🔍 Key Concepts

• Effects of moisture on metal surfaces over long idle periods • Difference between short-term shutdown and extended lay-up of boilers • What water washing leaves behind on the fireside surfaces

💭 Think About

• Ask yourself what happens to bare metal when it stays damp and exposed to air for weeks or months • Consider which of the choices describes a long-term effect rather than something that happens only at lighting off • Think about how moisture in soot, scale, and deposits affects the boiler internals over time

✅ Before You Answer

• Identify which option deals with long-term surface damage rather than immediate operating problems • Decide which answer is most directly linked to moisture left on the fireside after washing • Eliminate any choices that mainly relate to rapid heating or combustion at start-up, not to storage conditions