How to Treat Rust Stain Seepage on Exterior Wall GRC? — Qinglong Group's Full-Process Rust Corrosion Treatment Solution

Rust exudation on GRC exterior walls is a serious problem affecting both aesthetics and safety, requiring prompt scientific treatment. Based on 28 years of maintenance experience, Qinglong Group has developed a four-step treatment solution—inspection and assessment, surface treatment, anti-rust repair, and protective reinforcement—to effectively resolve corrosion problems and extend service life.

Corrosion inspection and assessment is the foundation of treatment. A rebar locator is used to determine the corrosion location, and phenolphthalein solution tests the carbonation depth. In its maintenance projects, Qinglong Group measures rebar potential with a potentiometer; when the potential is below -350mV (relative to a Cu/CuSO₄ electrode), active corrosion is identified. Infrared thermal imaging can detect internal hollowing, while the tapping method checks for bond loss. A targeted plan is formulated after a comprehensive assessment to avoid overtreatment.

Surface treatment is the critical step. For minor rust stains (affected area <10%), mechanical grinding is applied until a solid substrate is exposed, with grinding depth not exceeding 1/3 of the cover thickness. Qinglong Group uses a specialized rust remover (phosphoric acid-based, pH=2-3) to neutralize residual iron ions, followed by rinsing with a high-pressure water jet (pressure ≤150Bar) until neutral. Severely corroded areas require chiseling away loose concrete, with the edges cut at an angle to enlarge the repair contact surface.

Anti-rust repair requires professional materials. Qinglong Group applies a migrating corrosion inhibitor (amino alcohol-based) to the rebar surface to form a protective film. Polymer-modified cement-based materials are selected for the repair mortar, with shrinkage <0.02% and bond strength >2.0MPa. After repair, the surface undergoes profile matching to ensure consistency with the original finish. In coastal area projects, sacrificial anode protection is added to repaired areas, providing long-term rust protection.

Protective reinforcement prevents recurrence. The surface is coated with a silane impregnation agent (penetration depth ≥3mm), achieving a contact angle above 100°. A regular inspection regime ensures early detection and prompt treatment, preventing minor issues from developing into major defects. Through systematic treatment, GRC exterior walls can be restored to their original condition, with service life extended by more than 10 years.