IS 1367:2002 Part 3 is the Indian Standard (BIS) for technical supply conditions for threaded steel fasteners - part 3: mechanical properties of fasteners made of carbon steel and alloy steel - bolts, screws and studs. This part of IS 1367 specifies the mechanical and physical properties of bolts, screws, and studs made of carbon and alloy steel when tested at ambient temperatures. It establishes the globally standardized property class designation system (e.g., 4.6, 8.8, 10.9) and details testing methods for assessing ultimate tensile strength, yield strength, proof load, and hardness.
Specifies the mechanical properties of bolts, screws, and studs made of carbon steel and alloy steel.
Key reference values — verify against the current code edition / project specification.
| Reference | Value | Clause |
|---|---|---|
| Property classes | 4.6 / 4.8 / 5.6 / 8.8 / 10.9 / 12.9 | Classes |
| Class code meaning | First no.×100 = UTS (MPa); ratio×UTS = yield | Convention |
| Class 8.8 | UTS ≈ 800 MPa, yield ≈ 640 MPa | Property |
| Class 10.9 | UTS ≈ 1000 MPa, yield ≈ 900 MPa | Property |
| Tests | Proof load, tensile, wedge, hardness | QC |
| Read with | IS 1367 Part 6 / IS 3757 (HSFG) / IS 800 | Cross-ref |
IS 1367 (Part 3):2002 specifies Technical Supply Conditions for Threaded Steel Fasteners — Part 3: Hot-Dip Galvanized Coatings on Fasteners. It is the coating-specification companion to the mechanical-property codes IS 1367 Parts 1-2 and the structural-bolt codes IS 1364 (hex bolts/screws) and IS 1367 (general).
Use it when: - Specifying HDG (hot-dip galvanized) fasteners for outdoor / corrosive environments — structural bolts, electrical pole hardware, transmission line fittings, marine assemblies - Verifying coating thickness on supplied fasteners — mass per unit area, magnetic gauge measurement - Investigating fastener corrosion failures — coating quality, thickness uniformity, embrittlement - Cross-referencing with metric vs imperial fastener systems — galvanizing is the great equaliser; same coating spec applies to M6, M8 ... M48 fasteners
IS 1367 series structure: - Part 1: Introduction and General Information (terminology, designation) - Part 2: Specifications and Material Properties (chemistry, mechanical properties) - Part 3: Hot-Dip Galvanized Coatings (this code) - Part 4 onwards: Various specialized topics (zinc-plated, chrome-plated, etc.)
For non-galvanized fasteners: zinc electroplating (Part 11), chromium plating (Part 14), passivation (Part 12) — each have separate Parts.
Coating mass / thickness (Clause 4):
Unlike sheet galvanizing where thickness varies with dipping time + bath chemistry, fastener galvanizing is inherently thicker because fasteners spin in the bath, allowing uniform pickup, and threads create surface area irregularities.
Minimum coating thickness for fasteners (Table 1):
| Thread diameter | Min coating mass (g/m²) | Min thickness (μm) | |---|---|---| | ≤ M6 | 28 | 4 | | > M6 to M10 | 28 | 4 | | > M10 to M14 | 35 | 5 | | > M14 to M22 | 35 | 5 | | > M22 to M36 | 50 | 7 | | > M36 | 70 | 10 |
Comparison with sheet galvanizing (per IS 277): sheets typically Z200-Z350 (25-50 g/m² per face × 2 faces = 50-100 g/m² total). Fasteners require less coating per unit area because: - Surface-to-volume ratio is much higher for sheets vs fasteners (per unit mass) - Fasteners typically have shorter exposure life requirements (structural fasteners in covered locations)
However, for outdoor / aggressive applications: specify thicker fastener coatings (e.g., double-dipping technique giving 60-80 μm coating) — used in transmission-line hardware exposed to weather for 25+ years.
Coating test methods (Clauses 6-8): - Coating mass test (Annex A): chemical method — strip the coating with HCl + dezincification inhibitor; weigh fastener before and after; difference divided by surface area - Magnetic gauge measurement: non-destructive; field-portable; measures one face at a time. Multiple readings averaged. Accuracy ± 5-10%. - Adhesion test (Annex B): bend a sample fastener over a mandrel; check no coating delamination from threads or head
Other coating requirements (Clauses 5, 9-12): - Uniformity: visual inspection — no missed spots, no flow-induced thin areas at thread root - Spangle quality: well-formed crystalline pattern; uniform; no excessive dross / drips - Surface finish after galvanizing: not 'bright' (that's electroplating); 'matt grey' to 'spangled metallic' acceptable - Marking: each batch must carry IS 1367 reference and BIS approval mark
Galvanized fasteners can suffer hydrogen embrittlement — a brittle failure mechanism where atomic hydrogen absorbed during the pickling/galvanizing process makes the fastener prone to delayed brittle fracture under sustained tensile stress.
Risk factors: - High-strength fasteners (Property Class ≥ 10.9 per IS 1364 / ISO 898-1): most susceptible. The 12.9 class is prohibited from HDG galvanizing in IS 1367 Part 3 — embrittlement risk too high - Acid pickling step: deep cleaning before galvanizing releases atomic hydrogen into the steel - Slow cooling after dipping: traps hydrogen - Stress concentrators: thread roots, head-to-shank fillets — hydrogen migrates here and initiates fracture
IS 1367 Part 3 mitigations (Clause 7): - Baking after galvanizing at 200-230°C for minimum 4 hours for property class 10.9+ fasteners — releases absorbed hydrogen - Direct sponsoring with PB pellets (lead-bath galvanizing) for ultra-low-hydrogen applications - Mechanically galvanizing (zinc cold-shot method, Part 13) is an alternative — no acid pickling, no hydrogen
Field observation: hydrogen embrittlement failures typically occur 24-72 hours after tightening, not immediately on installation. A bolt looks fine when torqued; head pops off under sustained service load within days.
For HDG fasteners in critical applications (structural connections, lifting equipment, pressure vessels): mandate post-galvanizing baking certificate per IS 1367 Part 3 Clause 7. Without this, brittle failure risk is real.
1. Specifying HDG for property class 12.9 fasteners — prohibited. 12.9 fasteners must use mechanical galvanizing (Part 13) or zinc-aluminium flake coatings (Geomet, Dacromet) to avoid embrittlement. HDG-coated 12.9 bolts have failed catastrophically in service.
2. Insufficient post-baking — Property Class 10.9 fasteners must be baked 4+ hours at 200-230°C after galvanizing. Many small galvanizing job-works skip this; failure rate jumps from < 0.1% to 5-15%.
3. Using cut-off galvanized bolts — fasteners cut to length AFTER galvanizing have exposed steel at the cut end. Steel rusts; rust creeps under the coating; eventual coating failure. Always specify pre-cut and galvanized fasteners; for cut-on-site, apply zinc-rich paint on the cut end.
4. Mixing zinc-coated with carbon-steel washers — galvanic couple in damp environment. Always use galvanized washers + galvanized bolts together; never mix.
5. Inadequate coating thickness verification — magnetic gauge cheap to use; takes 30 seconds per fastener; gives reading in μm. Not verifying on a sample of received fasteners means you don't actually know what coating you've procured.
6. Re-tightening galvanized fasteners — galvanizing coats threads + reduces effective contact area; coefficient of friction is higher than non-galvanized. Tightening torque must be reduced by 20-30% from carbon-steel values. Excessive torque cracks the coating, fractures the bolt.
7. Using fasteners with non-conforming spangle pattern — uniform crystalline spangle indicates proper bath chemistry. Mottled / patchy pattern indicates poor process control; underlying coating thickness may be insufficient.
8. Specifying 'HDG' without ISO 1367 reference — global suppliers ship to various standards (ASTM A153, EN ISO 10684, ISO 10684). Cross-reference: ASTM A153 Class C ≈ ISO 10684:2004 with comparable thickness. IS 1367 Part 3 is broadly aligned with ISO 10684.
IS 1367 Part 3:2002 is 23 years old but remains the working spec. The 2002 revision aligned with ISO 10684 international practice. Minor amendments since (most recent 2018) have refined acceptance test methods. No major revision in sight.
Procurement reality: - Premium HDG fasteners (Pranav Construction, Sundram Fasteners, Lakshmi Machine Works): IS 1367 Part 3 compliant, hydrogen-free, full traceability. Pricing ₹400-600/kg for M16-M24 structural bolts; ~30-50% premium over non-galvanized. - Mid-market: Indian and imported (Chinese, Korean) HDG fasteners. Coating mass varies by 30-40% between suppliers. Pre-qualify with sample testing. - Budget / unbranded: HDG fasteners stamped 'IS 1367' but actual coating 50-60% of spec; hydrogen embrittlement frequent. Avoid for critical structural applications.
For structural / lifting / safety-critical applications: - Specify IS 1367 Part 3 + property class + coating thickness - Mandate Material Test Certificate + Coating Test Certificate per batch - For class 10.9+: insist on post-galvanizing baking certificate - Magnetic gauge verification of 5-10% of delivered fasteners
Service life expectations: - IS 1367 Part 3 standard coating (50-70 g/m² average): 15-25 years in inland Indian climate; 8-15 years coastal - Double-dipped or specialty thick coatings: 25-50+ years - Mechanical galvanizing (Part 13): similar performance, no embrittlement risk - Zinc-aluminium flake coatings (Geomet, Dacromet): premium pricing but excellent for severe environments + Class 12.9 use
Cost vs life-cycle calculation: HDG fasteners cost 30-50% more than zinc-electroplated, last 5-10× as long. For permanent / outdoor / structural applications, HDG is always cost-effective on life-cycle basis. Only for indoor / replaceable / temporary use does electroplating make economic sense.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Ultimate Tensile Strength (UTS), Class 8.8 (d > 16mm) | 830 MPa (min) | 830 MPa (min) | ISO 898-1:2013 |
| Yield Strength (ReL or Rp0.2), Class 8.8 | 640 MPa (min) | 640 MPa (min) | ISO 898-1:2013 |
| Proof Load Stress (Sp), Class 10.9 | 830 MPa | 830 MPa | ISO 898-1:2013 |
| Hardness (Vickers), Class 10.9 | 320-380 HV | 320-380 HV | ISO 898-1:2013 |
| Percentage Elongation after Fracture (A), Class 8.8 | 12% (min) | 12% (min) | ISO 898-1:2013 |
| Charpy Impact Strength (KV) for Class 10.9 (d > 16mm) | 30 J at -40°C (if specified) | 27 J at -20°C (mandatory unless from low carbon martensitic steel) | ISO 898-1:2013 |
| Hardness (Vickers), Class 12.9 | 385-435 HV | 385-435 HV | ISO 898-1:2013 |