49 CFR §193.2629

1. (a)Each buried or submerged component that is subject to external corrosive attack must be protected from external corrosion by—
   1. (1)Material that has been designed and selected to resist the corrosive environment involved; or
   2. (2)The following means:
      1. (i)An external protective coating designed and installed to prevent corrosion attack and to meet the requirements of § 192.461 of this chapter; and
      2. (ii)A cathodic protection system designed to protect components in their entirety in accordance with the requirements of § 192.463 of this chapter and placed in operation before October 23, 1981, or within 1 year after the component is constructed or installed, whichever is later.
2. (b)Where cathodic protection is applied, components that are electrically interconnected must be protected as a unit.