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answered May 16, 2016 by abuHaferssas (320 points)
Bolting material should meet the following minimum requirements:

· All carbon steel bolts, studs, and nuts should be coated with Xylan (or similar approved coating) for corrosion protection.  Electro-deposited Zinc Plating is an approved coating.  The chosen coating is acceptable only if electrical continuity to the cathodically protected structure is confirmed with a test after assembly.

· Bolts, studs, and nuts manufactured from carbon or alloy steel should not be used in subsea service at hardness levels exceeding 35 Rockwell C.

· Bolts, studs and nuts for all structural components should satisfy all of the requirements of ASTM A 193/A 193M Gr B7, B7M, L7, or Grade 660 SS with a hardness not exceeding 35 Rockwell C, as specified in API SPEC 17D.

· Bolts, studs, and nuts for pressure containing and pressure controlling equipment should satisfy the requirements of NACE MR0175.