CORROSION AND HYDROGEN SURFACE EMBRITTLEMENT INHIBITION OF AMORPHOUS FEBSIC ALLOY IN MOLAR HCI BY DIORTHOAMINODIPHENYLDISULPHANE (DOAPD)

The mode of corrosion inhibition of amorphous alloys due to diorthoaminodiphenyldisulphane (DOAPD) in molar HCl is studied through solution analysis and electrochemical steady state and transient measurements. DOAPD acts on the cathodic reaction without changing the mechanism of the hydrogen reduction reaction on the surface of the amorphous alloy electrode. The efficiency of corrosion inhibition depends on both the concentration of DOAPD and the potential of the electrode. The addition of 10(-4) M DOAPD to 1 M HCl increases the impedance and decreases the capacity of the double layer. From the comparison of results with those obtained using other organic compounds, it is shown that DOAPD is the best inhibitor. A correlation between the efficiency of corrosion inhibition of DOAPD and its molecular structure is established. A schematic representation of the surface coverage due to different action modes of DOAPD cations is presented. Evidence is revealed for a double role of DOAPD in the decrease of corrosion and in hydrogen penetration. The schematic representation proposed explains why the mechanism of hydrogen reduction reaction is the same in the absence and in the presence of DOAPD.