Internal cathodic protection by resistor controlled anodes - Resistor controlled Cathodic Protection (RCP) - has been introduced as an alternative method for the prevention of localised corrosion of seawater transportation systems. More than 1000 RCP anodes have been installed in seawater piping systems made from highly alloyed stainless steel which previously had suffered from corrosion. The application of cheaper stainless steels like AISI316 in combination with RCP anodes results in significant cost savings for the seawater system, and a few systems have been installed. This paper gives a short review of the theoretical background, and a presentation of the experience from some of the installations with these materials and RCP. Keywords ; Stainless steel, cathodic protection, seawater, resistor controlled cathodic protection.