What Bimetal Actually Does

A bimetal screw is exactly what it sounds like: two metals in one fastener.

• The body is stainless steel (A2 or A4). That’s for corrosion resistance where you can see it.

• The tip is hardened carbon steel. That’s for drilling through thick steel without burning up.

Stainless alone is great against rust but soft when drilling. Carbon steel drills like a dream but needs coatings to survive outside. Bimetal just lets each material do what it’s good at. The tip cuts. The body resists. Simple concept, harder to manufacture well.

Where Coated Steel Starts to Struggle

Let’s be clear: coated steel isn’t going away. It still makes sense for plenty of jobs. But the limits are real.

Coatings get scratched

Every time a screw drives through metal, something rubs. If that rub scratches through the zinc, the exposed steel starts rusting. You might not see it for years, but it’s happening.

Outdoor exposure adds up

Twenty years of sun, rain, and temperature swings will test any coating. In coastal areas, salt speeds everything up. What looked fine at year five can be failing at year ten.

Replacement is expensive

A failed screw on a ground-level fence? No big deal. A failed screw on a rooftop solar array? Now you need lifts, labor, and downtime. The screw cost nothing. The replacement costs thousands.

That math changes how people spec fasteners.

How Bimetal Answers Those Problems

Bimetal doesn’t rely on a coating that can scratch off. The stainless body is corrosion-resistant all the way through. The carbon tip is buried in the steel, isolated from air and moisture, so it doesn’t become a rust path.

Drilling performance stays consistent because the tip is actually hard. No overheating, no galling, no snapped screws halfway through a run. Installers notice the difference faster than engineers do.

Where You See Bimetal Most NowSolar mounting systems

Twenty-five year warranties don’t leave room for fastener experiments. Bimetal gives the corrosion resistance of stainless with the drilling power crews need for thick steel purlins.

Metal roofing

Commercial roofs are expensive to access. Fasteners that last as long as the panels themselves are worth the upgrade.

Coastal and industrial construction

If there’s salt or chemicals in the air, coated steel is a gamble. Stainless bodies remove that gamble.

What Fasto Does Here

Fasto manufactures bimetal self-drilling screws for these exact applications. Stainless bodies, hardened tips, production controlled to DIN and ISO. Testing verifies drilling capacity, strength, and corrosion performance. Batch traceability means if something does go wrong, you can track it back.

For projects where failure isn’t an option, that level of control matters more than the price per piece.

Bottom Line

Coated steel isn’t dead. It’ll keep showing up on job sites for years. But the trend is clear: as projects get tougher and lifetimes get longer, bimetal keeps gaining ground. It solves the trade-off that coated steel can’t—drilling performance without compromising corrosion resistance.

For buyers planning installations meant to last decades, the question isn’t really “should we consider bimetal?” anymore. It’s “why wouldn’t we?”

Media Contact
Company Name: FASTO
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Country: China
Website: https://www.fastoscrews.com/