Bolting exposed directly to a sour environment or that is buried, insulated, equipped with flange protectors, or is otherwise denied open atmosphere or open seawater exposure.
Source: API Specification 16A, Specification for Drill-through Equipment, Fourth Edition, April 2017. Global Standards
Bolting that is exposed directly to the sour environment or that is buried, insulated, equipped with flange protectors, or otherwise denied direct atmospheric exposure.
Source: API SPEC 6A, Specification for Wellhead and Christmas Tree Equipment, Twentieth Edition, October 2010 (Addendum November 2012). Global Standards