The electrochemical measurement of the permeation r·ate of hydrogen through metal foils consists of charging of the metal with hydrogen on one side of the foil and removal of hydrogen by electrochemical oxidation on the other side. The hydrogen diffusion coefficient can be determined by mathematical analysis of the time dependence of the oxidation current. This electrochemical technique can also be used to determine the hydrogen concentration in metals. For this purpose, an electrochemical cell is placed on the metal to be analyzed and a hydrogen concentration gradient is produced by oxidation of all hydrogen atoms which reach the surface. Under a contract with the Naval Air Development Center a portable "barnacle cell" system - so-called because of its magnetic attachment to steel surfaces - is developed for field use such as determination of hydrogen concentration in aircraft landing gears. The system consists of two parts: the measuring cell in a cylindrical magnet (1.5 inch diameter) and the electronic system which allows recording of the permeation current-time trace and integration of this trace over pre-set time intervals.