Exam Question

### (a) Effects of Taking Fresh Water from Shore for Auxiliary Boilers
Using untreated fresh water from shore as feedwater for an auxiliary boiler can have severe detrimental effects on the boiler's integrity and operational efficiency. The primary issues stem from dissolved gases, dissolved mineral salts (hardness), suspended solids, and incorrect pH.
1. **Corrosion due to Low pH (Acidity)**:
* **Mechanism**: Shore water can be neutral or slightly acidic (pH < 7). Boiler water must be maintained in an alkaline state (pH 9.5 - 10.5) to form and maintain a protective, passive layer of magnetite (Fe₃O₄) on the internal steel surfaces. If the pH is low, this protective layer dissolves, exposing the parent metal to direct acid attack.