Which substance would provide good scale prevention in an open cooling system?

Which substance would provide good scale prevention in an open cooling system?

• A. Calcium carbonate
• B. Sodium bicarbonate
• C. A sulfuric acid chromate solution
• D. Pure water

Answer: (C)

In open cooling systems, scale forms when minerals like calcium carbonate precipitate out of the water onto heat transfer surfaces. This happens more easily when the water is alkaline and carbonate hardness is high. Keeping calcium in solution by lowering the water’s pH prevents that precipitation, since acidic conditions shift the carbonate balance toward dissolved forms rather than solid CaCO3. The sulfuric acid in a sulfuric acid chromate solution lowers pH to reduce scale formation, while the chromate provides corrosion protection for metal surfaces, which helps overall system reliability. The other options either introduce scale-forming compounds (calcium carbonate), raise alkalinity (sodium bicarbonate), or offer no chemical scale control (pure water). So this option best prevents scale in an open cooling system.

In open cooling systems, scale forms when minerals like calcium carbonate precipitate out of the water onto heat transfer surfaces. This happens more easily when the water is alkaline and carbonate hardness is high. Keeping calcium in solution by lowering the water’s pH prevents that precipitation, since acidic conditions shift the carbonate balance toward dissolved forms rather than solid CaCO3. The sulfuric acid in a sulfuric acid chromate solution lowers pH to reduce scale formation, while the chromate provides corrosion protection for metal surfaces, which helps overall system reliability. The other options either introduce scale-forming compounds (calcium carbonate), raise alkalinity (sodium bicarbonate), or offer no chemical scale control (pure water). So this option best prevents scale in an open cooling system.