Carbonic Acid Formation

Describes how carbon dioxide released from bicarbonate decomposition dissolves in condensate to form carbonic acid, dropping condensate pH to 4 or even 3 and corroding mild steel piping.

$$\mathrm{C}{\mathrm{O}}_2+{\mathrm{H}}_2\mathrm{O}\leftrightarrow {\mathrm{H}}_2\mathrm{C}{\mathrm{O}}_3$$

Variables

Symbol	Meaning	Unit
CO2	Carbon dioxide carried over with the steam	dimensionless
H2O	Water (condensate)	dimensionless
H2CO3	Carbonic acid	dimensionless

Worked example

In condensate systems with significant makeup alkalinity, resulting pH can drop to 4 or 3. At the Perfect Storm site, condensate pH fell from a controlled 8.5 to 5.9.

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Part of The Blueprint of Water