🔍 Key Concepts

• Boiler water chemistry and how impurities affect metal surfaces • The role of dissolved gases in causing pitting and overall corrosion • Difference between inert gases, basic ions, and gases that form acids in water

💭 Think About

• Which substance, when dissolved in water, is most likely to form an acid that attacks metal surfaces? • Look at each choice and ask: does this typically make the water more corrosive or more protective to steel? • Which options are gases that are generally inert in water, and which one is known in boiler treatment to be a specific corrosion concern along with oxygen?

✅ Before You Answer

• Identify which option is commonly discussed in boiler water treatment manuals as a corrosive gas, not just any gas • Eliminate any substances that are generally chemically inert with respect to water in this context • Consider whether hydroxyl ions (OH⁻) are associated with alkalinity (protective) or acidity (corrosive) in boiler water chemistry