Effects of Hydrogen on Electrochemical Behavior of Nickel and Alloy 690 in Weak Alkaline Solution

The effects of pre-charged hydrogen on electrochemical behavior of Alloy 690 in a slightly alkaline solution at 25,50 and 70 ℃ were investigated by electrochemical methods. The results showed that pre-charged hydrogen shifted the open circuit potential in the negative direction,decreased the electrochemical impedance,did not affect the shape of the anodic polarization curve,increased the current density in the anodic polarization curve at potentials before the first transpassivation potential for alloy 690 in a bicarbonate solution. Pre-charged hydrogen caused a new current peak,increased the current density at potentials before the transpassivation potential for nickel,and decreased the electrochemical impedance for alloy 690 in a bicarbonate solution. The effects of hydrogen on electrochemical behavior of metals or alloys were related to the types of electrode reactions,the rate-determining steps and the stability of surface films.