Encyclopedia of practical advice on the mechanics and related sciences
The main points of steam boiler water treatment
The main causes of steam boiler parts corrosion are insoluble gases, incorrect pH level, chloride ions and mechanical contents.
Gases – oxygen, carbon dioxide, ammonia. Oxygen reacts with iron to form Fe2O3 ferric oxide. Carbon dioxide, when contacted with water, forms carbon acid, lowers the pH and oxidizes the metal. Ammonia is dangerous in the reaction with oxygen.
Hydrazine during the chemical treatment removes oxygen from the boiler water, forming water and nitrogen – which is inert.
Carboxylic acid neutralizes by the morphoxime (morpholip).
Sea water ingress into the boiler water carries with it salts or magnesium chloride forming ions of magnesium and chloride. Chloride ions react with hydrogen ions and lower the pH. Magnesium ions react with phosphates and hydroxide ions and form sediment. The sediment and other harmful deposits from the surface of the pipes are removed by boiler lower blow-down.
Acid corrosion is removed with alkaline solutions, such as sodium hydroxide, and is increased.