What Happens If Embedded Rebar Is Not Anti-Rust Treated After Welding? Corrosion Hazards and Rectification Solutions

When the embedded steel bars of GRC curtain walls are welded without anti-rust treatment, they are prone to rusting in the natural environment, triggering a series of chain problems that seriously threaten the structural safety of the curtain wall. Clarifying the hazards of rust and taking timely corrective measures is key to preventing safety risks from escalating. Drawing on actual maintenance cases, Qinglong analyzes the core consequences and solutions.

1. Steel Bar Rusting and Decay: Reduced Load-Bearing Capacity

After welding, the surface oxide layer of embedded steel bars is destroyed. Without anti-rust treatment, they are easily corroded by oxygen and moisture, producing rust. Rust volume is 2-4 times that of the steel bar itself, reducing the cross-sectional area of the bar and gradually weakening its strength. Welded areas, due to material changes, corrode even faster; in severe cases, the cross-sectional loss rate of the steel bar can exceed 30%, greatly reducing load-bearing capacity. In an old building renovation project, Qinglong found that embedded steel bars without anti-rust treatment showed severe rust at the welded areas after 5 years of use, with tensile strength dropping by 40%—no longer meeting design load requirements and requiring urgent reinforcement.

2. Rust Expansion and Cracking: Damage to Surrounding Structures

The expansion force generated by rusting steel bars squeezes the surrounding GRC components and the concrete main structure, causing cracking and damage. GRC components, due to their relatively lower strength, are prone to radial cracks around embedded steel bars; crack width grows with the degree of rust, and in severe cases leads to component detachment. Affected by the expansion force, the concrete main structure develops surface spalling and cracks, undermining its structural integrity. During maintenance of a residential project, Qinglong found that GRC components around untreated embedded steel bars had cracks up to 0.5mm wide, with concrete surface spalling exceeding 0.1㎡, requiring removal of the damaged components and re-construction.

3. Connection Joint Failure: Compromised Curtain Wall Stability

Embedded steel bars are the core of the connection between GRC components and the main structure. Rusting can cause connection joint failure and create safety risks. Rust at welded areas reduces weld strength and can even cause weld fracture, leading to loosening and displacement of GRC components. The bond between steel bars and concrete weakens due to rust, preventing effective load transfer; in extreme cases, components may fall. During an inspection of a commercial project, Qinglong found gaps at the bond interface between untreated embedded steel bars and concrete, with slight displacement already occurring in the components—requiring immediate reinforcement measures.

4. Emergency Rectification and Preventive Measures: Preventing Hazard Escalation

For embedded steel bars without anti-rust treatment, timely rectification and a preventive mechanism are required. Treatment of rusted steel bars: for slight rust, use mechanical derusting + anti-rust paint coating + sealant sealing; for severe rust, removal and replacement are required, with anti-rust treatment applied according to standards after re-welding. Preventive measures: derust immediately after welding the embedded steel bars, apply two coats of anti-rust paint, and additionally wrap the welded areas with anti-corrosion tape; seal the joints after installation and incorporate them into routine inspections, checking the rust condition every 6 months. Through standardized anti-rust treatment and maintenance, Qinglong effectively avoids rust hazards of embedded steel bars, ensuring the long-term safety of GRC curtain walls.