All boats from commercial fishing vessels to luxury yachts face a constant threat from corrosion. Among the various types of corrosion, galvanic corrosion is particularly notorious for its ability to quickly eat away at metal components, causing significant damage and costly repairs.
Galvanic corrosion isn't something you really need to know about if you're living on land, but if your life is sea bound it becomes much more important. To help out, we're going to delve into the basics of galvanic corrosion on boats, exploring some of the causes, effects, and most importantly, how to prevent it.
What is galvanic corrosion?
Galvanic corrosion occurs when two dissimilar metals come into contact and are exposed to an electrolyte, such as salt water. One metal acts as an anode, meaning it corrodes, while the other acts as a cathode, remaining protected. The flow of electrons from the anode to the cathode through the electrolyte is what leads to the deterioration of the anodic metal.
It's a common type of corrosion in marine environments and is something to understand if you want to prevent damage to your boat or liveaboard yacht.
Causes of galvanic corrosion on boats
Here are two of the main causes of galvanic corrosion on ocean-going vessels.
Dissimilar metals coming in contact
Boats are composed of various metals like aluminium, stainless steel, bronze, and zinc, and often these metals touch. When two metals that aren't the same come into contact in a conductive environment, like saltwater, galvanic corrosion can occur.
On a sailboat the most common cause of galvanic corrosion we've seen is when stainless steel comes into contact with aluminium. Here's some places you might find galvanic corrosion around your boat.
Stainless steel fixings being used to hold aluminium framed solar panels
Aluminium rivets or fixings into a stainless steel frame or solar arch
Stainless steel rivets, bolts or mounts on an aluminium mast
Stainless steel fittings contacting an aluminium hull
Stainless steel bolts used to hold aluminium trampoline buttons on catamarans
Stray electrical current
Electrical systems onboard, such as shore power connections or improperly installed wiring, can inadvertently create galvanic cells which accelerates corrosion. If you were to have a stray current aboard your boat, you may notice the aluminium anodes below the waterline are corroding much faster than expected. This is because the electrical current is acerbating the corrosive reaction of the anode immersed in salt water.
The negative impact of galvanic corrosion
Galvanic corrosion can have severe repercussions for boat owners if left unresolved.
Irreparable damage to critical components like the hulls, props, hatches, through-hulls and mast, which can impact the structural integrity of the vessel
Corrosion on the props and shafts can lead to decreased speed and manoeuvrability, impacting the boat's performance and fuel efficiency
Expensive repair or replacement bills for parts that have corroded, including anodes, hatches, solar panels and structural components like the mast
How to prevent galvanic corrosion
Unfortunately the only ways to fix galvanic corrosion on yachts and boats is to prevent it from happening in the first place. Here are a few ways you can prevent galvanic corrosion aboard your power boat or sailing yacht.
Use sacrificial anodes where appropriate and make sure they are changed as needed
Install galvanic isolators in the electrical system where advised
When you first get the vessel or are installing new components, analyse the potential for galvanic corrosion and put things in place to mitigate the damage from the start
Apply a galvanic corrosion inhibitor such as Duralac or Tef-Gel where appropriate
Monitor the electrical system for electrical leaks or faults that could lead to galvanic corrosion as a consequence of the stray voltage
Summing it up
Galvanic corrosion poses a significant threat to the longevity and performance of boats, but with proper understanding and preventive measures, its impact can be mitigated. Its best that boat owners remain proactive in implementing corrosion control strategies to safeguard their vessels and prevent issues before they become a problem.
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