RUSPERT Self-Tapping Screws–A Technical Overview of Anti-Corrosion Self-Tapping Fasteners

2026-07-13

Self-tapping screws with RUSPERT surface treatment combine the convenience of thread-forming installation with a premium three-layer anti-corrosion coating system. This document provides a concise overview of self-tapping screw types and the RUSPERT coating technology that delivers 1,000+ hours of salt spray protection without hydrogen embrittlement risk.

Part 1 — Self-Tapping Screw Types

Self-tapping screws form their own internal threads during installation, eliminating the need for pre-tapping operations. Four primary categories serve different materials and load requirements, each distinguished by its thread-forming mechanism and point geometry.

Type Classification

Type	Standard	Description	Best For
Thread-Forming	Type A / AB / B	Displaces material to form internal threads. Requires a pilot hole. No material removal.	Plastics, soft metals, wood
Thread-Cutting	Type F / BF / 25	Features cutting flutes that remove material during installation, creating clean threads.	Harder metals, brittle materials
Thread-Rolling	Type TR / LO-DRIVE	Cold-forms threads without cutting. Produces no chips. Higher loosening resistance.	Sheet metal, extruded holes
Self-Drilling	DIN 7504 / TEK	Integral drill-bit point drills and taps in one operation. No pilot hole required.	Thin-gauge steel, HVAC, roofing

Key Characteristics

Thread-Forming (Type A/AB/B): Displaces material to form threads. Requires a pilot hole. Best for plastics and soft metals where material can flow without fracturing.

Thread-Cutting (Type F/BF/25): Features cutting flutes that physically remove material, creating clean, precise threads. Ideal for harder metals and brittle materials that cannot be displaced.

Thread-Rolling (Type TR/LO-DRIVE): Cold-forms threads without cutting, producing no chips. Offers higher resistance to vibration loosening due to work-hardened thread flanks.

Self-Drilling (DIN 7504/TEK): Integral drill-bit point enables drilling and tapping in a single operation. No pilot hole needed for thin-gauge steel sheet, significantly reducing assembly time.

Common Standards & Materials

Standards: DIN 7976, DIN 7504, ISO 15480, GB/T 43655

Materials: Carbon steel (C1018–C1045), alloy steel, stainless steel

Head types: Pan head, countersunk (flat head), hex head, hex washer head, round head

Part 2 — RUSPERT Coating Technology

RUSPERT (路锈宝) is a high-grade, environmentally friendly surface treatment system commonly applied to carbon and alloy steel fasteners. It utilises a three-layer coating structure that combines sacrificial galvanic protection with a durable ceramic barrier, achieving 1,000–1,500 hours of neutral salt spray resistance — far exceeding conventional zinc plating.

Three-Layer Structure

Layer	Composition	Function	Protection Mechanism
Layer 1 — Metallic Zinc	Electrodeposited zinc	Sacrificial cathodic protection for steel substrate	Galvanic — zinc corrodes preferentially
Layer 2 — Chemical Conversion	Chromate / passivation film	Promotes adhesion between zinc and ceramic layers	Chemical bonding + self-healing
Layer 3 — Baked Ceramic Topcoat	Zinc-aluminum flake + resin	Barrier against moisture, salt, oxygen and chemicals	Physical barrier + non-conductive

The three layers are bonded together through chemical reactions, forming a dense, rigid film that adheres tightly to the steel substrate. This unique combination of layers provides both active (sacrificial) and passive (barrier) corrosion protection.

Key Advantages

Superior corrosion resistance: 1,000–1,500 hours neutral salt spray (NSS) per ISO 9227, compared to 96–240 hours for standard zinc plating.

No hydrogen embrittlement: Low-temperature curing process avoids hydrogen absorption, making RUSPERT safe for high-strength fasteners (Grade 8.8–12.9) where electroplating poses embrittlement risk.

Higher surface hardness: RUSPERT coating is harder than Dacromet, providing superior wear and scratch resistance during installation and service.

Prevents bimetallic corrosion: The non-conductive ceramic topcoat isolates the zinc layer from contact with dissimilar metals (e.g., aluminum, galvanized steel), eliminating galvanic corrosion of adjacent structures.

Environmentally compliant: Cr⁶⁺-free, RoHS and REACH compliant. No toxic hexavalent chromium used in the process.

Coating Comparison

Property	RUSPERT	Zinc Plating	Dacromet
Salt Spray (hrs)	1,000 – 1,500	96 – 240	500 – 1,200
Hydrogen Embrittlement	None	Risk (Grade 10.9+)	None
Surface Hardness	High	Medium	Medium
Cr⁶⁺ Free	Yes	Varies	Yes
Appearance	Dark grey / black	Blue-white / clear	Silver-grey
Bimetallic Corrosion	Prevented	Possible	Reduced
Cost Level	Medium-High	Low	Medium

Salt spray per ISO 9227 NSS. Bimetallic corrosion refers to galvanic attack when RUSPERT-coated fasteners contact aluminum or galvanized steel surfaces.

Applications

Coastal & marine: Roofing, cladding, and structural connections in salt-laden atmospheres.

Outdoor structures: Fencing, decking, pergolas, and architectural facades exposed to weather.

ACQ-treated timber: RUSPERT withstands the corrosive copper-based preservatives in modern pressure-treated wood.

Automotive: Underbody fasteners, chassis connections, and exhaust system attachments.

Wind energy & steel framing: Long-life structural connections requiring maintenance-free corrosion protection.

Summary

RUSPERT-coated self-tapping screws offer a compelling combination of installation convenience and long-term corrosion protection. The self-tapping design eliminates pre-tapping, while the three-layer RUSPERT system delivers 1,000+ hours of salt spray resistance without hydrogen embrittlement — making these fasteners ideal for outdoor, coastal, and chemically aggressive environments where conventional zinc plating would fail prematurely.

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