Preventive Tips Against Marine Electrolysis

Let’s exclude the technical aspects of marine electrolysis formation and concentrate on how it can be prevented. Of course it is important to understand this phenomenon, but our intention is provide the benchmarks that will assure success towards boat metal parts preservation.

Marine electrolysis can be avoided in most cases combining practical techniques, but most importantly through monitoring. Underwater monitoring and anode replacement is not enough; complementary external and internal boat inspections are essential to have all your bases covered.

To do so it is necessary to separate actions in both elements: “Marine Electrolysis Prevention above deck” and “Marine Electrolysis Prevention below deck.”

Marine electrolysis prevention tips – Above deck

Internal Bonding wire Make sure that bonded through-hulls, underwater lights, trim tabs and other boat parts remain properly connected and the wires are in good shape. Perform inspections carefully and regularly. Search for power cords in contact with the water around your boat and make sure to pull them out if so.

Meet your neighbors; find out if their boat metal parts are electrolysis-free and if they are well maintained vessels.

Using a Galvanic Isolator is a great way to isolate your vessel from others; blocking low voltage DC currents coming on board your boat through the shore power ground wire. Just make sure that the selected equipment meets the ABYC (American Boat & Yacht Council) specifications.

Marine electrolysis prevention tips – Below deck

electrolysis It is important to understand that different marinas, docks and slips create particular electrolysis environments and boat metal parts are affected differently. It is almost impossible to establish a pattern when measuring marine electrolysis. Each case should be taken on an individual basis.

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 must be brushed during the hull cleaning visit to determine how much zinc life is left.

The contact between metals (zinc/boat metal part) must be spotlessly clean.

Maintain original manufacturer zinc configuration, do not overload the 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 environment.”

It is fairly difficult to glance at a failed metal boat part and tell immediately what caused that particular failure. Most likely the failure was caused by a combination of reasons, including wrong choice of alloy by the manufacturer, manufacturing error, such as overheating, contamination or wrong coating, error in application by the boat builder, water velocity, impurities, or pollution in the electrolyte (sea water), temperature, vibration, stress, crevice, galvanic or stray current corrosion.

Galvanic Corrosion:

A natural phenomenon is that two different connected metals immersed in sea water, or electrolyte, develop voltage and current. The metal that is most active electrically (more positive) will deteriorate while protecting the metal that is less positive. If both of these metals are important to us, we can attach another metal, more positive than the other two, which will deteriorate first and protect the more important metals. This sacrificial metal will erode, protecting the boat metal that is bonded to it and exposed to the same body of water.

Stray Current Corrosion (commonly called Electrolysis):

Stray current corrosion is similar to Galvanic Corrosion except that the voltage and current flow is created by an outside electrical source rather than spontaneously in nature, normally with much more force than galvanic action and can deteriorate our valuable boat metal in a very short period of time.

Mechanical Corrosion:

Turbulent water, high velocity water (especially at bends in cooler tubing), and silt laden water will all cause erosion of metals. Uneven velocity inside a tube or across metal surfaces of boats in tidal water or drifting will also cause erosion. Propellers have several special problems, in that they have large uneven surfaces exposed to tidal currents which causes temperature and electrical differences on different areas of surface, and also differences in voltage due to the different speed between the hub and blades. Besides balancing the shaft and propellers, bonding, using shaft straps and an anode system will normally keep propeller erosion to a minimum by evening out the voltage over the entire propeller surface.



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