ISO 3506-6:2020

Overview

ISO 3506-6:2020 - "Fasteners - Mechanical properties of corrosion‑resistant stainless steel fasteners - Part 6" provides general rules and technical guidance for selecting stainless steels and nickel alloys suitable for the manufacture and use of corrosion‑resistant fasteners. It is intended to be used together with the other parts of the ISO 3506 series (e.g., Parts 1, 2 and 5) and includes informative Annex A with common designations of steels and nickel alloys used for fasteners.

Key topics and technical requirements

• Material groups and grades: Describes austenitic (A1–A5, A8), martensitic (C1, C3, C4), ferritic (F1) and duplex/austenitic‑ferritic (D2, D4, D6, D8) stainless steel families used for fasteners.
• Chemical composition guidance: Provides rules and references for chemical composition specifications that affect corrosion resistance and mechanical behaviour (to be used with Parts 1/2).
• Corrosion mechanisms and resistance:
  • Stress corrosion cracking (SCC) - identifies susceptibility factors and guidance for selection to reduce SCC risk.
  • Pitting and crevice corrosion - explains selection criteria, especially for chloride‑containing environments.
  • Intergranular corrosion - notes the role of carbon content and stabilization (e.g., L grades or Ti/Nb‑stabilized steels).
  • Intermetallic phase formation - highlights susceptibility issues at elevated temperatures.
• Temperature suitability: Typical service temperature ranges by group (examples given in the standard: austenitic down to −196 °C up to +300 °C; martensitic −40 °C to +230 °C; ferritic −20 °C to +250 °C; duplex −40 °C to +280 °C).
• Magnetic permeability: Discusses magnetic properties and effects of cold work on residual magnetism.
• Practical selection advice: Notes surface condition, galvanic compatibility, and that the overall assembly corrosion resistance is governed by the lowest grade present. Recommends consulting fastener manufacturers or metallurgists for special cases.

Practical applications - who uses this standard

• Fastener manufacturers specifying suitable stainless steel fasteners and nickel alloy fasteners.
• Design and mechanical engineers selecting materials for bolted joints in corrosive or high‑temperature environments.
• Procurement and quality inspectors verifying material selection and conformity with ISO 3506 series.
• Metallurgists and corrosion engineers advising on material choice for marine, chemical, pool or high‑temperature service.

Typical use cases: bolts, screws, studs, nuts, tapping screws and special high‑temperature fasteners where corrosion resistance, mechanical performance and environmental compatibility are critical.

Related standards

• ISO 3506‑1 - Bolts, screws and studs (grades and property classes)
• ISO 3506‑2 - Nuts (grades and property classes)
• ISO 3506‑5 - Special fasteners and nickel alloys for high temperature applications

Keywords: ISO 3506-6:2020, stainless steel fasteners, corrosion‑resistant, nickel alloys, austenitic, martensitic, ferritic, duplex, pitting, crevice corrosion, stress corrosion cracking, material selection.