What Is Xylan Coating?

Xylan is a proprietary fluoropolymer coating system (manufactured by Whitford Corporation) applied to stud bolts, nuts, fasteners, and valve components to provide corrosion protection, reduced friction, and anti-galling properties. The coating consists of a PTFE/fluoropolymer matrix bonded to the substrate with an organic or inorganic primer, applied as a spray or dip and cured at elevated temperature.

Xylan Coating Grades

Grade	Type	Color	Max Temp	Typical Application
Xylan 1070	Fluoropolymer/organic binder	Blue, green, black, custom	260°C (500°F)	General-purpose bolt coating; most common
Xylan 1424	Fluoropolymer/organic binder	Silver, grey	260°C (500°F)	High-corrosion environments; offshore bolting
Xylan 1014	Fluoropolymer/organic binder	Various	260°C (500°F)	Valve stems, actuator components
Xylan 8840	Fluoropolymer/inorganic binder	Dark grey	400°C (750°F)	High-temperature bolting; refinery service

The typical dry film thickness is 20-40 micrometers (0.8-1.5 mils). The coating does not significantly affect bolt thread dimensions or fit.

Why Xylan on Bolts?

The primary benefits for flange bolting are:

Benefit	Explanation
Reduced nut factor (K)	Xylan reduces the friction coefficient to approximately 0.10-0.12, compared to 0.20 for bare steel and 0.15 for moly-lubricated bolts
Consistent torque-to-tension	Lower and more predictable friction means more uniform bolt load across the flange
Corrosion protection	Fluoropolymer barrier resists atmospheric corrosion, salt spray, and chemical exposure
Anti-galling	Prevents thread seizure during assembly and disassembly, especially for stainless steel and alloy bolts
Disassembly after service	Bolts coated with Xylan can be removed years after installation without cutting or heating

Common Mistake

Using torque values designed for bare (unlubricated) bolts on Xylan-coated bolts will over-tension the studs; potentially exceeding yield strength and cracking the flange. Always adjust bolt torque values for the actual nut factor of the coated bolt. A K factor of 0.10 (Xylan) vs. 0.20 (bare) means the same torque produces approximately double the bolt load.

Xylan vs. Other Bolt Coatings

Coating	Friction (K factor)	Corrosion Resistance	Max Temp	Cost
Xylan 1070	0.10-0.12	1,000+ hrs salt spray	260°C	Medium
PTFE spray	0.08-0.12	500 hrs salt spray	260°C	Low-Medium
Hot-dip galvanizing	0.18-0.22	500+ hrs salt spray	250°C	Low
Zinc phosphate + oil	0.15-0.18	200 hrs salt spray	200°C	Low
Cadmium plating	0.10-0.13	500+ hrs salt spray	230°C	High (restricted use)
PTFE-impregnated Dacromet	0.10-0.14	1,000+ hrs salt spray	300°C	Medium-High

Application Process

1. Surface preparation: grit blasting to Sa 2.5 (near-white metal) per ISO 8501-1
2. Primer application: spray or dip primer coat (inorganic zinc or organic binder)
3. Primer cure: oven cure at 150-200°C
4. Topcoat application: spray or dip fluoropolymer topcoat
5. Final cure: oven cure at 200-260°C (depending on grade)
6. Inspection: verify dry film thickness (20-40 micrometers), adhesion, and visual appearance

Pro Tip

For NACE sour service projects, verify that the Xylan coating process does not affect the base material hardness. The curing temperatures (200-260°C) are below the tempering range of A193 B7 bolts (minimum tempering at 593°C), so there is no risk of hardness change. However, the coating must be applied after final heat treatment.

Xylan coatings are specified in major EPC projects by referencing the Whitford grade number and color in the bolting specification. For subsea and offshore applications, additional requirements per NORSOK M-501 or ISO 12944 may apply to the coating system.

Read the full guide to steel corrosion