PTFE Xylan Coating Specification.
Xylan or fluoropolymer Coating is a common coating method for the stud bolt,hex nuts,and other fasteners which required high anti -corrosion ,anti-rust in critical enviorement.The coating quality is very important for the stud bolt performance.
You would find the manufacturing and documentation requirements for fasteners of nominal size M12 (1/2”) and larger being coated with Xylan® and requiring a certified material test report of EN 10204 3.1
Manufacturing of fasteners to be Xylan® coated
The thickness of the coating to be applied shall be taken into account when manufacturing the Stud bolt subject to coating, as the application of coatings affects the fastener dimensions.
Pls refer to the coating thickness recommend in our specification.
Pre-treatment
Degreasing
1.1 The uncoated fasteners shall be thoroughly cleaned, as to remove all traces of grease, oil and other contaminations.
1.2 Recommended degreasing processes are:
2.1 Bake-out at 380-400°C (716-752 °F) for a minimum of 3 hours.
2.2 Hot alkali degreaser plus water wash.
2.3 Chlorinated hydrocarbon solvent.
2.1 Before coating, all fasteners shall be tumbled or shot blasted with suitable equipment to ensure a clean, scale-free, chemically active surface. Minimum requirement SSPC SP5 or DIN EN ISO 12944-4. Thread damage is not acceptable.
2.2 Abrasive shall be new aluminum oxide or stainless steel sufficient to produce a minimum 5 micron surface profile. The abrasive shall be clean and dry, storage according manufacturer
Subsequent processing shall be carried out within the time frame recommended by PPG Whitford.
Post-Cleaning
After blasting, the components shall be cleaned by air blasting using oil free, dry air or solvent
washing, to remove traces of debris and dust prior to subsequent processing.
Base Coat
Depending on the base material and the intended application, different base coats have to be applied on the fastener material prior to the Xylan® coating. The type, thickness and quality of the base coat, shall be as stated in the PO;
In general, Stud bolts made of carbon- and low alloy steel(ASTM A193 B7/B7M ,A320 L7/7M) will receive a base coat consisting of either a zinc phosphate conversion coating or a zinc or zinc-nickel electroplating. In order to increase the corrosion resistance further, a hexavalent or trivalent chromium conversion layer may be applied on the base coat.
Stud bolt made of Stainless steels(ASTM A193 B8/B8M) usually do not require a base coat. For improved corrosion resistance, the primer coatings Xylan® 4090, Xylar®-1 or Xylar®- 2 may be applied prior to the final Xylan® coating.
Application of Xylan®/ Xylar® Coating
The fasteners shall be coated with the grade of composite fluoropolymer-/ceramic coating stated in the PO
Thickness of Coats
Each layer has to be applied with a dry film thickness (DFT) of 20±5µm (1±0.2 mil). The total coating thickness (DFT) shall be not less than 30 µm (1.2 mil) and not more than 45µm (1.8 mil) unless a different coating thickness is specified
Curing Cycles
Curing Cycles (heating rate, soaking temperature and time at temperature) shall be in accordance with the latest Manufacturer’s Product Data Sheet.
Inspection and Testing
Visual Inspection
Dimension
Adhesion Testing
Dry Film Thickness (DFT)
Dry film coating thickness on flat surfaces shall be determined using a properly calibrated (in accordance with DIN EN ISO 19840 or SSPC PA2) eddy current type coating thickness gauge.
Want to learn more about PTFE Xylan coated stud bolt
How to select the most suitable xylan coating material for your applications.
Learn more about Xylan specifications? Xylan Coating Material Selections.
