What is the best chemical to use for corrosion inhibition in water that is low in alkalinity and calcium concentration?

• A. Sodium bicarbonate
• B. Polyphosphates
• C. Sodium carbonate
• D. Chlorine

Answer: (B)

Polyphosphates are effective in corrosion inhibition, particularly in water that is low in alkalinity and calcium concentration. They work by forming a protective film on the metal surfaces within the water system, which helps to prevent corrosion. This film acts as a barrier against corrosive agents present in the water, effectively reducing the rate of corrosion that can occur in low alkalinity environments.

In cases where water has low calcium concentrations, polyphosphates are beneficial because they help maintain the stability of the water chemistry and can prevent the leaching of metals from pipes and fittings into the water system. They also aid in the reduction of scale formation while enhancing the overall quality of the water.

Other options such as sodium bicarbonate and sodium carbonate primarily serve to increase alkalinity or pH levels rather than directly inhibiting corrosion. Chlorine is used primarily for disinfection rather than corrosion control and can sometimes exacerbate corrosion issues in certain water systems. Hence, polyphosphates are the most suitable chemical choice for corrosion inhibition under the specified conditions.