Surface Coatings &Head Stamp Decoder
Surface plating specifications, corrosion-resistance and hydrogen-embrittlement guidance, plus an identification decoder for fastener head-stamp markings (ISO 898-1, ASTM, SAE J429).
Fastener Platings & Corrosion Resistance
6 coating options with standard, thickness & performance
Immersion Zinc Coating · Matte Dull Gray
Standard: ISO 10684 / ASTM A153 / ASTM F2329
Recommended for: Outdoor infrastructure, civil bridges, coastal substations, highway guardrails, transmission towers.
Electrolytic Zinc Passivation · Bright Silver / Blue Iridescent
Standard: ISO 4042 / ASTM F1941 Fe/Zn 5-8
Recommended for: Indoor electrical cabinets, consumer machinery, dry sheltered mechanical assemblies.
Electrolytic Zinc Trivalent Yellow · Golden Iridescent Yellow
Standard: ISO 4042 / ASTM B633 Type II
Recommended for: Automotive underbody brackets, agricultural machinery, construction scaffolding.
Resin-Bonded Ceramic Fluoropolymer Barrier · Marine Blue / Green / Yellow
Standard: ASTM F3393 / NACE SP0108
Recommended for: Subsea oil & gas trees, offshore splash zones, sour gas valves, chemical refinery flanges. Extremely low friction coefficient (µ = 0.06 - 0.08).
Non-Electrolytic Inorganic Zinc-Aluminum Flake · Metallic Silver
Standard: ISO 10683 / ASTM F1136 Grade 3
Recommended for: High tensile fasteners (Grade 10.9 & 12.9) where hydrogen embrittlement must be 100% avoided; automotive chassis and disc brake mounting.
Chemical Conversion Coating (Magnetite Fe3O4) · Deep Matte Black
Standard: MIL-DTL-13924 / DIN 50938
Recommended for: Precision machine tool components, indoor socket head screws, tooling fixtures requiring zero dimensional buildup.
Head Stamp & Identification Marking Decoder
Identify fastener material grade from its head marking (11 grades)
Marking: 8.8 + Manufacturer Logo
Stamped "8.8" on the top of the hex head with the maker trademark.
Material: Medium carbon steel, quenched and tempered
Marking: 10.9 + Manufacturer Logo
Stamped "10.9" on the top of the hex head with maker logo.
Material: Alloy steel (e.g. 40Cr / 42CrMo), quenched and tempered
Marking: 12.9
Stamped "12.9" on head rim or inside Allen socket recess.
Material: High-alloy steel, quenched and tempered to high hardness
Marking: A2-70
Stamped "A2-70" denoting Austenitic Grade 2 (AISI 304) with 700 MPa tensile strength.
Material: Austenitic Stainless Steel AISI 304 (18Cr-8Ni)
Marking: A4-80
Stamped "A4-80" denoting Marine Grade 4 (AISI 316) cold worked to 800 MPa tensile.
Material: Austenitic Stainless Steel AISI 316 with 2-3% Molybdenum
Marking: A325 (Type 1 or Type 3)
Raised or indented letters "A325" on the heavy hex head.
Material: Structural high strength medium carbon alloy steel
Marking: A490
Raised or indented "A490" on the heavy hex head.
Material: Alloy steel quenched and tempered (not permitted to be hot-dip galvanized)
Marking: B7 (Stamped on stud end)
Stamped "B7" on one end of continuous all-thread stud along with manufacturer mark.
Material: AISI 4140 / 4142 Chromium-Molybdenum high-temp alloy steel
Marking: 2H (or 2HB if Brinell tested)
Stamped "2H" on bearing face or top chamfer of heavy hex nut.
Material: Quenched & tempered carbon steel heavy hex nut for high pressure/temp
Marking: 3 Radial Slash Marks at 120°
3 raised radial lines spaced at 120 degrees around the hex head.
Material: Medium carbon steel, quenched and tempered
Marking: 6 Radial Slash Marks at 60°
6 raised radial lines spaced at 60 degrees around the hex head perimeter.
Material: Medium carbon alloy steel, quenched and tempered