49 CFR §192.463

1. (a)Each cathodic protection system required by this subpart must provide a level of cathodic protection that complies with one or more of the applicable criteria contained in appendix D of this part. If none of these criteria is applicable, the cathodic protection system must provide a level of cathodic protection at least equal to that provided by compliance with one or more of these criteria.
2. (b)If amphoteric metals are included in a buried or submerged pipeline containing a metal of different anodic potential—
   1. (1)The amphoteric metals must be electrically isolated from the remainder of the pipeline and cathodically protected; or
   2. (2)The entire buried or submerged pipeline must be cathodically protected at a cathodic potential that meets the requirements of appendix D of this part for amphoteric metals.
3. (c)The amount of cathodic protection must be controlled so as not to damage the protective coating or the pipe.