Whitford QAC Approved Coater · API 20E (BSL 1/2/3)

Extreme-Duty Fastening & Advanced Surface Engineering

Integrated manufacturing, thermal diffusion Sheradizing, and high-performance fluoropolymer Xylan® coating systems for severe marine, offshore subsea, chemical processing, and cryogenic environments.

Request Technical Spec & Quote Compare 8 Coating Systems

Salt Spray Life

5,000+ Hrs

Annual Capacity

5,000 t/yr

Plant Footprint

8,000 m²

Quality Audits

ISO 9001/18001

Worldwide QAC
API

API Spec 20E Qualified

BSL-1, BSL-2, and BSL-3 Bolting for Oil & Gas

Zero Hydrogen Embrittlement

Sheradizing thermal alloy layer: no acid pickling, zero embrittlement

100% Fitment Gauged

Precision ring & plug thread inspection post-coating application

Traceable EN 10204 3.1 / 3.2 MTC Norsok M650 Compliant
Scope of Supply

Heavy Industrial Fastener Series

Engineered for high clamping load integrity under severe shear, tension, and cryogenic/thermal cycling. Available from standard ISO metric/imperial threads up to custom non-standard project fabrications.

Heavy Hex Head Bolts and Structural Studs High Tensile

Bolts & Threaded Studs

  • Hex head bolts & screws
  • High-strength structural bolts
  • Full thread stud bolts & double-end studs
  • Socket head cap & set screws
  • Welded studs & anchor bolts
ASME B18.2.1 · DIN 933 · ISO 4014
Heavy Hex and Locking Nuts Proof Load Tested

Heavy Hex & Lock Nuts

  • Finished regular hex nuts
  • Heavy hex nuts (high clamping)
  • High-strength structural steel nuts
  • All-metal & nylon insert lock nuts
  • Slotted & castle flange nuts
ASME B18.2.2 · ISO 4032 · DIN 934
Direct Tension Indicators and Precision Washers Preload Control

Washers & DTI Systems

  • Hardened plain & flat washers
  • Helical spring lock washers
  • Square taper / beveled channel washers
  • Direct Tension Indicators (DTI)
  • EN 14399 preload washer assemblies
ASTM F436 · DIN 125 · EN 14399-6
Pipeline U-Bolts and Custom Fasteners API 20E Qualified

U-Bolts & API 20E Bolting

  • Standard & long tangent U-bolt sets
  • Pipeline saddles & clamp sets
  • Vibration / insulation rubber clamp sets
  • API Spec 20E BSL 1, BSL 2, BSL 3 bolting
  • Client OEM non-standard custom drawings
API 20E · DIN 3570 · Customized

Supported Dimension & Manufacturing Standards

DUROX production tooling is calibrated across major industrial territorial standards:

ASME B18.2.1 / B18.2.2 ISO 4016 / 4017 / 4032 DIN 933 / 934 / 975 GOST R 52643 / 52644 GB / HG / SH / NB / JB
Alloy Matrix

Certified Raw Materials & Heat Treatment

From low-temperature subsea applications (-196°C) to high-pressure thermal reactors (up to 700°C). Full positive material identification (PMI) conducted on every incoming billet.

Inspection: Spectral Chemical & V-Notch Impact

High-Tensile & Low-Temp Bolts

ASTM A193: Gr. B7, B7M, B16 (High-temp, high-pressure service)
ASTM A320: Gr. L7, L7M, L43 (Low-temp subsea impact tested at -101°C / -150°C)
Structural & Anchor: ASTM A325/A325M Type 1, A490/A490M Type 1, F1554 Gr. 36/55/105, A307 Gr. A/B
Property Classes: ISO 898-1 / GB 3098-1 / GOST R 52627: Gr. 4.8, 5.6, 5.8, 8.8, 10.9, 12.9; ASTM A540 B21-B24; 30CrMo / 35CrMo

Matching Nut Specifications

ASTM A194: Gr. 2H, 2HM, 4, 7, 7M (Quenched & tempered heavy hex)
ASTM A563 & A563M: Gr. O, A, B, C, D, DH, DH3; Metric 5, 9, 8S, 10S, 12, 8S3, 10S3
ISO 898-2 / GB 3098-2: Gr. 4, 5, 8, 10, 12; GB/T 1231 Gr. 8, 10
Engineering Note: B7M & L7M grades are 100% hardness tested to max 22 HRC to satisfy NACE MR0175/ISO 15156 sour gas environments.
Comprehensive Benchmarking

Sheradizing vs. Conventional Surface Treatments

Detailed engineering comparison matrix covering 8 standardized fastener protective systems. Analyze thickness buildup, hydrogen embrittlement liability, thread fitment, and neutral salt spray (ASTM B117) durability.

Engineering Parameter Zn-Plating Zn + Xylan® Zn-Ni Plating Zn-Ni + Xylan® Xylar® 2 + Xylan® HDG (Hot Dip) Mechanical Zn Sheradizing (DUROX)
Coating Thickness 8-13 μm 23-38 μm 8-13 μm 23-38 μm 35-55 μm 45-120 μm 25-110 μm 15-85 μm (Controlled)
Corrosion Life Short Comparatively Long Long Comparatively Long Comparatively Long Long Normal Extra Long (Alloy bond)
Hydrogen Embrittlement Risk Present (Yes) Eliminated (No) Risk Present (Yes) Eliminated (No) Eliminated (No) Low/Moderate None (No) Zero Risk (No Acid)
Component Strength Loss No No No No No Possible (High Temp) Possible No (Low Diffusion Temp)
Thread Fitment / Clearance Negligible Minor Negligible Minor Minor Severe (Requires overtap) Minor Uniform Profile Followed
Adhesion Level Good Good Good Good Good Good Poor Superior (Fe-Zn Interdiffusion)
Coating Uniformity Good High Precision Good High Precision High Precision Very Poor (Root clogging) Moderate Excellent (True to Pitch)
U-Bolt Applicability Good Good Good Good Good Poor (Flaking at bend) Poor Optimal (Zero Flaking)
ASTM B117 Salt Spray 96 Hrs 2,500 Hrs 5,000 Hrs 5,000 Hrs 5,000 Hrs 2,500 Hrs 2,500 Hrs 5,000 Hrs
Cost / Price Index Economical Moderate High Premium High Tier Economical Economical Cost-Effective

* Data compiled in accordance with standard ASTM B117 neutral salt fog test procedures and ISO 14713 atmospheric durability categories.

Thermal Diffusion Technology

High Quality Sheradizing Process

Sheradizing is a micro-diffusion process where zinc vapor penetrates the steel matrix inside sealed, rotating drums at 380°C-450°C. It generates a multi-phase Zinc-Iron alloy layer that chemically fuses with base carbon and alloy steel.

Sacrificial Passive Anode: Serves as a dense barrier insulating the substrate steel from marine immersion, acidic atmospheres, and atmospheric condensation.
Extreme Surface Hardness: Reaches microhardness up to 400-550 HV, yielding higher anti-galling, scratch resistance, and abrasion endurance than soft electroplated zinc.
100% Acid-Free Process: Abrasive blast cleaning replaces acid pickling. Zero hydrogen absorption guarantees total elimination of catastrophic hydrogen embrittlement in Grade 10.9 & 12.9 bolting.
DUROX automated sheradizing thermal diffusion facility
Fe-Zn Metallurgical Interlayer ASTM A1059 / BS EN 13811
Robotic Xylan Spraying Facility at DUROX
Whitford Worldwide QAC Licensed Coater Xylan 1424 / 1014 / 1070
Fluoropolymer Thin Film Technology

High Performance Xylan® Coatings

Since 2002, DUROX has partnered with Whitford (PPG) to engineer multi-layer composite fastener systems. Combining bonded zinc or zinc-nickel bases with Xylan 1000/1400 series fluoropolymer top coats creates an economic, high-integrity alternative to solid Hastelloy and Monel fasteners.

Low Friction & Stable Torque: Friction coefficient 0.04-0.08 ensures consistent clamp preload without galling.
Chemical Shielding: Immune to 5% sulfuric acid, 5% acetic acid, caustic washdowns, and saltwater spray.
Thermal Stability: Continuous working range from -195°C cryogenic service up to +285°C (+550°F).
Available Pigmentation: Marine Blue, Signal Green, High-Visibility Yellow, Crimson Red, Deep Black.
Quality Assurance Architecture

In-House Testing & Verification Facilities

Full traceability guaranteed from steel ladle chemistry through final packaging. Our on-site physical and metallurgical testing laboratory operates in compliance with ISO/IEC 17025 practices.

01

Coating & Chemical Lab

Continuous verification of cured film performance:

  • • MEK Solvent Rub Rub-off cure verification
  • • ASTM D3359 Cross-hatch adhesion
  • • Dry Film Thickness (magnetic induction)
  • • 5% H2SO4, 5% CH3COOH, 5% NaHCO3 spot dip
  • • Dual ASTM B117 automated salt fog chambers
02

Mechanical Integrity

Rigorous load capability testing for high-tensile bolting:

  • • 1000 kN Universal Tensile & Proof Load
  • • Wedge tensile and axial proof stress tests
  • • Low-temp Charpy V-notch impact down to -196°C
  • • Rockwell C & King 3000 Brinell Hardness
  • • Micro-hardness Vickers (HV0.3) layer check
03

NDT & Thread Gauging

100% fit-up certainty on site without recutting:

  • • 100% GO/NO-GO Thread Ring & Plug Gauging
  • • Optical comparator thread pitch inspection
  • • Magnetic Particle Inspection (MT)
  • • Liquid Penetrant Testing (PT)
  • • Ultrasonic flaw detection on heavy diameters
04

Process Equipment

Advanced machinery maintaining statistical capability (SPC):

  • • UK DeVilbiss High-Precision Spray Guns
  • • ZAHN #3 Calibrated Viscosity Flow Cups
  • • Digital hygrometers & dew-point sensors
  • • Eco-friendly continuous convection curing kilns
  • • Nitrogen atmosphere annealing furnaces
Engineering Inquiries

Frequently Asked Technical Questions

Practical design considerations for selecting protective coatings on critical bolting assemblies.

Why choose Sheradizing over Hot-Dip Galvanizing (HDG) for structural and U-Bolts?
HDG creates excessive, uneven puddle accumulations in the thread roots (45-120 μm) that require thread chasing or overtapping nuts, which strips the protective zinc coating from the mating engagement. Sheradizing produces a metallurgical Fe-Zn diffusion layer that follows the exact thread geometry uniformly (15-45 μm) without overtapping. Additionally, Sheradizing involves zero acid pickling, removing the threat of hydrogen embrittlement on high-tensile steels (Grade 10.9, B7, L7).
Can Xylan® coated studs replace costly exotic alloy bolts in offshore projects?
Yes. In many splash-zone and atmospheric platform applications, using high-strength low-alloy steel (such as ASTM A193 B7 or A320 L7) primed with Zn-Ni plating or Sheradizing and top-coated with Whitford Xylan 1424 delivers 2,500 to 5,000 hours of ASTM B117 salt spray performance. This composite system prevents galling on makeup and breakout while slashing fastener raw material acquisition costs by up to 60% compared to solid Inconel 625 or Super Duplex S32750.
What quality documents and mill test certificates accompany each shipment?
Every shipment includes an EN 10204 Type 3.1 inspection certificate (with 3.2 available on third-party witness request via DNV, Lloyd's, or ABS). Documentation includes chemical heat analysis, mechanical tensile/yield/elongation data, sub-zero Charpy V-notch values, coating thickness measurement logs, Whitford QAC batch certificates, and dimensional compliance records.
What is the torque factor (k-factor) modification for Xylan® coated fasteners?
Due to the integrated PTFE dry film lubricant, the nut factor (k) for Xylan coated fasteners typically ranges from 0.12 to 0.15, compared to 0.20+ for plain as-received steel. Engineering tightening torque must be calculated according to these lower friction numbers to achieve the intended bolt tension preload without over-stressing the bolt shank.
Direct Engineering Contact

Request Fastener Quote & Specification Support

Submit your Bill of Materials (BOM), required dimensional standards, steel grade, and corrosion coating requirements. DUROX engineers respond within 24 hours.

Strict confidentiality assured. Non-Disclosure Agreement (NDA) supported upon request.

DUROX INDUSTRIAL FASTENERS CO., LTD.

ISO 9001:2015 · ISO 14001 · OHSAS 18001 · Whitford Quality Approved Coater (QAC)

EN 14399 High-Strength Preload NORSOK M650 Qualified API Spec 20E (BSL 1-3)