Class 1 (Chief Engineer) Engineering Management 📅 Jul 2021

Exam Question

With the introduction of the new generation of super-long stroke engines and changed process parameters triggered by environmental compliance rules, 'cold corrosion' of cylinder liners has grown to become a major issue for the latest generation of two-stroke engines. Discuss the causes and mitigation measures, stressing on the following:

(a) Increased jacket cooling water temperatures systems (b) New cylinder liner designs

Reference Answer

### **Introduction to Cold Corrosion**
Cold Corrosion is an aggressive form of corrosive wear affecting cylinder liners and piston rings in two-stroke marine diesel engines. It occurs when the liner surface temperature falls below the dew point of sulfuric acid present in the combustion gases. The introduction of super-long stroke engines, designed for higher efficiency and compliance with environmental regulations (EEDI, Tier III), has exacerbated this issue. These engines operate at lower RPMs and often engage in 'slow steaming', leading to lower combustion and component temperatures, which creates a favorable environment for acid condensation.
**Chemical Mechanism:**
1. **Sulphur Combustion**: Sulphur (S) present in the fuel oil oxidizes during combustion to form Sulphur Dioxide (SO₂).

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