Explain hot and cold corrosion in marine diesel engines?

flowchart TD
    A[Fuel contaminants] -->|Na, V, S, H₂O| B[Hot corrosion]
    A -->|Sulphur| C[SO₂ formation]
    C --> D[H₂SO₄ formation]
    D -->|Condenses below dew point| E[Cold corrosion]
    B --> F[Exhaust valves, turbocharger]
    E --> G[Cylinder liners]

• Hot corrosion: high-temperature chemical attack in exhaust system from sodium, vanadium, water and sulphur in fuel
• Cold corrosion: sulphuric acid from fuel sulphur condenses at dew point on cylinder liners
• Hot corrosion prevention: low vanadium/sodium fuel or additives
• Cold corrosion prevention: high TBN cylinder oil and jacket temperature above acid dew point
• Officer action: monitor fuel quality, maintain temperatures, inspect components, record in PMS