Practical experience related to boiler corrosion kinetics at different feedwater pH levels is included in Fig. 1.5. The kinetic information in Fig. 1.5 indicates that high oxygen contents are generally undesirable. It should also be noted from Figs. 1.5 and 1.6 that active corrosion is possible in acidified untreated boiler water, even in the absence of oxygen. Below the hydrogen evolution line, hydrogen evolution is thermodynamically favored as the cathodic half-cell reaction, as indicated.