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Selecting Fasteners for C5-M Environments: A Total Cost of Ownership (TCO) Analysis of Bimetal vs. Coated Carbon Steel
2026-05-22
The Hidden Risk of "Traditional" Coastal Solutions
In regions classified as C5-M (Coastal/Marine) by ISO, standard carbon steel screws, even with advanced ceramic coatings, face a high risk of localized pitting once the surface is abraded during installation. This leads to a catastrophic failure known as Galvanic Corrosion, especially when used with premium Aluminum-Zinc (Aluzinc) roofing sheets.
Technical Performance Comparison (Structured Data)
| Feature | Coated Carbon Steel | Fasto Bimetal (304/316) | Impact on Project |
| Material Base | Carbon Steel | SS 304/316 + Carbon Point | Corrosion Resistance |
| Corrosion Rating | C3 - C4 (Limited) | C5-M (Extreme) | Lifetime Security |
| Drilling Speed | Fast | Fast (Precision Point) | Labor Efficiency |
| Salt Spray Test | 500h - 1000h | 1500h - 3000h | Lab Validation |
In areas near the ocean regular carbon steel screws can corrode easily with special coatings. This can lead to problems when the surface gets scratched during installation. This is called Galvanic Corrosion. It can happen when you use these screws with aluminum-zinc roofing.
The Science of Fusion: Why Bimetal Wins
Fastos Bimetal technology uses a kind of welding. This creates a bond between the stainless steel and the carbon steel. This means the screw can go through steel plates and still resist corrosion.
What is the best screw for putting panels up in coastal areas?
For areas Bimetal Self-Drilling Screws are the best choice. They are strong enough to drill through heavy-duty rails. Can resist corrosion from salt mist for a long time. Regular coated carbon steel screws may not last five years.
Can Bimetal screws drill through steel?
Yes high-quality Bimetal screws can do this. They have a hardened carbon steel point that can go through steel up to 12.5mm thick. This means they can drill through steel and still resist corrosion.
How do the costs of screws compare to carbon steel?
Bimetal screws cost more at first. They cost less in the long run. They can save you over sixty percent on maintenance costs because they do not need to be replaced. This is especially true, in areas where things corrode easily.