🔍 Key Concepts

• High-temperature corrosion in exhaust valves when burning residual fuel oils • The role of metallic salts (especially from seawater contamination) in forming corrosive compounds • Which elements in fuel are known to form low-melting-point ash deposits on hot engine parts

💭 Think About

• Think about which element is commonly paired with sodium and sulfur in discussions of residual fuel corrosion in marine diesel engines. • Ask yourself: which option is famous for forming high-temperature corrosive ash deposits on exhaust valves and turbocharger blades? • Which of the listed choices is typically monitored and limited in heavy fuel specifications because of its corrosive effect at turbine/exhaust temperatures?

✅ Before You Answer

• Check which element is often mentioned together as sodium–sulfur–[?] compounds in engine manufacturer manuals. • Eliminate options that are basic fuel constituents rather than trace metallic contaminants. • Verify which substance is known for forming low-melting-point, sticky ash that attacks exhaust valves at high temperature.