For self-drilling screws used in roofing, curtain walls, solar structures, and infrastructure, material selection and surface protection are no longer optional—they are central to longevity, safety, and life-cycle cost.
Recently, innovation has accelerated around stainless steel grades, bimetallic cores, and advanced passivation or coating systems. The winning fastener must drill, cut threads, and resist decades of weather. Here’s a deep dive into the pros and cons, trending technologies, and what specifiers should demand in 2025.
Pros: inherent corrosion resistance + compatibility
Because corrosion resistance in stainless is intrinsic (not just a surface film), stainless screws can maintain performance even if scratched.
Common austenitic grades such as 304 (“18-8”) and 316 offer excellent general resistance to atmospheric corrosion and many aggressive environments; 316 is preferred in chloride or marine conditions.
Stainless fasteners avoid galvanic mismatch when fastening to stainless or aluminum substrates (if properly insulated).
Maintenance overhead is lower: less need for repainting or sacrificial coatings over time.
Many stainless grades (304, 316) are relatively soft compared to hard carbon or alloy steel, making them less suited for drilling thick/hardened substrates without strain or tip wear.
Hardened 410 stainless can deliver better drill-through performance, but at the cost of reduced corrosion resistance relative to 304/316.
Stainless raw material and processing cost are higher than plain carbon or zinc-coated steel, so cost sensitivity in budget projects remains a barrier.
Over-torque, galling, or improper installation (excessive speed/heat) can degrade performance or cause failure, especially in soft or thin sections.
Use 410 or heat-treated stainless for aggressive drilling tasks (thicker steel), but accept tradeoffs in corrosion performance.
For pure exposure resistance, 316 stainless is often the minimum for marine or chloride-laden settings.
Consider duplex or super-duplex stainless steels (e.g. SAF 2205, SAF 2507, Zeron 100) in extreme chemical or offshore environments—they combine higher strength and chloride resistance.
Pre-passivation can help build a more stable, protective oxide barrier and reduce chloride ingress in the critical early life of the fastener.
Bimetallic screws combine a corrosion-resistant outer shell (often stainless) with a high-strength inner core (often carbon or alloy steel). The outer “skin” guards against rust and environment, while the inner core provides hardness and drilling capacity.
Some manufacturers use a hardened drill tip (e.g. tool steel) fused or bonded to a stainless-body screw, effectively giving a drilling “head” that can handle hard substrates while preserving the stainless body.
Balanced performance: better drill-through ability than pure stainless, yet superior corrosion resistance vs ordinary carbon fasteners.
Extended service life: in many structural or façade projects, bimetal screws are spec’d to reduce maintenance cycles.
Wider applicability: can be used in mixed-material assemblies, harsher climates, or when drilling thicker metals.
Cost-effective lever: some bimetal solutions hit a “sweet spot” of cost vs longevity that pure stainless or exotic alloys can’t match.
The interface (bond) between core and shell is a potential weak point—if the bond fails (cracks, delamination), the protective shell may be compromised.
Manufacturing quality control is essential: poor bonding, voids, or mismatched expansion can lead to corrosion or failure.
The outer layer must maintain continuity (no breaches, scratches) to preserve corrosion protection.
In extreme corrosive conditions, even the outer shell must be high-grade stainless or special alloy to avoid pitting or crevice attack.
The global market for bimetallic barrel and screw products is projected to grow with a CAGR of ~8.5% in the coming decade, reflecting strong industrial demand.
Many engineering publications highlight how bimetal screws are gaining traction in infrastructure, energy (wind, solar), and façade work.
