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Showing posts from September, 2017

Boiler Corrosion

Galvanic Corrosion Can occur due to Oxygen attack or contact of two dissimilar metals in an electrolyte (eg: Copper + Steel). Oxygen Attack (Pitting Corrosion) At the Anode: Metal goes into solution               Fe ⟶ Fe 2+ + 2 e -               OXIDATION At the Cathode: Oxygen is reduced           ½ O 2 + H 2 O + 2 e - ⟶ 2 OH -             REDUCTION The variables pH, temperature and the concentration of oxygen affect the rate of corrosion. To avoid this alkaline conditions are maintained in the boiler. Oxygen reacts with iron to give ferric oxide (rust) Fe 2 O 3 which will not protect the metal from further attack and metal is continuously dissolved. 4Fe + 3O 2 → 2 Fe 2 O 3 Hematite (ferric oxide) Oxygen corrosion is usually observed as localized pitting on a metal surface. (Pitting Corrosion) This form of corrosion can be reduced by: 1.by reducing the level of oxygen as far as possible using mechanical means which include deaeration and/or judi

Boiler Scale Formation