In structural welding, the job isn’t finished when the last bead is laid. The “finish” of a weld and the surrounding steel determine two critical factors: how long the structure will last (corrosion resistance) and how it will look (architectural aesthetics).
At Weld Rich & Steel, we apply specific finishing standards to ensure that every project—from industrial beams to custom staircases—stands up to Ontario’s environment.
1. Why Finishing Matters
Without proper finishing, even the strongest weld is vulnerable. In the Greater Toronto Area, road salt, high humidity, and extreme temperature swings can cause rapid oxidation (rust). Proper finishing:
- Prevents structural weakening due to corrosion.
- Prepares the surface for long-lasting paint or powder coating.
- Removes sharp edges and spatter for safety and aesthetics.
2. Common Welding Finishes and Treatments
Depending on the project requirements, we utilize several levels of finishing:
Cleaning and Slag Removal
Every weld pass, especially in SMAW or FCAW, leaves behind slag.
The Process: We use chipping hammers and wire wheels to clean the weld to its base metal. This is not just for looks—it is required for a proper visual inspection of the weld’s integrity.
Grinding and Sanding (Architectural Finish)
For “AESS” (Architecturally Exposed Structural Steel), such as indoor mezzanines or handrails, the weld needs to be invisible or smooth.
The Process: We grind the weld flush with the base metal and sand it to a specific grit. This creates a seamless look once the metal is painted.
Spatter Removal
Welding often creates “spatter” (small beads of molten metal).
The Process: We use anti-spatter sprays during welding and mechanical scrapers afterward to ensure a clean surface. Spatter must be removed because it can pop off later, taking the paint with it and leaving a hole for rust to start.
3. Protective Coatings
The final step in finishing is the protective barrier. The three most common choices in Ontario are:
- Shop Primer: A temporary coating that protects the steel during transport and erection. Ideal for steel that will be enclosed inside a building.
- Hot-Dip Galvanizing: The gold standard for outdoor structures. The steel is dipped in molten zinc, creating a metallurgical bond that can last 50+ years.
- Powder Coating: Offers a durable, high-quality colored finish. Best for architectural elements where branding or design is key.
4. Maintenance and Longevity
A good finish reduces maintenance costs. We recommend regular visual inspections of outdoor steelwork to catch “nicks” in the coating before rust can spread beneath the surface.
FAQ: Welding Finishes
Do all welds need to be ground flush?
No. In most industrial structural applications, grinding a weld flush can actually weaken it if not done correctly. We only grind welds flush when specifically requested for architectural reasons (AESS).
What is the best finish for outdoor steel in Toronto?
Hot-dip galvanizing is the most effective defence against Ontario’s winter salt and moisture.
Can you paint over a fresh weld immediately?
No. The weld must be cooled, cleaned of all slag/flux, and often degreased. Painting over a dirty weld will lead to the paint peeling within months.