FSM is a non-intrusive monitoring technique based on a patented principle, developed for the purpose of detection and monitoring of both general and localized corrosion, erosion and cracking in steel and metal structures, piping systems and vessels. Since 1991 FSM has been used for a wide range of applications e.g. for buried and open pipelines, process piping offshore, subsca pipelines and flowlincs, applications in the nuclear power industry and in materials research in general. This paper describes typical applications of the FSM technology, and presents operational experience from some of the landbascd and subsca installations. The paper also describes recent enhancements in the FSM technology and in the analysis of FSM readings, allowing for monitoring and detailed quantification of pitting and mesa corrosion, and of corrosion in welds.