1.How should we understand the electrical conductivity of color-coated steel rolls?
Metal substrate (galvanized steel sheet, aluminum sheet, etc.): Excellent conductor.
Chemical conversion layer (passivation layer): Extremely thin, with little impact on overall conductivity.
Organic coating (primer + topcoat, such as polyester, fluorocarbon, etc.): Insulator.
2.What is the effect of coating oxidation on the electrical properties of the coating itself?
Organic coatings (polymers) are inherently good insulators with extremely high resistivity.
Oxidative aging primarily leads to polymer chain breakage and destruction of cross-linked structures, potentially producing small polar molecules. Theoretically, this could transform the coating from an "excellent insulator" to a "still very good insulator," but such an absolute change in resistivity (e.g., from 10¹⁵ Ω·cm to 10¹³ Ω·cm) is generally negligible in practical engineering applications because its insulating properties remain far superior to those of metals.
3.What are the key effects of coating oxidation on the overall structural conductivity?
Powdering, cracking, and peeling: The final stage of coating oxidative aging involves powdering (the surface resin degrades into powder) and microcracks. This leads to:
Reduced or partially lost insulation layer thickness: Electrons can more easily penetrate the coating through tunneling or direct contact.
Exposed conductive substrate: If cracks penetrate deeply or the coating peels off, the conductive metal substrate is directly exposed, and that point becomes a good conductor.
Decreased hygroscopicity and adhesion: Aging coatings become more hygroscopic. Moisture (a weak electrolyte) seeps into cracks or the interior of the coating, forming a localized, unstable conductive channel, significantly reducing surface resistance.
4.What are the risks associated with coating oxidation when used as building materials (roofing, wall panels)?
The risk is low. However, if severe pulverization and peeling occur, the exposed substrate may affect electromagnetic shielding or grounding continuity.
5.What are the risks of coating oxidation when used as an electrical appliance casing/housing?
High risk. If the coating ages and cracks, its insulation performance will decline, potentially increasing the risk of the casing becoming electrified and jeopardizing safety.