anodes

[atlantic]

i have a pacific 32 work boat with twin hamilton jets.the boat is moored in brackish water and goes to sea through a lock. what type of anodes should i have on the transom and also the jets. i have been told a mixtur of zinc and aluminium anodes. is this correct ?

 

[umblecumbuz]

Re: anodes

Hi ILB,<br /><br />There's a faq on anodes (Dealing with corrosion ....), but it deals with principles only - not specifics.<br /><br />Anodes vary water to water, and can be almost any combination of sacrificial metals. Most accurate way is to visit the local chandler and see what they advise. They know the local conditions.<br /><br />Maybe someone out there is local to your area, but anyone advising without local knowledge is just shooting in the dark.

 

[bayman]

Re: anodes

I'd say you are on the right track atlantic, you want plenty of weak metals (anodes) to stop the stronger metals from corroding. You especially want them located near the metals likely to corrode, as you have also mentioned.<br /><br />What is the boat hull made of? If it is a steel work boat you will want to be generous with your placement of anodes.<br /><br />Along the lines of what stillfishing says, If you can, talk to people who have similar boats moored in the same area. See what they are using and how it has worked for them.<br /><br />Also, be aware that stray electical currents can cause very fast corrosion. These aren't usually very common but if they are present then they need to be dealt with soon.

 

[MH9371B]

Re: anodes

I was told by my mechanic to only use zinc, or only use aluminum. By using both, the aluminum will actually protect the zinc anodes from corroding, therefore you do not get the life out of the aluminum anodes that you should.

 

[umblecumbuz]

Re: anodes

Hi MH9371B,<br /><br />It's actually the other way around - the 'zinc' will normally get sacrificed before the aluminum. And that's a very good thing, because a lot of our boat parts are made of aluminum or an alloy of it.<br /><br />Most 'zincs' are not pure zinc, but a mixture of metals. Some contain magnesium, for example. That's why the advice to check local conditions was given.<br /><br />One browse through Westmarine's catalogue will show up a range of 'zincs' and give an idea of the kind of water they may be used in.<br /><br />If your zincs are not geting eaten away, that could be an indication that something more expensive is instead - like the unpainted inside of your outboard leg.<br /><br />Zinc or swim!

 

[bayman]

Re: anodes

I think what the mechanic meant who was talking to MH9371B is that the other weak metals (in addition to zinc) are a barrier against the entire anode corroding too quickly. Zinc is a very weak metal and corrodes very quickly. Therefore, other weak metals are added to anodes in case the Zinc corrodes quickly. That way there is still some protection left should things go unnoticed.

 

[umblecumbuz]

Re: anodes

Hi Bayman,<br /><br />Could be that's what the mechanic meant.<br /><br />Still, the whole purpose of a sacificial anode is that it gets sacrificed! This happens fast in clear, warm, moving water, and slowly in cold, still water.<br /><br />If your 'zinc' isn't corroding away, either it's the wrong mix of metals for the water you're in, or it's oxidised - that is, it has a furry whitish surface. The oxidation will slow down its purpose. The answer is to attack it with a file until you hit clean 'zinc'.<br /><br />You WANT it to slowly vanish. If it isn't, then some other metal on your boat is vanishing instead. Not good!<br /><br />Zincs are cheap insurance when you cost out a prop or an outboard leg corroding unseen from the inside!

 

[bayman]

Re: anodes

Yes, I agree with you stillfishing.