Impact of coupling to carbon steel on hydrogen uptake and cracking of duplex stainless steel in oilfield environments

The effect on 22 Cr duplex stainless steel of coupling to carbon-steel in acid brine environments at 80 degrees C has been evaluated. At low charging currents, hydrogen uptake was independent of pH and H2S and proportional to the square root of the charging current density, i(1/2). At higher charging currents, a critical value was reached above which hydrogen uptake was independent of the charging current density in H2S-free solution. In H2S environments, hydrogen uptake remained proportional to i(1/2) and independent of the concentration of H2S. No significant reduction in the strain-to-failure relative to oil was observed in H2S-free environments. Pre-exposure for 50 days had only a modest effect on the strain-to-failure. In H2S environments, cracking may occur at coupling currents greater than 100 mu A cm(-2).