Problem 13.1: At 140F feedwater contains roughly 4 mgL

From Chapter 13 Problem Set. Level 1: Conceptual Mastery.

Question

At 140°F, feedwater contains roughly 4 mg/L dissolved oxygen - half of what it held at room temperature. Explain why corrosion risk is higher at 140°F, not lower.

Answer

Show answer

Corrosion rates double every 18°F. At 140°F (~70°F above ambient) ≈ 3.9 doublings → ~23.9 ≈ 15×. Although half the oxygen is gone, the remaining 4 mg/L is reacting 15× faster. Net corrosion potential is approximately 7.5x compared to room temperature. The paradox does not resolve until the boiling point eliminates oxygen almost entirely.