A stainless steel foil is explosively welded to the outside surface of a steel pipe. A capillary tube is welded to the foil, with a pinhole through the foil. As corrosion takes place on the inside of the steel pipe, free hydrogen is released by the corrosion process. The free atoms of hydrogen are small enough that they drift through the wall of the pipe. When they emerge from the outside of the pipe wall, they rapidly pair up to form H2 gas, which becomes entrapped between the foil and the pipe wall. The change in pressure under the foil is monitored to reveal the rate at which corrosion is occuring inside the pipe.

 

This method will not stop the corrosion, but it will provide useful information that can be used to more efficiently manage the application of corrosion inhibitors. Otherwise it would be difficult to know how effective current corrosion management practices might be. 

 

The most reliable way of attaching the foil is by means of explosive welding. Other methods, such as epoxy, are not leak proof, and can lead to inaccurate readings.