4 Barrier Corrosion logging is designed to evaluate the remaining metal thickness of the well completion elements such as tubing and/or casing, up to 4 barriers, based on emission and receipt of an electromagnetic field with the following computation of data in software. Fully autonomous Corrosion logging tool requires no preparation of well completion such as a scraper run. It is a stand-alone survey aimed to save time and cost for the mature wells integrity evaluation.