1.How does coating type and composition affect mechanical scratch resistance?
Fluorocarbon coating:
With fluorocarbon resin as the main component, it has a stable molecular structure and low surface tension, high hardness and excellent wear resistance. It is not easy to leave marks under slight friction, and local scratches may appear under strong scratches, but the coating is not easy to fall off as a whole. The scratch resistance is top-notch among all kinds of coatings.
Polyester coating (PE):
It is divided into ordinary polyester and high weather-resistant polyester, with a pencil hardness of about 1H-2H and medium wear resistance. It can withstand daily slight scratches (such as friction with gloves during installation), but sharp objects (such as screwdrivers and gravel) are prone to obvious scratches when scratched, and if the force is strong, it may damage the substrate.
Silicon-modified polyester coating (SMP):
The hardness is slightly higher than that of ordinary polyester (pencil hardness 2H), and the wear resistance is close to that of fluorocarbon coating, but the flexibility is slightly worse. It is stable under medium-intensity abrasions (such as slight collisions with metal parts), and the coating may break when severely abraded.
Other coatings:
Such as acrylic coating (pencil hardness ≤ 1H), epoxy coating (high hardness but high brittleness), have weak abrasion resistance, and even a slight scratch may cause the coating to break.
2.How do coating thickness and adhesion strength affect mechanical abrasion resistance?
Coating Thickness:
The greater the total dry film thickness, the thicker the "buffer layer" against scratches. For example, an 80μm-thick fluorocarbon coating will produce 30%-40% less damage than a 50μm-thick coating of the same type under the same scratching force. However, excessive thickness may increase the coating's brittleness and make it more susceptible to peeling.
Adhesion Strength:
The stronger the adhesion between the coating and the substrate, the less likely it is to completely peel off when scratched. For example, a coating with an adhesion strength of 7N/cm may only leave a shallow mark after a scratch, while a coating with an adhesion strength of less than 3N/cm may cause "flaking" due to scratching.
3.How do substrate pretreatment and coating processes affect mechanical scratch resistance?
Substrate surface treatment:
The substrate needs to be pre-treated by phosphating, passivation, etc. to form a rough and stable surface to enhance the bonding strength with the coating. Poor pre-treatment will lead to weak adhesion of the coating, which is easy to peel off from the interface when scratched.
Coating process:
Roller coating (good uniformity) is more resistant to scratches than spray coating; the molecular cross-linking of the coating that is fully baked and cured is more compact, and the hardness and wear resistance are better than the coating that is not sufficiently cured.
4.How does scratch resistance perform in actual applications?
Daily light contact: Most coatings (PE and above) can withstand it without noticeable damage.
Routine handling during installation (such as gentle handling of tools and minor collisions with brackets): Fluorocarbon and SMP coatings perform reliably, while PE coatings may leave shallow marks without compromising protective properties. Rough handling (such as dragging or heavy impacts with metal objects) may cause noticeable scratches on all coatings.
Natural abrasions in long-term outdoor environments (such as wind and sand erosion and bird strikes): Fluorocarbon coatings, due to their excellent wear resistance, will only show minor gloss loss and no noticeable scratches within 5-10 years. Ordinary PE coatings may experience localized gloss loss or shallow marks after 3-5 years due to wind and sand abrasion.
Severe accidental abrasions (such as vehicle collisions and impacts with falling objects): Regardless of the coating type, coating damage may occur, exposing the substrate. Prompt repair (such as application of touch-up paint) is required to prevent rust.
5.What are the measures to improve mechanical scratch resistance?
Choose a high-hardness coating: Fluorocarbon (PVDF) or high-weather-resistant polyester coating is preferred to ensure that the pencil hardness is ≥2H.
Increase coating thickness: Increase the dry film thickness to 80-120μm (primer 20-30μm + topcoat 60-90μm) to enhance buffering capacity.
Apply a wear-resistant layer on the surface: Some high-end products will apply a layer of transparent wear-resistant resin (such as polysiloxane) on the surface of the topcoat to further enhance scratch resistance.
Optimize substrate pretreatment: Use chromium-free passivation or nano-ceramic pretreatment to enhance the adhesion of the coating to the substrate and reduce coating peeling when scratched.