Anode material...how to tell?

BeaufortTJustice

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My research indicates that there is at least three common materials that anodes are made from - depending on water use (salt, fresh, brackish). Can you tell by looking at them which material it is? The ones on my drive have no visible numbers or other identifying information. Any help is much appreciated.
 

havasuboatman

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Re: Anode material...how to tell?

If there are no markings, that generally means you have zinc annodes
 

BeaufortTJustice

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Re: Anode material...how to tell?

If there are no markings, that generally means you have zinc annodes

Is it possible it had markings at one time and they have been eaten away? If so, is there a way to tell other than presence or absence of numbers?
 

havasuboatman

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Re: Anode material...how to tell?

When they are new, the zinc isn't as shiney.
Zinc oxidises quicker than the other alloys (thereby protecting your boat better, in my opinion.)
Your boat is only 2 yrs old, is it in the water all the time? you shouldn't have too much erosion, I would think.
I guess you could shave a sliver of yours off and try to burn it. If it flashes bright white to an open flame, it's magnesium.
 

Snobike Mike

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Re: Anode material...how to tell?

Very hard to tell without numbers.

if you have a boat sold in a fresh water area it will most likely have aluminum anodes because those are for brackish so it essentially gives you "some" coverage both ways (salt and pure fresh).

When I recieved my boat I specifically asked them to confirm the type of anodes and had them switch them to magnesium because I'm fresh water only.

The mag anodes looked a little darker than the aluminum but I don't think you can use that as a way to verify your anodes since unless they are new they would be worn/discolored from the water you're in.

In most cases anodes aren't that expensive. If you're unsure just get new ones and you're off to the races.
 

Snobike Mike

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Re: Anode material...how to tell?

Another thing.

According to the anode chart I looked at the magnesium anodes are about half the weight of the aluminum ones. Magnesium will be the lightest of the 3 metals.
 

bruceb58

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Re: Anode material...how to tell?

Zinc oxidises quicker than the other alloys (thereby protecting your boat better, in my opinion.)
Actually, the oxidation coating on the zincs needs to be removed in order for them to work properly. Magnesium is less noble than zinc and therefor will protect more.


BeaufortTJustice,

What condition are the anodes? Are they eaten away a lot? You moor your boat for long periods at a time? Salt or fresh?
 

myoldboat2

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Re: Anode material...how to tell?

As long as the anode is made of one material, you can measure it's density.

1. Weigh it and convert ounces to pounds, e.g. 1.3 oz / ( 16 oz/lb ) = 0.08 lb.
(or you can work in grams, e.g. 37 g)

2. Dunk it in a measuring cup with some water and measure it's volume. The mL scale should be more accurate than the fluid oz scale. Then convert to cubic inches, e.g. 14 mL / ( 16.4 mL/in^3 ) = 0.85 in^3
(or work in grams and leave the volume in mL, e.g. 14 mL)

3. Divide the weight by the volume to get the (weight) density, e.g. 0.08 lb / 0.85 in^3 = 0.094 lb/in^3
(or 37 g / 14 mL = 2.6 g/mL mass density)

4. Compare to the known densities
Magnesium .063 lb/in^3 (1.7 g/mL)
Aluminum .098 lb/in^3 (2.7 g/mL)
Zinc .26 lb/in^3 (7.1 g/mL)

So the example above would've been for an aluminum alloy anode.


Comment: The zinc alloy used really is mostly zinc. Military specification MIL-A-18001K calls out 99.314% zinc minimum, with very small amounts of aluminum, copper, cadmium, iron and lead. So you should just be able to compare to the density of pure zinc. Magnesium alloy and aluminum alloy anodes are similar--mostly made of magnesium or aluminum.
 

ErieRon

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Re: Anode material...how to tell?

myold boat2;

I have OCD too...that was awesome:D
 

bruceb58

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Re: Anode material...how to tell?

Problem is that the aluminum ones are really an alloy...then what do you do?
 

BeaufortTJustice

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Re: Anode material...how to tell?

I garage my boat in between daytrips to lake. I don't think it was ever moored or kept in the water for significant length of time. As far as condition, it doesn't look like it is eaten way much, so I assume if there were numbers or anything they would still be there. They have the color of lead - kinda light grey with a light colored "patina" on the outside. If you scrape the outer layer, it is shiny silver. It obviously is not as heavy as lead. I think I'll try the flame method mentioned above, that sounds the most exciting. If that proves inconclusive, then I'll try the scientific method.

Thanks guys for the help...I want to make sure I have magnesium and am hoping that is what I currently have (one less thing to buy if I already have them).

Happy boating (err, rather, happy winterizing, for now)
 

bruceb58

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Re: Anode material...how to tell?

If you are not leaving your boat in the water 24/7 there is no reason to change out your anodes unless they are getting totally eaten away which I doubt they are.
 

BeaufortTJustice

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Re: Anode material...how to tell?

If you are not leaving your boat in the water 24/7 there is no reason to change out your anodes unless they are getting totally eaten away which I doubt they are.

...So I am worrying about something that is a non-issue based on my usage pattern...thank you for bringing me down to earth...I won't worry about it then,

Thanks again, guys.
 

PiratePast40

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Re: Anode material...how to tell?

^^^^
but the flame test would still be pretty cool if it was pure magnesium :D
 

bruceb58

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Re: Anode material...how to tell?

They don't come with magnesium from the factory so I doubt it.
 

myoldboat2

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Re: Anode material...how to tell?

Problem is that the aluminum ones are really an alloy...then what do you do?

Not a problem, the aluminum alloy densities are near the listed value; see here for example.

You can look at the Mercruiser fin on page 25 (pdf page 26) of this catalog. For example, the CM31640 part weights follow the ratios of the listed densities: zinc 1.21 lb (0.55kg), aluminum 0.46 lb (0.21kg), magnesium 0.3 lb (0.14kg)


ErieRon said:
I have OCD too...

shhhh, don't give us away... :cool:
 
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