Flat Washer

Flat Washer — Standard Flat Round Washer | DIN 125 / ISO 7089 | Carbon & Stainless Steel

Flat washers are the most fundamental and widely used washer type in industrial fastening. Manufactured to DIN 125, ISO 7089, and ANSI B18.22.1 standards, our flat washers are designed to distribute the load of a threaded fastener, prevent surface damage to the mating material, and provide a smooth bearing surface. Available in sizes from M3 to M48 in carbon steel, 304/316 stainless steel, and alloy steel, our flat washers serve as the essential load-bearing component in virtually every bolted assembly across all industries.

Material & Specifications

Size Range	M3 to M48 / 1/8″ to 2″ (Larger sizes available upon request)
Standard	DIN 125 (Type A/B), ISO 7089, ISO 7090, ANSI B18.22.1, GB/T 97.1, GB/T 97.2
Material	Carbon Steel (Grade 4.8, 8.8, 10.9 compatible), 304 Stainless Steel (A2), 316 Stainless Steel (A4), Brass, Aluminum, Nylon/Plastic
Surface / Coating	Hot-Dip Galvanized (HDG), Electroplated Zinc Blue/White, Color Zinc/Yellow, Dacromet, Multi-Element Alloy Co-Permeation, Plain/Black Oxide, PTFE Coated
Hardness	100-300 HV (varies by material and standard grade)
Types	Type A (standard OD), Type B (large OD), Extra Thick/Heavy Series, Fender Washers (extra-large OD)

Surface Treatment & Zinc Coating Quality

At BoltNutsPlus, we understand that surface treatment is critical to fastener longevity and performance. Our washers undergo rigorous coating processes to ensure maximum corrosion resistance and durability. We offer five premium coating options, each tested to international standards:

• Hot-Dip Galvanizing (HDG) — Thick zinc layer (50-120μm) providing superior long-term corrosion protection for outdoor, marine, and industrial environments. Compliant with ISO 1461 / ASTM A153 standards. Salt spray resistance: 500-1,000+ hours. HDG washers are ideal for structural steel assemblies exposed to harsh weather.
• Electroplated Zinc Blue-White (Zn Blue/White) — Bright, clean silver-blue appearance with 5-15μm zinc layer. Cr3+ passivation technology, fully RoHS compliant. Ideal for indoor machinery, electronics, and general-purpose applications requiring aesthetic appeal and moderate corrosion resistance.
• Color Zinc / Yellow Zinc (Iridescent Passivation) — Multi-colored iridescent passivation film offering enhanced corrosion resistance (100-200 hours salt spray) with a distinctive golden finish. Widely preferred in automotive, agricultural equipment, and construction machinery sectors for its balanced protection and visual appeal.
• Dacromet Coating — Advanced water-based zinc-chromium coating technology with NO hydrogen embrittlement risk. Provides 1,000+ hours salt spray resistance, making it the preferred choice for high-strength fasteners in extreme environments. Environmentally friendly (no heavy metal discharge), RoHS/ELV compliant, ideal for automotive and wind energy applications.
• Multi-Element Alloy Co-Permeation — Zinc-aluminum-rare earth alloy layer offering 2-3x the corrosion resistance of traditional galvanizing. Features self-healing properties at scratch points, ensuring long-term protection even in damaged areas. Ideal for critical infrastructure, power transmission towers, coastal projects, and marine installations.

Key Features

• Uniform load distribution prevents damage to mating surfaces and reduces embedding in soft materials
• Smooth, flat bearing surface ensures consistent bolt preload and prevents galling during tightening
• Available in multiple outer diameter series (standard, large, extra-large) for different load requirements
• Precision stamping with clean, burr-free edges ensures consistent dimensions and trouble-free assembly
• Surface treatments tested to ISO 9227 neutral salt spray standards for verifiable corrosion performance
• Full traceability with heat/lot numbers enabling material certs (EN 10204 3.1) for critical applications

Applications

• General construction and structural steel connections — most common washer type
• Machinery assembly, equipment mounting, and vibration-prone installations
• Automotive chassis, engine, and suspension system fastening
• Electrical panel mounting and busbar connections (with insulating flat washers)
• HVAC, plumbing, and piping system flange connections
• Agricultural machinery and heavy equipment assembly

Why Choose BoltNutsPlus?

• ISO 9001:2015 Certified Manufacturing — consistent quality you can trust on every batch
• 15+ Years of Export Experience — serving 40+ countries across 6 continents
• Full Traceability — material certificates (EN 10204 3.1) and comprehensive test reports included
• Custom Packaging & OEM/ODM — your brand identity, your specifications, our precision manufacturing
• Third-Party SGS / Bureau Veritas Inspection Available upon request
• 24-Hour Quote Response — same-day reply for urgent requirements; standard 24-hour turnaround