Results were presented from a four-year experimental study on carbon d
ioxide (CO2) corrosion of carbon (C) steel in two-phase flow. Tests we
re carried out in a gas and water loop that permitted control and regu
lation of relevant parameters. Flow rates of gas and water were regula
ted independently to obtain a number of two-phase flow regimes, such a
s bubble flow and slug flow. In more than 20 long-term experiments las
ting from one to several weeks each, pH was varied from 4 to 7 while t
he temperature was held at 20 degrees C, 40 degrees C, 60 degrees C, a
nd 80 degrees C in different experiments. Corrosion rates were monitor
ed continuously in time with a radiation detection technique. Scanning
electron microscopy analysis and x-ray analysis of the specimen surfa
ce and cross section were done on selected specimens after each experi
ment. It was found that, in cases where the formation of protective fi
lms is difficult, flow could have a ''positive'' role by eroding the i
ron carbide films that otherwise would accelerate corrosion by galvani
c action. When protective films did form (higher pH and higher tempera
tures, Fe2+ at saturation or supersaturation), corrosion rates on the
order of 0.1 mm/y were obtained. In most cases, protective films prove
d very resistant to mechanical erosion even in severe flow caused by s
lugging and flow disturbances. In some cases, damage at the top of the
pipe was more extensive than at the bottom.