How to Treat Rust Stain Seepage on Exterior Wall GRC? Qinglong GRC Rust Stain Treatment Technical Guide

Treatment of rust stain bleed-out on GRC exterior walls must follow the four-step method of "source identification, rust removal, rust inhibition, and protection". First, identify the rust source (rebar corrosion or metal fitting corrosion), then thoroughly remove it using mechanical grinding (rust removal grade Sa2.5) plus chemical rust removal (phosphoric acid concentration 15%-20%), then apply rust inhibitor (calcium nitrite type, dosage 3%), and finally carry out surface repair and protective treatment. After treatment, bond strength ≥1.0MPa, expected protection life ≥10 years.

Specific treatment process: when corrosion depth is ≤1mm, grinding is applied; when >1mm, chiseling out and repair is required. In one project, GRC moldings showed rust stain bleed-out; inspection revealed insufficient cover thickness (only 8mm) and a rebar corrosion rate of 7%. After treatment, bond strength reached 1.2MPa, with no recurrence over 3 years of use. The Qinglong GRC anti-rust treatment system achieves a treatment success rate of over 95%.

Rust Source Diagnosis Techniques

Use a rebar locator to detect cover thickness, and the half-cell potential method to detect corrosion activity. Where necessary, drill and take cores to directly observe the corrosion condition. Establish corrosion severity grading standards to guide the formulation of treatment plans.

Rust Removal Process Standards

Mechanically remove rust until the original metal color is exposed, with surface cleanliness at Sa2.5 grade. Control the pH of the chemical rust removal solution between 1-3, with a treatment time of 5-10 minutes. After rust removal, surface chloride content ≤0.05%.

Rust Inhibition Treatment Requirements

Migrating corrosion inhibitor dosage 200-300g/㎡, penetration depth ≥20mm. Film-forming corrosion inhibitor thickness ≥50μm, continuous with no missed application. The corrosion inhibitor has good compatibility with subsequent coatings.

Protection and Repair Measures

Repair material compressive strength ≥40MPa, bond strength ≥1.5MPa. Protective coating alkali resistance ≥300h, salt spray resistance ≥1000h. Flatness deviation between the repaired area and the substrate ≤1mm.

Rust stain treatment requires addressing both symptoms and root causes. The Qinglong GRC system solution thoroughly resolves corrosion problems.