1.How to assess the depth of a scratch?
Minor scratches: Only the topcoat layer is damaged; the primer layer remains intact. There is no noticeable unevenness when touched, and the metal substrate is not exposed.
Moderate scratches: The scratch has penetrated both the topcoat and primer layers, exposing the metal substrate. This is the most common and requires the most repair, as the corrosion protection barrier has been compromised.
Severe scratches: The scratches are very deep, not only exposing the metal but also causing noticeable dents or damage to the metal substrate.
2.How to repair minor scratches (damaging only the topcoat)?
Cleaning: Use a clean, soft cloth dampened with alcohol or diluted neutral detergent to carefully wipe the scratched area to remove oil and dust.
Polishing: Use a fine-grit automotive polishing wax or abrasive compound to gently polish the scratch in circular motions with a soft cloth. By removing a small amount of the surrounding paint layer, the scratch can be made less noticeable.
Glazing (Optional): After polishing, you can apply a layer of automotive wax to protect the polished area and add shine.
3.How to repair moderate scratches (exposed metal, the most common and must be repaired)?
Surface Cleaning: Thoroughly clean the scratch and surrounding area with a non-woven cloth dampened with alcohol, ensuring no grease, dust, or moisture remains. This is the first step in ensuring adhesion.
Surface Treatment (Light Sanding): Gently sand the inside and edges of the exposed metal scratch using fine sandpaper. The purpose is to remove any burrs and rust, and to increase surface roughness, improving paint adhesion. Clean again with alcohol after sanding.
Apply Primer (Optional but Recommended): If the scratch area is large or in a highly corrosive environment, it is recommended to apply a coat of clear passivating solution or a dedicated anti-rust primer, which provides additional corrosion protection.
Apply Repair Paint:
Using a soft-bristled brush or toothpick, apply a small amount of repair paint.
Apply thin, multiple coats to the scratch, ensuring the paint completely covers the exposed metal.
After the first coat dries (usually a few minutes to half an hour according to the paint instructions), apply a second coat. Repeat 2-3 times until the paint is slightly higher than the surrounding intact coating.
Surface Leveling: After applying the final coat, while it is still slightly damp, lightly brush the edges to create a smoother transition between the touch-up paint and the existing coating.
Curing: Allow it to cure naturally in a well-ventilated area for 24-48 hours. Avoid touching, getting it wet, or exposing it to direct sunlight during this time.
4.How to repair severe scratches (with substrate dents)?
Shaping: If the board shape allows, gently tap the dent from the back using a rubber mallet, wooden block, or similar tool to smooth it out as much as possible. Note: Be gentle to avoid further damage to the coating.
Corrosion Prevention and Filling:
Clean and sand according to the steps in Solution Two.
Fill the dent with rust-resistant putty. After smoothing, allow it to harden completely.
Smooth the dried putty surface with fine sandpaper.
Painting: Apply repair paint to the smoothed putty surface according to the steps in Solution Two.
5.What are some things to keep in mind when performing repairs?
Color Difference Issues: No matter how hard you try, the repaired color will rarely perfectly match the original coating. The color and gloss of the new paint may differ from the original coating after aging and exposure to light. This is acceptable in situations where appearance requirements are extremely high (such as the exterior of building facades).
Repair Locations:
Outdoor/Moisture-Contact Sides: Repairs must be strictly followed to ensure proper corrosion protection.
Indoor/Dry Environments: Requirements can be relaxed somewhat, but exposed metal parts must still undergo corrosion protection treatment.
Large Area Damage: If the scratches cover a large area, it is recommended to replace the entire panel, as repairs may be costly and ineffective.
Prevention is Key: Taking appropriate protective measures during transportation, handling, processing, and installation (such as using protective pads and avoiding dragging) is the most economical and effective way to prevent scratches.