Tip of the Month
July, 2010 - Anodes
"What on earth are anodes", I hear you say. Well you probably first came across 'anodes' in the school chemistry lab! Actually, they are properly called sacrificial anodes.
Different metals immersed in water will suffer errosion as electrons migrate. The zinc sacrificial anode used in seawater, being less electronegative than the metals used for props, shafts, rudders etc. will errode and protect the running gear of your vessel. Boats kept in fresh water usually use magnesium sacrificial anodes alone, but if they regularly go out into salt water then they will need to have zinc anodes as well.
Once the anodes have been completely eroded, the rest of the underwater metals on your boat will start to erode. As you might imagine this can get costly. I recently bought a yacht that had not been properly protected and after a brief initial inspection I thought I might have to replace the prop. As it turns out, there was enough life left in the blades for a quick brush up in the hands of an expert and it's now back on the end of the prop shaft working as it should.
My advice to you is, for the first few months you own your new boat, to regularly check your anodes and indeed the wiring on the inside of your boat that connects the anodes to the various bits of machinery that come into contact with the water. You may also find that there are plugs screwed into your engine block that will need replacing as they erode. Having regularly checked the erosion rate of your anodes you will be able to schedule less frequent checks. Depending on where you keep your boat, you might need to replace your anodes once a year or in the worst case, I heard, every six weeks!
richard.corbett@sealine.com
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