corrosion requirements for vent and drain hole placement, size, and design. Following these guidelines ensures protection. Compliance not only enhances quality but also meets regulatory expectations in both local and international markets.

Design Tips for Effective Venting

Hole Placement: Always place vent holes at the highest point and drain holes at the lowest point of the structure when oriented for dipping.
Hole Size: As a rule of thumb, holes should be at least 1/2 inch (13 mm) in diameter, or as specified in galvanizing standards based on the section size.
Aesthetic Considerations: Vent holes can often be placed in hidden or less visible areas, or incorporated into weld seams, to maintain the appearance of architectural elements.

What we deliver at Sharcon?

Galvanizing vent holes and chamfers provided as per AS/NZS 2312.2 for all steel sections.
Custom vent and drain hole placement designed for safety, coating efficiency, and structural integrity.
Precision fabrication ensuring proper hole sizing and location based on steel geometry.
Consultation with galvanizers to meet project-specific requirements and optimize coating quality.
High standards of workmanship that align with Australian and international galvanizing codes.
Experience with all steel member types, including RHS, SHS, CHS, beams, channels, and fabricated assemblies.