What Are the Consequences of Skipping Anti-Rust Treatment After Welding Embedded Rebar? Hazard Analysis and Qinglong Group's Zero-Tolerance Standard

If embedded steel bars (or steel plates) within GRC components are not treated for rust prevention after welding, a chain of catastrophic consequences will follow: accelerated electrochemical corrosion in the weld zone, rust expansion stress cracking the GRC protective layer, reduced load-bearing capacity endangering safety, and high repair costs. Accelerated corrosion tests at Qinglong Group's laboratory show that welded points without anti-rust treatment corrode at a rate 5-10 times faster than unwelded areas in humid environments, and can cause cracks along the steel bars in the surrounding GRC within 3-5 years. During the repair of an early project in Shenzhen, we chiseled open a cracked GRC column cladding and found that the weld seams of the internal embedded parts had corroded into a honeycomb structure, with the surrounding concrete loose, leaving us no choice but to carry out extensive reinforcement. Welding destroys the passivation film or galvanized layer on the metal surface, creating the most active corrosion anode—post-treatment is essential.

Electrochemical Corrosion Principles Make It High-Risk

The high temperature during welding burns off the galvanized layer or passivation film on the steel bar surface and alters the metal microstructure of the weld seam and heat-affected zone, making the electrode potential more negative and turning it into the anode of the corrosion cell, so that it corrodes preferentially and at an accelerated rate. The corrosion products expand 2-6 times in volume, exerting enormous circumferential tensile stress on the surrounding GRC.

Escalating Consequences: From Visual Damage to Structural Failure

Initially, rust stains appear at the weld seams; then rust expansion forces cause slender cracks in the GRC protective layer (usually only 15-25mm thick); the cracks accelerate the intrusion of moisture and oxygen, forming a vicious cycle of “corrosion–cracking–worse corrosion,” ultimately leading to embedded part failure and component detachment. This is particularly dangerous for cantilevered components.

Qinglong Group's Standard “Welding–Anti-Rust” Process

We strictly prohibit welding at GRC installation sites. All embedded parts requiring welding must be completed in the factory. Immediately after welding, they undergo “slag chipping – grinding – cleaning – brushing with zinc-rich anti-rust paint (dry film thickness ≥80μm)” treatment, and may only proceed to the next process after passing inspection. This is our quality red line, with zero tolerance.

Embedded parts are the “roots” of GRC, and the weld zone is a “wound in the root.” Qinglong Group applies the most rigorous processes to eliminate future problems and ensure connections remain secure for a hundred years.