Each component [any part, or system of parts functioning as a unit, including, but not limited to, piping, processing equipment, containers, control devices, impounding systems, lighting, security devices, fire control equipment, and communication equipment, whose integrity or reliability is necessary to maintain safety in controlling, processing, or containing a hazardous fluid] that
is subject to internal corrosive attack must [used in the mandatory and imperative sense]
be protected from internal corrosion by-
(a) Material that has been designed and selected
to resist the corrosive fluid involved; or