sacrificial anodes?

[jeffo]

i have heard you can get sacrificial anodes for tinneys? is this true if so where can i get one from and where are they best positioned>? has any one got one on their boat? are they effective?
cheers. jeff

[TimNQ]

Alluminium doesnt rust much anyway jeff but you can try. However i have a feeling that zinc annodes and alluminium dont work to well together and it will start to decay the alluminium before the zinc, the alloy actually acts as an annode to the zinc. I think i have this right but if i dont then correct me because im no expert.
Tim

[Gorilla_in_Manila]

Jeffo,
Haven't heard of that one. I haven't heard of or seen it done, but I'm tending toward what Tim is suggesting, that it wouldn't be a good mix. Don't know for sure though.
Aluminium doesn't rust further because it immediately forms a thin layer of aluminium oxide on its surface (the greyish dull look). This then protects the rest of the aluminium from rusting (or oxidising) further.
What's the problem you are trying to stop?
Cheers,
Jeff

[jeffo]

i had a nav light leak..... corroded a hole in the sideoffmy boat about the size of a 20 cent peice. i hit it with inox to stop the corrosion, will this have done the trick?>?

[TimNQ]

If you sanded it back to a nice clean finish first then yea it will neatralise it id say as long as you have stopped the leak from the nav light. but it would be worth getting it patched id say.
Tim

[Gorilla_in_Manila]

I'd say as long as you cleaned the stuff off properly (ie give it a file or a sand) the aluminium will just form another oxide layer on its surface and won't go any further.
Guess you will need to patch it somehow. If the hole is located at a place where the boat flexes and if the hole has a ragged edge, you might find you start getting cracks running out from it. Might be best to file around the edges of the hole and smooth it out so there aren't any sharp notches from which the cracks might propogate. (same like drilling a hole in glass to stop the crack propogating)
Cheers
jeff

[Kerry]

Has this tinnie an outboard? then there should/will be an anode on it somewhere.

Specifically putting anodes directly onto the hull is getting into the black magic side of this type of issue and can in fact do more damage (if done incorrectly) than actually prevent it.

The issue causing your problem needs to be solved first and one question is why is it simply only around one nav light??

When you say "had a nav light leak", does that mean battery type nav lights? as if so then that's nothing an anode will prevent.

Cheers, Kerry.
#

[clutter]

Another thing to keep in mind when it comes to cancer and tinnies is you electronics, particularly your sounder. Most sounders are directly hooked to the battery and unless you disconnect the battery after every trip or pull the power lead out of the sounder there will be a small residual current going through your boat even though the power to the sounder may be turned off. Its a bit like when you turn off the telly with the stand by button, although the picture is off there is still power going to the unit.

Cheers Clutter

[jeffo]

kerry- when i put the nav lights on the boat i used silcone to prevent water getting inside the light (both outside and inside the boat). must have been a small gap somewhere and water got into my starboard side light, i spose the salt started corroding the wires and blub and then worked its way to the hull. its only a small hole and i intend to get it all fixedup shortly.
clutter-i take the head unit for my sounder out after each trip so i am guessing that ill do the trick?

i have also heard that all wiring needs to be run through conjute as .2 of a volt is all that is needed to start corrosion?

[Morlers]

Hey Jeffo
Was the silicone you used the neutral cure type (for metal guttering etc) or the normal acetic acid cure type (for glass, bathrooms etc). I understand the acetic acid cure type will corrode metals. This may be the cause of your problems.
Just a thought.
Morlers

[jeffo]

not sure morlers ??? my port nav light is still perfect... just the starboard thats causing greif.

[SNELLY]

Jeffo,

In all cases - especialy with an ally boat you should have an isolate switch - one swith and there is not current in anything - what I do is I buy the next largest battery box so that there is space at one end and install one of those red key isolate switches - then run your positive lead to the switch and a short cable from the other side of the switch to the positive terminal of your battery

Also I'm aware the a lot of alloy boats that are wired up in the factory and are earthed directly to the boat - this is also asking for trouble - with or without a switch as when the boat is in use its putting current through your hill