🔍 Key Concepts

• Hard scale vs soft sludge in boiler water treatment • Role of phosphate treatment in reacting with calcium and magnesium hardness • Effect of pH (acidic vs alkaline) on scale formation and corrosion

💭 Think About

• Which treatment chemical in the options is specifically used to react with calcium to form a soft, removable precipitate rather than a hard scale on metal surfaces? • How does slightly acidic boiler water affect metal surfaces and scale formation—does it help prevent or actually promote corrosion and pitting? • Is high boiler water hardness something operators usually want to increase, or something they try to remove or chemically condition?

✅ Before You Answer

• Verify which option directly addresses calcium hardness control (not oxygen control, not general corrosion control). • Check which condition promotes a soft, non-adherent precipitate that can be blown down, instead of a tightly adhering hard scale. • Eliminate any choices that would clearly increase corrosion risk or are opposite to standard boiler water treatment practice.