Electrochemical Hydrogen Permeation Studies of Several Mono- and Diamines

An electrochemical hydrogen permeation measurement system was designed, constructed, and successfully used. The diffusion coefficients for the permeation of hydrogen atoms through steel estimated in this study using the time-lag and Laplace methods are of the same order of magnitude as those in the published literature. In several hydrogen permeation curves, a characteristic hump was observed. We propose that this hump is due to the trapping of hydrogen at sites other than voids and microvoids. The electrochemical system was also used to study the effectiveness of diethanolamine (DEA), morpholine (MOR), triethanolamine (TEA), ethylenediamine (EDA), and hexamethylene diamine (HMDA) in inhibiting the entry of hydrogen atoms into steel. The diamines were found to be more effective than the monoamines. A nonlinear relationship was observed between the inhibition effectiveness and the concentration of the amines studied. The inhibiting abilities of the monoamines were similar at the high concentration limit (0.01M) but followed the trend TEA > MOR > DEA at the low concentration limit (5 X 10^-5M). For the diamines the inhibiting abilities were also similar at the high concentration limit (5 X 10^-3M) and followed the trend HMDA > EDA at the low concentration limit (5 X ^10-5M).