GOODEVNING,
the calculation of a cathodic protection sytem depends at first to the objet to protect (its material, dimensions, geometry, caoting ), at second of the envirnement (soil, sea, river…).
the envirnement is catactrise with its resistivity, if the resitivity is too low, and if its caot isn't made of lagging, and if its the electrolyt isn't sufuric acid then you can protect the objet with a system of cathodic protection.
th e calculation depends en the external surface of the objet and ist type of coating.
there's same vlaues isccated in nace standards or europeen standards that give you grid of values to use in calculation of cathodic protection