ELECTROCHEMICAL HYDROGEN PERMEATION STUDIES OF SEVERAL MONOAMINES ANDDIAMINES

An electrochemical hydrogen permeation measurement system was designed , constructed, and successfully used. The diffusion coefficients for t he permeation of hydrogen atoms through steel estimated in this study using the time-lag and Laplace methods are of the same order of magnit ude as those in the published literature. In several hydrogen permeati on curves, a characteristic hump was observed. We propose that this hu mp is due to the trapping of hydrogen at sites other than voids and mi crovoids. The electrochemical system was also used to study the effect iveness of diethanolamine (DEA), morpholine (MOR), triethanolamine (TE A), ethylenediamine (EDA), and hexamethylene diamine (HMDA) in inhibit ing the entry of hydrogen atoms into steel. The diamines were found to be more effective than the monoamines. A nonlinear relationship was o bserved between the inhibition effectiveness and the concentration of the amines studied. The inhibiting abilities of the monoamines were si milar at the high concentration limit (0.01M) but followed the trend T EA > MOR > DEA at the low concentration limit (5 x 10(-5)M). For the d iamines the inhibiting abilities were also similar at the high concent ration limit (5 x 10(-3)M) and followed the trend HMDA > EDA at the lo w concentration limit (5 x 10(-5)M).