1.What is Galvanized Coil Z275?
Z: stands for hot-dip pure zinc (Galvanized).
275: stands for the total weight of the double-sided coating of 275 grams per square meter (g/m²). This is a medium-thick zinc coating specification that can provide good basic anti-corrosion protection, but its life is still limited when used alone in extreme environments such as severe pollution and seaside.
2.Why do we need to perform "two coatings and two bakings" on Z275 galvanized coils?
Enhanced protection: To significantly improve its corrosion resistance, weather resistance and aesthetics in harsh environments (such as high pollution, high salt fog, strong ultraviolet rays).
Provide color and function: Give steel a variety of colors, glossiness and additional functionality (such as self-cleaning, antibacterial, high weather resistance, etc.).
Extend service life: The composite coating system formed by "two coatings and two bakings" can provide protection far beyond the bare galvanized layer.
3.What is the "two coatings and two bakings" process?
First coat (primer coating): Apply a layer of primer to the pre-treated galvanized surface.
Primer function: Key adhesion: Provide the strongest bonding with the galvanized substrate.
Basic corrosion protection: Enhance the overall corrosion protection (especially the protection of cuts and edges).
Isolation barrier: Prevent the metal ions of the substrate from migrating upward to affect the topcoat.
Cathodic protection: Some primers (such as epoxy primers) contain corrosion-inhibiting pigments (such as strontium chromate, etc., and now more environmentally friendly chromium-free alternatives are used) to provide additional cathodic protection.
First baking (primer curing): ◦ Pass the primed steel plate through a high-temperature baking oven (usually at a temperature of about 200°C - 250°C).
The purpose is to allow the resin in the primer to undergo a cross-linking reaction, completely cure, and form a tough, dense paint film.
Second coat (topcoat coating): Apply the topcoat on the cured primer layer.
Topcoat function: Ultimate protection: Provides the outermost layer of weather resistance (resistance to UV rays, rain, temperature differences, and pollutant erosion).
Beautiful decoration: Provides a variety of colors, glossiness (high gloss, matte, matte, etc.) and texture effects.
Special functions: Can have self-cleaning, anti-scratch, antibacterial, heat insulation and cooling functions (depending on the topcoat formula).
Second baking (topcoat curing): The steel plate with topcoat is passed through a high-temperature baking oven again (the temperature is usually similar to or slightly lower than the baking primer). The topcoat is completely cured to form the final protective and decorative layer.
4.What are the advantages of the "two-coat, two-bake" process?
Better overall performance: Primer and topcoat each have their own functions and clear division of labor, and together they build a more complete protection system. Primer ensures adhesion and basic anti-corrosion, and topcoat provides optimal weather resistance and beauty.
Stronger corrosion resistance: The double-layer barrier significantly extends the service life of steel plates in harsh environments, especially at scratches or cuts, where primers can provide additional protection.
Better weather resistance and color and gloss retention: High-quality topcoats (such as PVDF fluorocarbon topcoat, HDP high weather-resistant polyester) can effectively resist UV degradation, chalking and fading, and maintain long-term beauty. Wider application adaptability: It can meet the needs of more demanding buildings (such as high-end factories, airports, stadiums), home appliances, harsh industrial environments, etc.
5.How does the "two-coat and two-bake" color-coated plate of Z275 substrate perform when used in a highly corrosive environment?
Galvanized layer (Z275): Sacrificial anode protection (especially for cuts and scratches).
Primer layer: Enhanced adhesion, basic anti-corrosion, sealing effect.
Topcoat layer: Excellent weather resistance, decorative, additional barrier protection.
This composite structure makes its performance far superior to bare galvanized coil (Z275) in environments with severe pollution, strong ultraviolet rays, industrial areas, and seaside, and is also better than single-layer coated color-coated plates.