How to Handle Rust Stain Seepage on Exterior Wall GRC?

When rust stains seep out onto the surface of exterior wall GRC, it is usually caused by corrosion of internal metal components (such as ordinary steel reinforcement, embedded parts, or installation anchors), with rust water penetrating to the surface through the capillary pores of the GRC. This not only affects aesthetics, but also signals a potential safety hazard in the internal connection system, requiring immediate investigation of the cause and systematic treatment. Based on years of maintenance experience, Qinglong Group has summarized a four-step treatment method: "survey and diagnosis, eradicating the rust source, surface repair, and long-term protection."

The first step in treating rust stains is precise survey and cause diagnosis. The source of the rust must be identified: is it the steel mesh inside the GRC panel that lacks sufficient rust resistance? Is it embedded parts that are not made of stainless steel or not adequately treated for corrosion protection? Or was the waterproofing layer damaged during later installation, allowing moisture to intrude and corrode the metal anchors? Sometimes an endoscope or localized destructive inspection is needed to locate the corrosion points. At the same time, the severity of the corrosion must be assessed to determine whether it has already affected the structural safety of the component.

Eradicating the rust source is the key to treatment, and targeted measures must be taken according to the cause of corrosion. If the corrosion originates from the reinforcement bars inside the panel and covers a large area, the most reliable solution is to replace the GRC component. If the corrosion is limited to local embedded parts or anchors, localized chiseling can be performed to expose the corroded metal; after thorough rust removal, apply a high-performance anti-rust paint such as epoxy zinc-rich primer, and then restore the area using polymer repair mortar. All treatments must ensure that the rust source is completely isolated.

Surface repair and long-term protection are the guarantees for restoring aesthetics and preventing recurrence. Existing rust stains can be cleaned with a specialized rust stain remover. After the repair is completed, apply a high-quality penetrating water repellent or silane protective agent to the GRC surface to form a protective film that prevents external moisture from intruding again. Meanwhile, check the joint sealing of the entire curtain wall system to ensure it remains intact. For major corrosion problems, Qinglong recommends commissioning a professional institution to conduct a safety assessment and establishing a regular inspection system to prevent problems before they occur.