Carbonic Acid

Definition

The weak acid formed when carbon dioxide dissolves in condensate, driving condensate pH down to 4 or even 3. It is the chief corrosion threat in steam-condensate systems.

Carbon dioxide from bicarbonate decomposition condenses with the steam and reacts as CO2 + H2O reversibly forming H2CO3. In systems with significant makeup alkalinity the resulting pH can drop to 4 or 3, a devastating environment for the mild steel piping that makes up most condensate systems. Excess hydrogen ions attack the iron directly, cutting a characteristic groove at the bottom of the pipe where cool condensate pools.

Related concepts

Neutralizing Amines · Condensate Corrosion · Bicarbonate Decomposition

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Part of The Blueprint of Water · 🧪 chemistry