Why Bimetal Screws Are Now the Go-To for Solar and Heavy Steel

The Problem with “Stainless” in Tough Steel

Stainless steel screws (A2 / A4) are chosen primarily for corrosion resistance, and in that role, they perform well. The issue appears when they are expected to drill through thick, high-strength steel.

Common on-site problems include:

• Slow drilling speed in dense steel

• Excessive heat buildup at the drill point

• Snapped screws under impact driver torque

• Seized fasteners that stop installation progress

On a large solar installation, a handful of broken or seized screws doesn’t just waste material—it interrupts workflow and idles the entire crew. Corrosion resistance has no value if the screw never seats correctly.

The Bimetal Fix: A Division of Labor

A bimetal screw addresses these problems by assigning each task to the material best suited for it.

• The Tip – Hardened Carbon Steel
  Functions as a true cutting tool, penetrating thick steel quickly and cleanly with minimal heat generation.

• The Body – Stainless Steel
  Provides corrosion resistance for the exposed portion of the fastener after installation.

By separating drilling performance from long-term corrosion resistance, bimetal screws reduce installation failures while maintaining durability over decades of service.

Will the Buried Tip Rust? (The Practical Answer)

A common concern is whether the carbon steel tip, once embedded, will corrode from the inside. In practice, this is rarely an issue.

Corrosion requires oxygen and moisture. Once installed, the drill point is locked inside the substrate and isolated from both. Real-world failures in solar and roofing systems almost always originate at exposed areas—around the head, washer, or sealing interface. These are precisely the areas protected by the stainless steel portion of a bimetal screw.

Why Solar Contractors Are Leading the Shift

Solar projects amplify every fastener weakness. Three factors are driving bimetal screws toward default status:

• Unforgiving Substrates
  Steel thickness and hardness often exceed initial plans. Reliable drilling is non-negotiable.

• High Access Costs
  Replacing a failed screw on a rooftop array means equipment mobilization and lost power generation.

• 25-Year Design Life
  Solar warranties assume minimal maintenance. Installation errors at the fastener level are unacceptable.

In this context, installation reliability matters as much as corrosion resistance.

The Real Cost Isn’t on the Invoice

While bimetal screws have a higher unit price than standard stainless screws, project economics are driven by installed cost, not piece cost.

Key contributors include:

• Labor efficiency: Faster drilling increases output per installer

• Material waste: Fewer snapped screws and stripped heads

• Tool longevity: Reduced wear on drill bits and drivers

• Callbacks: Fewer returns to address leaks or loose connections

When these factors are accounted for, the “cheaper” fastener often becomes the more expensive choice over the life of the project.

When to Stick with Standard Stainless

Bimetal screws are not universal. Standard stainless steel screws remain appropriate for:

• Thin-gauge or pre-drilled metal

• Low-volume installations where speed is not critical

• Decorative or architectural applications where appearance is prioritized

The key is matching fastener performance to real installation conditions, not defaulting based on material alone.

Conclusion

The rise of bimetal screws is not a trend—it’s a correction. It reflects how modern solar and steel construction actually works, under time pressure, with harder materials and long service-life expectations.

For applications where installation failure and future access costs are unacceptable, bimetal screws have become the logical, cost-effective standard. They are designed not just to resist corrosion, but to install reliably on day one and stay forgotten for decades.

We supply high-quality, customizable fasteners to meet a wide range of project needs.

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