Stud Bolts, Nuts, Screws, Threaded Rod & Washers
This Specification outlines the requirement for Bolt and nut coating for onshore and offshore oil and gas facilities including subsea applications.
We at Torqbolt provide the following detailed coating system of Stud Bolts and Nuts operating at temperature below 200°C:
Basecoat( First Coat) which provides resistance of Zinc Nickel Plating as per ASTM B841/F1941 or ISO 4042/10576 with an average thickness of 10-18µm.
TopCoat ( Second Coat) PTFE POLY TETRA FLUORO ETHYLENE based Whitford Xylan coating namely Xylan 1014, Xylan 1070, Xylan 1424 or Dupont Teflon 174 SBC
We hereby suggest to used the above specified combination of base coat and top coats for the following grades
STUD BOLTS ASTM A193/A193M & ASTM A320/A320M HEAVY HEX NUTS ASTM A194/ A194M
Mechanical cleaning and /or chem ical treatments shall be used to produce a satisfactory surface for subsequent plating/ deposition and finish coating, i.e. free from soils, environmental matter, drawing compounds, oil grease, discolouration oxides, scale and other foreign matter. Materials used for cleaning shall have no damaging effects on the base metal. Surface Preparation Of Zinc Nickel Plating shall comply to ASTM B322 and B183 and must include the following
Zinc Nickel alloyed coating deposited from an alkaline; cyanide free; electrolyte shall have a composition of the coating to be in the range of 12-18% Nickel balance being Zinc. The bolting materials coated with Zinc Nickel alloyed coating shall be phosphate treated in accordance with ASTM D 2092, Method A (12-18 µm) or equal. The phosphate treatment is to ensure basecoat is adherent to topcoat . The general plating process shall be as per below:
A PTFE based coating shall be applied as secondary coating corrosion barrier and to reduce torque-up friction during installation. The general coating process shall be as per below: