Exam Question
Explain how external hull corrosion is inhibited by EACH of the following:
(a) Cathodic protection (6)
(b) Impressed current system (6)
(c) Design and maintenance (4)
Class 4 (4th Engineer)
SC&S
📅 Dec 2022
Reference Answer
### (a) Cathodic Protection (Sacrificial Anode System) (6 Marks)
Cathodic protection is an electrochemical method of corrosion control that makes the entire metallic surface of a ship's hull act as the cathode of an electrochemical cell, thereby preventing it from corroding.
**1. Electrochemical Principle:**
Corrosion is an electrochemical process that requires four components: an anode (where oxidation occurs), a cathode (where reduction occurs), a metallic path (for electron flow), and an electrolyte (e.g., seawater). On a steel hull, microscopic differences in composition and stress create anodic and cathodic sites, leading to the formation of small corrosion cells where the anodic sites corrode.
Cathodic protection is an electrochemical method of corrosion control that makes the entire metallic surface of a ship's hull act as the cathode of an electrochemical cell, thereby preventing it from corroding.
**1. Electrochemical Principle:**
Corrosion is an electrochemical process that requires four components: an anode (where oxidation occurs), a cathode (where reduction occurs), a metallic path (for electron flow), and an electrolyte (e.g., seawater). On a steel hull, microscopic differences in composition and stress create anodic and cathodic sites, leading to the formation of small corrosion cells where the anodic sites corrode.
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