Dome Cap Nut

Dome Cap Nut — Acorn / Cap Nut | DIN 1587 | Decorative & Protective Dome-Top Design

Dome cap nuts, also known as acorn nuts, feature a closed dome-shaped top that covers and protects the exposed threads of bolts and threaded rods. Manufactured to DIN 1587 and DIN 917 standards, our dome cap nuts are available in M4 to M24 sizes in carbon steel, 304/316 stainless steel, and brass. The dome design not only provides a clean, professional appearance but also prevents thread damage, contamination, and moisture ingress — making them ideal for architectural, automotive, and decorative applications where both aesthetics and protection matter.

Material & Specifications

Size Range	M4 to M24 / 5/16″ to 1″
Standard	DIN 1587 (high dome), DIN 917 (low dome), ANSI B18.2.2, ISO 4035
Material	Carbon Steel (Grade 5, 8), 304 Stainless Steel (A2), 316 Stainless Steel (A4), Brass (CuZn)
Surface / Coating	Electroplated Zinc (Blue/White, Yellow/Color), Hot-Dip Galvanized, Dacromet, Multi-Element Alloy Co-Permeation, Polished (SS), Chrome Plated
Dome Height	Standard dome (DIN 1587) or Low dome (DIN 917)
Thread Type	Metric Coarse (M), UNC, UNF

Surface Treatment & Zinc Coating Quality

The dome cap nut’s visible top makes surface finish quality especially important. We offer premium coating options that combine corrosion protection with aesthetic appeal:

• Hot-Dip Galvanizing (HDG) — Thick zinc layer (50-120μm) providing superior long-term corrosion protection for outdoor and marine environments. Compliant with ISO 1461 / ASTM A153. Ideal for infrastructure and coastal applications requiring maximum durability.
• Electroplated Zinc Blue-White (Zn Blue/White) — Bright, clean silver-blue appearance with 5-15μm zinc layer. Cr3+ trivalent passivation, RoHS compliant. The preferred finish for visible decorative applications requiring an attractive, uniform appearance.
• Color Zinc / Yellow Zinc (Iridescent Passivation) — Golden-iridescent multi-colored passivation offering 150-200 hours salt spray resistance. Provides both corrosion protection and a distinctive visual finish for automotive and equipment applications.
• Dacromet Coating — Water-based zinc-chromium flake coating with NO hydrogen embrittlement risk. 1,000+ hours salt spray resistance. Silver-gray metallic finish. Ideal for automotive engine compartments, underbody, and industrial environments with chemical exposure.
• Multi-Element Alloy Co-Permeation — Zinc-aluminum-rare earth alloy layer offering 2-3x corrosion resistance of traditional galvanizing. Self-healing at scratches. Used in premium architectural and marine applications where long-term appearance retention is critical.

Key Features

• Closed dome top protects exposed bolt threads from damage, dirt, and moisture
• Smooth, rounded surface provides a safe, snag-free finish ideal for public areas
• Available in polished stainless steel for premium architectural applications
• Internal thread ensures full engagement with bolt for secure fastening
• Multiple dome heights (standard and low profile) to suit clearance requirements

Applications

• Architectural metalwork and decorative fittings
• Automotive trim and exterior exposed fasteners
• Furniture and playground equipment
• Food processing and pharmaceutical equipment (stainless steel)
• Marine and coastal installations requiring thread protection

Why Choose BoltNutsPlus?

• ISO 9001:2015 Certified Manufacturing — consistent quality you can trust
• 15+ Years of Export Experience — serving 40+ countries worldwide
• Full Traceability — material certificates (EN 10204 3.1) and test reports included
• Custom Packaging & OEM/ODM — your brand, your specifications
• Third-Party SGS / Bureau Veritas Inspection Available
• 24-Hour Quote Response — same-day reply for urgent requirements