Let’s leave aside the technical aspects of marine electrolysis formation and focus on how it can be prevented. Of course it is important to understand this phenomenon, but our intention is to provide the benchmarks that will ensure success in the conservation of the metal parts of ships.
Marine electrolysis can be avoided in most cases by combining practical techniques, but more importantly through monitoring. Subsea monitoring and anode replacement are not enough; Complimentary external and internal boat inspections are essential to get all your bases covered.
For this, it is necessary to separate actions in both elements: “Prevention of Marine Electrolysis on deck” and “Prevention of Marine Electrolysis below deck”.
Marine Electrolysis Prevention Tips – Above Deck
Internal Bonding Cable Make sure thru-hulls, underwater lights, trim tabs, and other bonded boat parts remain properly connected and cables are in good condition. Carry out inspections carefully and regularly. Look for power cables in contact with water around your boat and be sure to remove them if they are.
Get to know your neighbors; find out if the metal parts of your boats are free of electrolysis and if they are well maintained boats.
Using a galvanic isolator is a great way to isolate your boat from others; blocking low voltage DC currents from entering aboard your boat through the grounding wire from the grounding outlet. Just make sure the equipment you select meets ABYC (American Boat & Yacht Council) specifications.
Marine Electrolysis Prevention Tips: Below Deck
electrolysis It is important to understand that different marinas, docks and berths create unique electrolysis environments and metal parts on boats are affected differently. It is almost impossible to establish a pattern when measuring marine electrolysis. Each case must be taken individually.
Underwater zinc monitoring is king when it comes to electrolysis prevention.
Zinc monitoring involves a meticulous evaluation of each zinc: mass, installation and electrolysis reaction.
It is recommended to replace zincs at 50%.
Zincs should be brushed off during the hull cleaning visit to determine how much zinc life remains.
The metal-to-metal contact (zinc/metal part of the boat) must be impeccably clean.
Maintain original manufacturer zinc setting, do not overload system.
Make sure your diver understands the basics of the process.
Technical aspects of Corrosion:
“The destruction of a metal or alloy by chemical or electrochemical reaction with its surroundings.”
It is quite difficult to take a look at a failed metal part of a ship and immediately tell what caused that particular failure. The failure was most likely caused by a combination of reasons, including the manufacturer’s incorrect choice of alloy, manufacturing error such as overheating, contamination or incorrect coating, application error by the builder of the vessel, water velocity, impurities or contamination in the electrolyte (sea water), temperature, vibration, stress, cracks, galvanic or stray current corrosion.
Galvanic corrosion:
A natural phenomenon is that two different metals immersed in connected seawater, or electrolytes, develop voltage and current. Metal that is more electrically active (more positive) will deteriorate while protecting metal that is less positive. If both metals are important to us, we can add another metal, more positive than the other two, which will deteriorate first and protect the more important metals. This sacrificial metal will erode away, protecting the metal of the boat that is attached to it and exposed to the same body of water.
Eddy current corrosion (commonly called electrolysis):
Eddy current corrosion is similar to galvanic corrosion, except that the voltage and current flow are created by an external electrical source and not spontaneously, usually with much greater force than galvanic action, and can deteriorate valuable metal. our boat in a very short period of time. .
Mechanical Corrosion:
Turbulent water, high velocity water (especially around cooler pipe bends), and sediment laden water will cause metal erosion. Uneven velocity within a pipe or across metal surfaces of ships in tidal or drifting water will also cause erosion. Propellers have several special problems, as they have large uneven surfaces exposed to tidal currents causing electrical and temperature differences in different areas of the surface, and also voltage differences due to the different speed between the hub and the blades. In addition to balancing the shaft and propellers, bonding, the use of shaft straps and an anode system will normally keep propeller erosion to a minimum by leveling the voltage across the propeller surface.
