Petrochemical Bolt Coatings: Mechanical Plating, Zinc Silicate, Moly and Xylan

Key things to remember

The essentials from this document in plain words. Check the full document before you rely on a figure.

• ✓Mechanical plating is recommended for high tensile fasteners such as the petrochemical and Sampsonrod range, up to 2 inch diameter and 14 inch long, with no hydrogen embrittlement and no blocked threads.
• ✓Inorganic zinc silicate is for extreme corrosive environments: items are sandblasted to a Class 3 finish, then given 25 to 35 micron of zinc, with corrosion protection up to 2,000 hours.
• ✓1PX1 (moly) builds the thread lubricant into the fastener, cutting friction so fasteners tension evenly, resists corrosion up to 350°C and makes nuts easier to remove in maintenance.
• ✓Xylan 1424 series (blue and green) gives under 15% red rust after 1,488 hours salt spray, cuts make-up torque by as much as 70% and works from minus 40°C to 205°C.
• ✓Nuts are coated internally with the moly and Xylan coatings. Other coatings listed: cadmium, phosphate and oil, PTFE, fluorocarbon, hot dip galvanised and zinc plate.

Who it helps: Engineers and buyers specifying coated stud bolts and nuts for corrosive or high temperature plant.