Boating Advice: Electrical bonding (Corrosion, Part 4)

If you are a boat owner or a potential boat owner you may want to read on. Insurance companies will not pay out or honour a claim if corrosion is present or if it is the cause of an incident or event.

For those that have followed Boating Advice series on Corrosion thus far (and many have made contact and I thank you for your loyalty), it’s time to get onto the bonding system.

This is the most important preventative maintenance program you can add to your list.

As a surveyor, I have invested time and money in education and with adding the right equipment to my toolbox. Every survey I carry out now has a diagnostic test on the system included.  

The results I have found have been amazing. Being able to have corrosion expert Brian Gatt from Logix Group supply a solution and rectification program has been invaluable. So let me share some advice to new boat buyers and even those selling their once loved liquid asset.

BONDING BASICS
- The name is Bond, cathodic and galvanic bonding
The basics of a bonding system is as follows: a wire run internally from your cathodic or galvanic protector i.e. anode, to all the metal fittings in the vessel i.e. shafts, stern and rudder glands/tubes, seacocks, etc.  

This wire links all the fittings, effectively applying a coating of the anode properties — e.g. Maddox/zinc/aluminium — over the metallic components that are required to obtain anodic protection, providing an all-important barrier against galvanic corrosion.

Many problems exist and many are related to the source, either under or over anode application and more importantly the wrong anode selection.

Yes there are options available on anode composition, they are not all zinc! (We will cover this in the next article).

Over time, the connections fail, every time you antifoul your vessel, there is every chance the connection is getting a higher amount of paint build up on the connecting thread, making it all but useless.

The wires become corroded themselves especially at terminal ends — remember current doesn’t flow through corroded metals very well. Some failures are actually due to the system being a daisy chain or linked, so one broken connection or one poor connection or one simple crushed wire can break the link. Break the link and we break the protection.

Even the positioning or water flow around the anode can affect the productivity of the bonding system.

TELLTALE SIGNS OF FAULTY BONDING
- Marine growth, inactive anodes, the halo effect
There are tell-tale signs that can be picked up at the time of slipping: high levels of growth on metal objects compared with the rest of the hull is one giveaway. More often than not a stray current is the cause or it's a result of 'over-anoding', which can destroy the copper component of the antifouling, making it about as useful as ‘Weathershield’ in stopping marine growth.

Another warning sign that bonding in ineffectual is when you have anodes that are not depleting or have a scale growth on them. These are totally inactive, indicating the system is down.

Another is paint that has blown off fittings or metal through-hull fittings. Leaving a halo effect around an anode or hull fitting can be a sign, too.

The best way to have these kinds of suspect things checked and identified is when the boat is in and out of the water, using the right equipment, and a professional...

After spending time with Brian and Jessica Gatt from Logix Group, I came away with an even better understanding on recommended testing procedures and the realities of some pretty poor bonding in our marine industry.

During the basic test, the output from the anode was at good levels, but as we tested further from the source the levels dropped and the exposure increased.  

We found the terminals had become old and connectivity was poor; we also found the shaft strap had broken a spring so we had a poor daisy chain or linked effect.  

This boat also lived on a mooring in an exposed area to wash. The anode placement was having a bearing on our results. As the boat lifted up and down, the range of readings was extremely varied.

Case 2: A 22ft production runabout. Originally berthed in the water fulltime, this boat was recently moved to a dry-storage facility. The boat was experiencing severe corrosion to the propeller and seacocks.

Testing was done as per normal using specialised equipment and straight away the result showed… no anodes were fitted! These vessels did originally have them, but they now seemed to have just vanished.

This boat had no bonding system to start with, but was a perfect example of why one is required and, importantly, the right system.

The fact this boat is dry stored  and living in dry storage half of its life also means it’s in the water the other half. With dry-stacking, you still need to perform scheduled maintenance including ensuring that your anodes and bonding works.

Note: Not all boats come standard with bonding systems. Installing bonding in timber vessels and yachts needs to be done on a case-by-case basis with an expert who can consider all facets on the boat including engineering.

8 BONDING STRATEGIES
- How to keep your boat’s bonding and anti-corrosion systems working.
1. For starters, it’s as simple as checking if your system is intact. Go from fitting to fitting and I’m sure you will find something has failed.
2.  Ensure the right quality of wire and connectors are used. A minimum of 6mm two-fine strand tinned wire is recommended.
3. Clean and proper connection points are a must. Also use protective coatings to prevent environmental corrosion.
4. Check the location of the anode; if it’s too close to the surface it mightn’t be working 24/7. There are many anodes that sit just below the waterline at full ship then, as we start using fuel and water or throw in highly exposed bouncy moorings, that exposed anode becomes inactive.
5. Prevention is better than cure. Test your system annually.
6. Check constantly the condition of all through hull fittings, gate valves, hose clamps, hoses and pipes for signs of corrosion or damage.    
7. If are having issues. employ an expert. The fee you believe is expensive for an expert diagnosis is actually a lot cheaper than a rejected insurance claim.
8. Completely upgrade your system every five years.

I hope you have enjoyed this discussion about bonding and, ultimately, our expert anti-corrosion strategies. Next we tackle anodes. This is very interesting, as there is a product out there that has turned the humble anode on its head, meaning better protection for you and your boat. Look for Corrosion Part 5, Anodes, next.

*Gavin Clark is a contributor at boatsales.com.au and BoatPoint.com.au who writes under the pseudonym 'The Surveyor'. He is a shipwright and marine surveyor with a business called Slipstream Marine based in Sydney. He has 27 years experience in the boating industry, is an avid boater and owner of a 33ft Sharpie (trawler). Gavin can be contacted at http://boatsurveying.com.au.