What are the undesirable deposits commonly found on steam turbine blading?

Sodium hydroxide and silica are indeed undesirable deposits that can accumulate on steam turbine blading. These materials can originate from chemical reactions occurring within the steam system, particularly when the water treatment process is compromised. Sodium hydroxide, a strong alkali, can lead to pitting and stress corrosion cracking when it deposits on the turbine blades. Silica, which may also enter the steam system through water or impurities, can form hard deposits that reduce thermal efficiency and contribute to erosion.

In steam turbines, it is crucial to have clean blading surfaces to maintain efficiency and longevity. Accumulation of these deposits can alter the surface properties of the blades, disrupting the smooth flow of steam and consequently leading to performance issues.

Other substances such as calcium carbonate and magnesium can contribute to scaling and are problematic; however, they are typically more associated with boiler systems rather than the specific concerns of turbine blading. Iron oxide may indicate corrosion but may not directly lead to the same types of performance degradation as sodium hydroxide and silica. Lead and sulfur compounds, while potentially harmful, are not commonly identified as the primary deposits affecting steam turbine blades in the same context. Therefore, sodium hydroxide and silica are particularly relevant to the turbine environment, making this choice the most accurate.