Abstract: A method of measuring the rate of corrosion of a metallic structure that is subjected to a corrosive ambience. It subjects a thin metallic enclosure to the same ambience as the metallic structure is subjected to. The thin enclosure is subjected to the ambience on one side, while it maintains a different condition on the other side of the enclosure. Then, it detects a change when the different condition is no longer maintained due to the thin enclosure having corroded through.A probe for detecting the corrosion rate of metallic piping or the like. It includes a thin metal enclosure mounted with one side subjected to the corrosive ambience acting upon the piping. There is means for subjecting the other side of the thin enclosure to a condition that is different from that of the corrosive ambience. And, there is a means for detecting a change of the different condition when the thin metal enclosure corrodes through.