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Old 06-18-2007
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How important is it to change zincs in fresh water?

In another thread I just learned that, when in fresh water, you need to replace your zinc sacrificial anodes with magnesium. Since I kind of hijacked that thread I figured I would start a new one. Our boat entered fresh water Mid-May and will be hauled in October (so figure 5 1/2 months in fresh water) and we'll probably be bringing her back to salt water next year.

Is it worth the expense of hauling her to replace the zincs? Will they "coat themselves" with zinc oxide so quickly that they are useless? I'm concerned that I'll have to haul her twice - first to measure the prop shaft zinc and the hull plate zinc - and second to actually replace them once I find ones that fit. Even hauling her once is a few hundred $$$'s.

I'm assuming that what will happen is that they will become coated with zinc oxide, becoming useless for their purpose, which will allow other metals to give up their electrons faster than the zinc? Is galvanic corrosion still a risk in fresh water?

If I need to do it, I need to do it...

Thanks!
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