Effects of ethanolamine, ammonia, and acetic and formic acid on two-phase flow-accelerated corrosion were investigated in an experimental loop simulating the conditions found in a water-steam cycle. Results indicate that the effects of acetic acid and ethanolamine on the corrosion rate neutralize each other. The effect of acetic acid on the corrosion rate was most pronounced at the highest tested steam quality. A model simulation for liquid film pH at 90% steam quality suggests that at very high steam qualities the protection ethanolamine provides increases, while the protection provided by ammonia goes down. A linear relation between calculated liquid film pH and the measured corrosion rate was found for 24% steam quality within a pH range from 5.6 to 6.3. Formic acid was thermally unstable at the tested temperatures and had no effect on the corrosion rate.