Threaded hardware used at diver depths

[awol]

What is the preferred coating for threaded fasteners used in seawater at depths where divers work? No ROVs. Have used Teflon coated fasteners (nuts, studs) but some speculate that the Teflon coating is damaged as torque is applied. Nitriding the hardware has been suggested but not confirmed as the best solution for seawater. Hardware will be assembled and tightened to a torque value underwater.
Thanks, awol

 

[StephenA]

One way is to galvanise but this depends on the application. The threads are overcut, then the bolts and nuts are galvanised, then the threads are cleaned with standards dies and taps. Probably no good with fine threads.

Otherwise use waterproof grease and wrap the fitting afterwards

Stephen Argles
Land & Marine

http://www.landandmarine.com

 

[narenr]

All coatings are prone for damage during torquing. For subsea applications, bolts are either PTFE or Teflon coated. The concern is not more on coating damage but more on slipping.

Rgds Naren

Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.

 

[BillBirch]

awol, (get back to work heh, heh)
I believe that there is a range of quality in PTFE coated fasteners, based on their sub-layer. I recall different systems employing various plating under the coating such as cadmium or nickel etc. Perhaps if you research this variety you may find an optimum selection.
Regards,
Bill