1.Will minor scratches cause rust?
The structure of color-coated panels is "substrate + primer + topcoat". If the scratch only breaks the surface topcoat or primer and does not expose the internal substrate, the substrate is still under coating protection, isolated from air and moisture, and will not rust in a short period of time.
Although the substrate is not exposed, the damaged coating may become a "breakthrough" for water vapor and pollutants to penetrate. If it is exposed to humidity, high salt fog or industrial dust for a long time, the coating may gradually peel off from the scratches, indirectly causing corrosion of the substrate. Therefore, it is recommended to apply special repair paint to the scratches in time to seal the damaged area.
2.Will deep scratches cause rust?
If the scratch is deep and directly exposes the internal substrate, it depends on the type of substrate:
The substrate is a galvanized sheet (mainstream): The galvanized layer itself has a sacrificial anode protection effect. If the scratch only exposes the galvanized layer without damaging the underlying steel plate, the zinc layer will slowly oxidize to form a passivation film. In the short term, only slight white rust may appear instead of red rust. However, if the galvanized layer is thin, or in a high humidity and high salt environment, the zinc layer will be consumed faster, eventually causing the underlying steel plate to rust.
The substrate is an ordinary cold-rolled steel plate:
If the substrate has no galvanized layer, the scratch will expose the steel plate and it will be directly exposed to air and moisture. Red rust may appear in a short period of time, and the rust will spread along the scratch to the surrounding area, destroying the adhesion of the coating.
3.What are the key factors affecting rust speed?
Environmental humidity: In rainy and humid areas, water vapor condenses quickly at the scratches, and the rust rate is 3-5 times faster than in dry areas.
Corrosive media: If it is located in coastal areas, industrial areas or around chemical plants, the corrosive components in the air will accelerate the oxidation of the substrate. Even a slight scratch that exposes the bottom may show obvious rust within 1-2 months.
Timely treatment of scratches: If the scratches are not repaired in time after they are found, the rust will "spread" from the damaged area - on the one hand, the rust will penetrate along the gap between the coating and the substrate, causing the coating to bubble and peel off; on the other hand, the expansion of the rust volume will further expand the scope of the scratch, forming a vicious cycle.
4.How to avoid rust caused by scratches?
Reduce scratches during installation: Avoid friction with hard objects during transportation and installation, use special tools to reduce burrs during cutting, and clean up metal debris on the surface after installation.
Repair scratches in time: After finding scratches, use sandpaper to lightly grind the damaged area to remove floating rust and impurities, and then apply repair paint of the same color as the color-coated plate to form a closed protective layer. 3. Choose high-quality substrates: Galvanized substrates (zinc layer thickness ≥ 120g/m²) or aluminum-zinc alloy substrates are preferred. Their corrosion resistance is far better than that of ordinary cold-rolled steel plates. Even if slight scratches occur, the anti-rust period is longer.
5.In summary, will scratches cause rust?
Minor scratches: No rust in the short term, but need to be repaired in time to prevent the coating from peeling off. Deep scratches: Galvanized substrates may delay rusting, while ordinary steel plates will rust quickly, and the more humid and corrosive the environment, the faster it will rust.