🔍 Key Concepts

• Difference between hot corrosion and cold (low-temperature) corrosion in diesel engines • Role of fuel ash constituents such as vanadium and sodium in high‑temperature attack on exhaust valves and turbocharger components • Role of sulfur in fuel and formation of acidic condensate at low metal temperatures

💭 Think About

• Think about what happens to sulfur compounds in fuel when exhaust gas cools down and reaches dew point on cold metal surfaces—what type of corrosion is that? • Consider which fuel impurities create an aggressive ash deposit that attacks metal surfaces at very high temperatures, especially on exhaust valves and turbocharger blades. • Ask yourself: in practice, which problem do chief engineers worry about with high‑vanadium heavy fuel oils at high temperatures?

✅ Before You Answer

• Identify which constituent is primarily associated with high‑temperature (hot) corrosion of exhaust valves and turbine blades. • Identify which constituent leads to acidic condensate when exhaust gases cool below their dew point on cold surfaces. • Confirm that both hot and cold corrosion are linked to fuel chemical constituents, not just temperature control or heat distribution.