CATHODIC PROTECTION SYSTEMS WITH SACRIFICIAL ANODES: 5 IMPORTANT KEY POINTS TO CONSIDER
How important are cathodic protection systems? What role does the purity of anode material play in galvanic corrosion? How often should anodes be replaced for better hull protection against corrosion?
If you seek to receive solid answers to those questions, and discover reasons why your current cathodic protection isn’t working as it should, this article covers both your inquiries. Let’s dive deeper into those questions, and elaborate on the factors affecting cathodic protection of ship hulls.
- Ship corrosion and related factors
- Metal nobility versus metal reactivity
- What is cathodic protection?
- How does cathodic protection work?
- Sacrificial anode cathodic protection systems – 5 key factors to consider
SHIP CORROSION AND RELATED FACTORS
Corrosion is a natural occurring process by which metals turn into rust when exposed to oxygen. Statistics show that 90% of ship failures are attributed to corrosion. This translates into major-league financial figures, when we actually understand that the total losses from marine transport corrosion ship damage is 3% of the world’s GDP!
The factors that relate to ship corrosion are:
- Environmental conditions (salinity, contamination, acidic/alkaline environment etc)
- Material that undergoes corrosion (metal nobility and reactivity)
- Morphology of the corrosion attack
- Corrosion with oxygen or hydrogen
- Mechanical stresses of the system
METAL NOBILITY VERSUS METAL REACTIVITY
The strictest definition for noble metals refers to the filled electron d-band of the metal, and it’s more of a definition used by chemists. An easier to understand definition claims that a noble metal is one which resists oxidation and corrosion, like platinum, gold and silver. In the opposite direction stand the least noble and more active metals like Magnesium, Zinc and Aluminium.