November 2025: New Standard for Stainless Steel Flat Washers Released

In November 2025, professionals in the field of mechanical systems and components for general use see a significant milestone: the publication of EN ISO 3506-7:2025, a new international standard that details the mechanical properties and required grades for corrosion-resistant stainless steel flat washers. Aimed at ensuring higher reliability and interoperability in fastened joints, this update impacts manufacturers, quality managers, engineers, and procurement specialists worldwide.

This article provides an in-depth look at the new standard, key requirements, and its impact on industry compliance and best practices.

Overview of the Mechanical Systems Components Sector

The mechanical systems and components for general use category covers the essential elements that underpin countless industries—from infrastructure to automotive, machinery, and industrial equipment. In this sector, reliable fasteners (bolts, screws, washers, nuts) are foundational to safety, durability, and performance. Standards like those in the EN ISO 3506 series define the properties and usage of corrosion-resistant stainless steel parts, supporting quality assurance and global trade.

Why do standards matter here? Because only through uniform, internationally recognized specifications can manufacturers guarantee compatibility, safety, and lifecycle cost savings in assemblies. For engineers and purchasing teams, up-to-date standards mean greater confidence and fewer failures—boosting competitiveness and compliance.

This article explores:

• What the latest EN ISO 3506-7:2025 standard means for flat washers
• Who should comply and why
• Key technical requirements and practical implementation tips
• How your business can benefit

Detailed Standards Coverage

EN ISO 3506-7:2025 – Stainless Steel Flat Washers: Grades and Property Classes

Fasteners – Mechanical properties of corrosion-resistant stainless steel fasteners – Part 7: Flat washers with specified grades and property classes (ISO 3506-7:2024)

The newly published EN ISO 3506-7:2025 delivers a comprehensive framework for flat washers made from corrosion-resistant stainless steel. These washers are crucial in bolted joints, where they distribute load, reduce wear, and ensure tight, corrosion-resistant connections—particularly when paired with bolts, screws, studs, and nuts as specified in EN ISO 3506-1 and EN ISO 3506-2.

Scope and Application

The standard applies to a broad range of flat washers:

• Plain washers (with or without knurls, ribs, or chamfers)
• Square washers and square hole washers
• Shaped plates (flat, captive, and non-captive washers)
• Thickness range from 0.2 mm to 6 mm

It specifies both the mechanical and physical properties required for washers made from austenitic, ferritic, and duplex stainless steel grades. The designation system helps users choose the correct material and property class, ensuring both compatibility and optimal performance in mechanical assemblies. The new standard fills a previous gap by consolidating requirements for stainless steel washers, making market expectations clearer for users, distributors, and manufacturers.

Key Requirements and Specifications

• Material Types: Classifies washers by stainless steel group—austenitic, ferritic, and duplex—with detailed references to property classes and designated grades.
• Mechanical & Physical Properties: Sets out minimum hardness, strength, ductility, and corrosion resistance appropriate for the chosen stainless steel type.
• Temperature Range: Washers are tested at ambient temperatures (10°C to 35°C) and are intended for service from –20°C to +150°C. However, specific applications may expand from –196°C to +300°C, subject to user risk assessment.
• Designation System: Introduces a coding system for specifying grade and property class—facilitating correct selection and interoperability with bolts, screws, studs, and nuts.
• Inspection & Testing: Details procedures and requirements for manufacturers, suppliers, and purchasers, including hardness testing (Vickers method), surface finish inspection, and reporting protocols.
• Marking & Labelling: Washers and packaging must be clearly marked with grade and property class for traceability and quality control.

Target Users and Compliance Obligations

• Manufacturers: Responsible for meeting material, process, and testing guidelines.
• Distributors and Stockists: Need to ensure compliance in their supply chains.
• Industries/Projects: Construction, automotive, heavy machinery, energy infrastructure, and anywhere robust, corrosion-resistant fasteners are used.

Practical Implications and Changes from Previous Practices

• Provides a unified set of property classes across the entire EN ISO 3506 series, reducing uncertainty and increasing safety in design and procurement.
• Makes global sourcing easier—conforming to this standard signals high reliability to buyers and regulatory bodies.
• Captures new advances in steel grades and property class combinations, reflecting the latest manufacturing and metallurgical knowledge.

Key highlights:

• Applies to washers for all major fastener types (bolts, screws, studs, self-threading screws)
• Uniform requirements for mechanical and physical properties now across all washer types/forms
• Clear marking, traceability, and quality management guidelines

Access the full standard:View EN ISO 3506-7:2025 on iTeh Standards

Industry Impact & Compliance

Adoption of EN ISO 3506-7:2025 introduces new compliance checkpoints and performance guarantees for manufacturers and end-users:

• Enhanced Quality Assurance: Aligning purchasing and manufacturing with this standard can significantly minimize the risk of corrosion-related failures in bolted assemblies.
• Regulatory Compliance: As the standard is adopted in national regulations and project specifications, non-compliant washers may not be accepted on major infrastructure or industrial projects.
• Streamlined Procurement: With property class and grade codification, purchasing departments can specify requirements confidently, reducing delays or errors due to miscommunication.
• Risk Management: Reduced liability for assembly failures, especially in demanding environments (marine, chemical process, construction, automotive), by using verified, marked components.

Compliance Timeline

• Immediate: New projects should reference EN ISO 3506-7:2025 for design and purchase.
• May 2026: Conflicting national standards to be withdrawn; full transition required for European and international projects.

Risks of Non-compliance

• Project rejection,
• Increased maintenance costs due to premature corrosion or failure,
• Liability in case of accidents or regulatory audits.

Technical Insights

Common Requirements Across The EN ISO 3506 Series

• Chemical composition limits for each steel grade ensure consistent corrosion resistance.
• Vickers hardness test methods are prescribed for verification of mechanical performance.
• Packaging and marking promote traceability, which is vital during audits or investigations.

Implementation Best Practices

1. Material Selection: Match washer material and property class with intended bolt/screw material and environmental exposure. Use the property class system to reduce galvanic corrosion risk in assemblies.
2. Inspection & Testing: Establish clear protocols for in-house and third-party testing—especially for hardness and surface condition.
3. Documentation and Traceability: Maintain documentation (batch certificates, inspection reports) for all washers to facilitate compliance audits.
4. Supplier Quality Management: Work with suppliers who demonstrate conformity, using the updated marking system for quick checks.

Testing and Certification Considerations

• Third-party certification strengthens customer trust and simplifies contract negotiation.
• Internal quality audits should be based on the hardness, chemical, and dimensional requirements outlined in the new standard.

Conclusion & Next Steps

The release of EN ISO 3506-7:2025 provides long-awaited clarity and harmonization for stainless steel flat washers in bolted joints. By adopting this standard, organizations ensure higher reliability, streamlined supplier communications, and full regulatory compliance in mechanical assemblies.

Key takeaways:

• The new standard applies to all major types of flat washers made of stainless steel and formalizes mechanical and physical property requirements.
• Adopting EN ISO 3506-7:2025 reduces technical and legal risks in critical assemblies.
• Early adoption is recommended as conflicting national standards will be withdrawn by May 2026.

Recommendations:

• Update your project specifications and procurement documents to reference EN ISO 3506-7:2025.
• Audit current stock and supply chains to ensure compliance by the transition deadline.
• Stay informed about new or revised standards in mechanical systems and components via authoritative sources like iTeh Standards.

Ready for the next step?Access the full EN ISO 3506-7:2025 document on iTeh Standards

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