What chemical is used to raise the pH of water to reduce its corrosive action?

Sodium hydroxide (NaOH) is commonly used to raise the pH of water in order to reduce its corrosive action. By increasing the pH, sodium hydroxide helps to make the water less aggressive towards metal surfaces and piping, which can be important in various water treatment processes and systems. When the water's pH is low, it can become corrosive, leaching metals and other impurities into the water supply, which can lead to contamination and infrastructure damage.

In contrast, while both sodium bicarbonate and calcium hydroxide can influence water chemistry, sodium hydroxide is particularly effective for significant pH adjustments. Ammonium sulfate, on the other hand, is primarily used as a fertilizer and does not serve the purpose of raising pH in the context of reducing corrosion. Hence, sodium hydroxide stands out as the most appropriate chemical for this specific application.