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Concept Guide

Fastener Materials

Carbon steel, alloy steel, stainless A2 and A4, and heat-resistant grades — how the service environment drives the material choice, and which coatings this library pairs with it.

The selection order

Material choice follows the environment; the strength class and the coating follow the material.

  1. Environment first — indoor, outdoor, humid, marine, or elevated temperature. This decides the material family before anything else.
  2. Material family — carbon steel, alloy steel, stainless steel, or a heat-resistant grade.
  3. Property class — the strength the joint needs, which must exist for that material and size. See /mechanical-properties/.
  4. Coating — selected after the material and the strength class, because some coatings and high-strength classes interact. See /surface-treatment/.

Materials recorded in this library

Every material family in this library is a row in the standards data source.

Material familyGrades recorded against itNotes
Carbon steel4.6, 5.6, 5.8, 8.8, Grade 5, Grade 8General engineering, indoor and sheltered outdoor use with a coating.
Alloy steel10.9, 12.9Higher property classes; typically paired with a coating that does not embrittle.
Stainless steel (A2)A2-70Austenitic 304 family. Corrosion resistance without a coating.
Stainless steel (A4)A4-70, A4-80Austenitic 316 family, including the higher-strength A4-80 condition.
Heat-resistant martensitic steel40Cr10Si2MoElevated-temperature service. See 40Cr10Si2Mo.
The grades listed in each row are the ones actually recorded for that material in this library's data source. No additional material capability is claimed.

Stainless steel: A2 and A4

Two stainless families are recorded in this library.

GradeFamilyWhere it is used in this library
A2-70304-type austeniticRecorded across the metric bolt, nut and washer standards
A4-70316-type austeniticRecorded across the metric bolt, nut and washer standards
A4-80316-type austenitic, higher strengthRecorded for DIN 912 and ISO 4762
A4 has the higher alloy content of the two families, which is why it is the usual choice where chloride exposure matters. Strength values for each grade are on the linked property pages.

Coatings available

Nine coating and surface processes are documented in this library.

CoatingDetail page
Electroplated Zinc (Zn)Electroplated Zinc (Zn)
Yellow ZincYellow Zinc
Hot-Dip GalvanizingHot-Dip Galvanizing
Zinc Flake (Dacromet)Zinc Flake (Dacromet)
Black OxideBlack Oxide
PhosphatePhosphate
PassivationPassivation
Chromium PlatingChromium Plating
Nickel PlatingNickel Plating
Coating selection for high-strength classes is not only a corrosion question: some electroplating processes must be reviewed for hydrogen embrittlement. The coating pages carry the specific limits.

Selection by environment

The pairing this library can actually support, environment by environment.

Service environmentMaterial family this library offersCoating
Indoor, dry, controlledCarbon steelZinc, or plain where no corrosion load exists
Sheltered outdoor, humidCarbon steelZinc, zinc flake, or yellow zinc
Outdoor, weathering, longer lifeCarbon steelHot-dip galvanizing
Marine or chloride-bearingStainless A4None required, or passivation
Food, clean or wash-downStainless A2 / A4Passivation
Higher strength with corrosionAlloy steel 10.9 / 12.9Zinc flake rather than electroplating
Elevated temperatureHeat-resistant martensitic 40Cr10Si2MoPer the linked property page
Atmospheric exposure, bare steelWeathering steel (Q355GNH / A242 Type 1)None required
This table states which options this library actually carries for each environment. It is not a substitute for verifying the joint against the linked property, standard and coating pages before release.

Where to continue

Data

Mechanical Properties

Property classes and their tensile and yield values.

 Data

Surface Treatment

Coating thickness, salt spray and temperature limits.

 Data

Standards Library

Each standard also carries a materials / mechanics / surface compatibility page.

 Topic

High-Temperature Fasteners

The heat-resistant route in detail: designations, standards and failure modes.

 Topic

Weathering Steel

The atmospheric-corrosion route: patina mechanism and grade designations.