Prepainted Galvalume Coil, also called Ppgl Coil or Ppgl Steel Coil, is an important material for building curtain walls, appliance housings, and cold – chain transportation. Its corrosion resistance affects the product’s service life, maintenance cost, and safety. In tough environments like marine areas and industrial pollution zones, finding ways to boost the corrosion resistance of Ppgl Steel is a big concern in the industry. This article gives five useful strategies based on real – world use.
I. Make the Substrate Better: A Good Start for Corrosion Resistance
The corrosion resistance of Ppgl Steel depends on its substrate, the aluminized zinc – plated substrate (Galvalume Coil).
1. Control the Coating: Good Ppgl Steel Coil needs the right mix of aluminum (55%), zinc (43.4%), and silicon (1.6%). Silicon helps form an alloy layer and stops the zinc layer from peeling. The aluminized zinc coating should be at least 120 g/m² (both sides). In very corrosive coastal areas, it can be over 150 g/m² to form a strong protective layer.
2. Choose a Clean Substrate: The Ppgl Steel substrate should have low levels of impurities like carbon and sulfur. This reduces small defects and stops corrosion from starting. It’s better to use aluminized zinc – plated substrates that meet ASTM A792 standards to lower the risk of corrosion.
II. Pretreat the Surface Well: Improve Coating Adhesion
The adhesion of the Prepainted Galvalume Steel Coil affects its corrosion resistance. Surface pretreatment is very important:
1. Clean in Three Steps: The substrate should go through alkaline washing to remove oil, acid washing to remove rust, and rinsing to neutralize. This makes sure the surface is clean and stops “intercalation corrosion” between the coating and the substrate.
2. Upgrade Passivation: Use chromate passivation or chromium – free passivation (which is better for the environment). This forms a uniform passivation film on the Galvalume Steel Coil substrate. It helps the coating stick better and blocks corrosive substances.
3. Dry Properly: After pretreatment, dry the substrate quickly. Keep the surface moisture below 0.1% to prevent pitting corrosion.

III. Pick the Right Coating: Build a Multi – layer Protection
The coating is the main protection for Coil Ppgl. When choosing a coating system, think about weather resistance, chemical resistance, and adhesion:
1. Choose the Primer: Epoxy primers are good because they stick well and block corrosive substances. For high – requirement cases, use polyurethane primers to make the coating more flexible and resistant to salt spray.
2. Choose the Topcoat: Pick weather – resistant coatings.
– For normal environments: High – weather – resistant polyester topcoats are a good choice. They resist UV and aging well and are not too expensive.
– For tough environments (like marine or industrial areas): PVDF (polyvinylidene fluoride) topcoats are best. They are very resistant to weather and chemicals and can last over 20 years.
3. Control the Coating Thickness: The primer should be 5 – 7μm thick, the topcoat 15 – 20μm. The total coating thickness should be at least 25μm to avoid problems like pinholes.
IV. Follow Good Production and Installation: Avoid Corrosion from Mistakes
Even high – quality Prepainted Galvalume Coil can lose its corrosion resistance if it’s processed wrongly:
1. Control the Coating Process: Use roller coating to make the coating even. Keep the curing temperature at 230 – 250℃ for 30 – 60 seconds. This prevents the coating from getting too brittle.
2. Protect During Installation:
– Don’t scratch the PPGL Coil surface. Fix scratches with special repair paint right away.
– Leave expansion joints when installing to stop the coating from cracking due to temperature changes.
– In coastal or humid areas, use stainless steel fasteners to avoid corrosion from different metals touching.
V. Maintain Regularly: Make the Coil Last Longer
Regular maintenance can slow down corrosion, especially for outdoor Galvalume Steel Coil:
1. Clean Often: Clean the coil with water or a neutral detergent at least 1 – 2 times a year. This removes dust, salt, and other dirt that can cause corrosion.
2. Fix Damage Fast: If there are any scratches or damage to the coating, use matching repair paint right away to stop corrosive substances from reaching the substrate.
3. Isolate from the Environment: For coils near acid or alkali sources or by the sea, use protective barriers or coatings to reduce contact with corrosive substances.