Yacht Corrosion
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===Background=== | ===Background=== | ||
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Simply enough, if you mix different metals and add salt water, you will get corrosion. That's a fundamental law of physics. It's also a fact of life that boats live in salt water, and often contain many different metals. It's a wonder that some of them still float! | Simply enough, if you mix different metals and add salt water, you will get corrosion. That's a fundamental law of physics. It's also a fact of life that boats live in salt water, and often contain many different metals. It's a wonder that some of them still float! | ||
| - | + | ==Hull Corrosion== | |
====Steel Hulls==== | ====Steel Hulls==== | ||
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====Types of steel, stainless steel and other metals and alloys==== | ====Types of steel, stainless steel and other metals and alloys==== | ||
| - | + | ==Causes== | |
====Galvanic Corrosion==== | ====Galvanic Corrosion==== | ||
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====Stray Current Corrosion==== | ====Stray Current Corrosion==== | ||
| - | + | ==Avoidance== | |
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The methods to avoid corrosion include: | The methods to avoid corrosion include: | ||
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====Install Bonding Circuits==== | ====Install Bonding Circuits==== | ||
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"''Bonding'' is the practice of electrically tying together major metal objects on a boat (e.g. rigging and chainplates, engine and propeller shaft, stove, metal fuel and water tanks, fuel deck-fill fittings, metal cases on electrical equipment, etc.) and connecting them to the boat's ground." (Calder p212). | "''Bonding'' is the practice of electrically tying together major metal objects on a boat (e.g. rigging and chainplates, engine and propeller shaft, stove, metal fuel and water tanks, fuel deck-fill fittings, metal cases on electrical equipment, etc.) and connecting them to the boat's ground." (Calder p212). | ||
A good diagram of a bonding circuit is in Calder p212, with an electrical schematic on p213. Note that quite heavy wire gauges are used, typically 6AWG or so (for those more used to dealing with metric wire sizes an AWG to European standard wire gauge chart is on Calder p167). The idea being that the bonding circuit is a "husky, low resistance circuit with electrically tight connections" and that any stray currents that may cause galvanic corrosion will choose the path of electrically least resistance to ground, that is the bonding circuit rather than any metal fittings on the surface of the boat. | A good diagram of a bonding circuit is in Calder p212, with an electrical schematic on p213. Note that quite heavy wire gauges are used, typically 6AWG or so (for those more used to dealing with metric wire sizes an AWG to European standard wire gauge chart is on Calder p167). The idea being that the bonding circuit is a "husky, low resistance circuit with electrically tight connections" and that any stray currents that may cause galvanic corrosion will choose the path of electrically least resistance to ground, that is the bonding circuit rather than any metal fittings on the surface of the boat. | ||
| - | + | ==Testing== | |
====Silver/Silver Chloride Half Cell==== | ====Silver/Silver Chloride Half Cell==== | ||
| - | + | ==References== | |
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* Nigel Calder, Boatowner's Mechanical and Electrical Manual: How To Maintain, Repair, and Improve Your Boat's Essential Systems — 3rd Edition. | * Nigel Calder, Boatowner's Mechanical and Electrical Manual: How To Maintain, Repair, and Improve Your Boat's Essential Systems — 3rd Edition. | ||
| - | * Miner K. Brotherton, The 12-Volt Bible for Boats — 2nd Edition | + | * Miner K. Brotherton, The 12-Volt Bible for Boats — 2nd Edition |
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===Forum Discussion Topics=== | ===Forum Discussion Topics=== | ||
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Links to discussion threads on the CruiserLog forum: | Links to discussion threads on the CruiserLog forum: | ||
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* [http://www.cruiserlog.com/forums/index.php?showtopic=8745 Corrosion on yachts] | * [http://www.cruiserlog.com/forums/index.php?showtopic=8745 Corrosion on yachts] | ||
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===Links=== | ===Links=== | ||
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* [http://www.kastenmarine.com/mbqCref.pdf Corrosion, zincs and bonding] - An excellent article (pdf). | * [http://www.kastenmarine.com/mbqCref.pdf Corrosion, zincs and bonding] - An excellent article (pdf). | ||
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| + | ==Also See== | ||
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Revision as of 11:43, 4 March 2009
Contents |
Corrosion on Yachts
Background
Simply enough, if you mix different metals and add salt water, you will get corrosion. That's a fundamental law of physics. It's also a fact of life that boats live in salt water, and often contain many different metals. It's a wonder that some of them still float!
Hull Corrosion
Steel Hulls
Metal Parts underwater
Types of steel, stainless steel and other metals and alloys
Causes
Galvanic Corrosion
Stray Current Corrosion
Avoidance
The methods to avoid corrosion include:
Cathodic Protection (Zinc)
Install Bonding Circuits
"Bonding is the practice of electrically tying together major metal objects on a boat (e.g. rigging and chainplates, engine and propeller shaft, stove, metal fuel and water tanks, fuel deck-fill fittings, metal cases on electrical equipment, etc.) and connecting them to the boat's ground." (Calder p212).
A good diagram of a bonding circuit is in Calder p212, with an electrical schematic on p213. Note that quite heavy wire gauges are used, typically 6AWG or so (for those more used to dealing with metric wire sizes an AWG to European standard wire gauge chart is on Calder p167). The idea being that the bonding circuit is a "husky, low resistance circuit with electrically tight connections" and that any stray currents that may cause galvanic corrosion will choose the path of electrically least resistance to ground, that is the bonding circuit rather than any metal fittings on the surface of the boat.
Testing
Silver/Silver Chloride Half Cell
References
- Nigel Calder, Boatowner's Mechanical and Electrical Manual: How To Maintain, Repair, and Improve Your Boat's Essential Systems — 3rd Edition.
- Miner K. Brotherton, The 12-Volt Bible for Boats — 2nd Edition
Forum Discussion Topics
Links to discussion threads on the CruiserLog forum:
Links
- Corrosion, zincs and bonding - An excellent article (pdf).
Also See
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