Anode on the foils?

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Georg Weinstabl
Posts: 248
Joined: Fri Sep 04, 2009 7:27 am

Anode on the foils?

Post by Georg Weinstabl » Tue Nov 24, 2009 12:02 am

Hi everybody,

On the foils of my Volga we have encountered anodelike plates, that are bolted on them. These plates where having somekind of white crystals on them even growing 1,5 cm long. The boat was just lying in the harbour for 1,5 months in the water. but These were not existing when we put the boat to water and it was not ridden during that time at all. A quick tongue showed it not to be seawater salt but it must have been somekind of aluminiumoxyd and was tasteless. No odors, too. The plates was strongly corroded with holes and it was on all foils also on the front ones.

My question: There must be a function of this plate. I saw these plates only in the gallery once, but do not recall these plates being mentioned in any other comment and they were also not part of the anode blueprints shown.

Are these sacrificial anodes for protecting the stainless steel foils, for the hull itself or for both?
What is the material of these anodes? Same as the other ones?

Who has an idea? You may find photos of it enclosed.

Besides the anode, you can see the fabric, that is used for stuffing between the aluminium sheets.

Big craters are showing that
Attachments
IMG00068-20091107-1222MiracleAnodeClose.jpg
Big craters are showing that these plates have a function.
IMG00068-20091107-1222MiracleAnodeClose.jpg (34.62 KiB) Viewed 18826 times
IMG00069-20091107-1222MysteriousAnode.jpg
The anode is especially eroded at the waterline!
Georg
Motorboat ''Flying Carpet''
Istanbul

Robert
Posts: 12
Joined: Tue Nov 18, 2008 5:02 pm
Location: Finland

Re: Anode on the foils?

Post by Robert » Sun Nov 29, 2009 12:40 pm

Hi,

About the protection of aluminium hull, in our area we use in saltwater magnesium on the aluminium, and zink on the stainless.

This seems to work pretty good.Without the magnesium the corrosion is big, there will be big craters within some years.

I have some experience from my bigger vessel 17 m x 5.1 m, built in AlMg 4,5. Painted with epoxy primer 300 microns and Hempel Alusafe 2 layers.

Here I have created a voltage measuring system between hull and water to ensure right level of protection.
Voltage with no protection about 0,7 -0,8 V
with right protection 1,15 - 1,2 V
too much protection 1,3 ----- V

so it is a good battery which newer will be empthy, as long as there are some material left!

With too much magnesiun the result will also be destructive for the aluminium hull.
I use only portable magnesium rods which are hanging from the boat in a wire when in harbour.
On prop nuts I use Zinks. Props are alu-bronze and shafts stainless dia 70 mm. 2 of each.
During sea trawel there are no protection.
We built the boat 1996, and when protection is working, there are no problem. The bottom is like new when taking up in autumn.
One year I did not look after the protection wery good due to much traweling around the word, and the wire had bad contact to hull for about 2 mounths, then the bottom was full of small craters and spots where the primer came off. Had to blast the spots and paint again.

This boat use about 1,5 rod of dia 30mm and 1 m lenght each seson, from may to okt.

Each area is different, depending of the level of salt in water.

In lakes with soft water only zink is generally used.

Importand thing is, that all underwater parts in different material than aluminium have a high resistance to aluminium.

I have planned to test the same with Volgas, just to hang the right amount of magnesium from boat when in harbour.

I really do not know for which area the Volga original protection is planned, but will guess that Black Sea is one area, and it is very salty.
The magnesium anodes on Volga are really big in size compaired to the hull area under water.

Enclosed pick of that big boat "Lady Carin" with Wire and magnesium rod hanging at side.

BR

Flying Finn
Attachments
IMG_1386.JPG
Lady Carin

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Georg Weinstabl
Posts: 248
Joined: Fri Sep 04, 2009 7:27 am

Re: Anode on the foils?

Post by Georg Weinstabl » Tue Dec 01, 2009 8:37 pm

Hi Robert,

Wow! I see, that you are really scientifically approaching the matter. You are probably right, the Volgas have been invented to make party members, secretaries and maybe foreign tourists a joyful summer ride on the black sea. Some of them where also used in bigger cities (mainly in the south) to make tours on the rivers or lakes again for tourists. The rivers and lakes are freshwater and the Black Sea, that is being fed with fresh water from the Danube and most Russian rivers, namely Volga, Dnjestr, Dnjepr, Don and Volga. The Black Sea has at it's surface a very low salt water content because of this enormous fresh water supply and the salt water content is very comfortable for the eyes of a swimmer, comparing to the Egean or Mediteranean Seas. But this water being lighter than normal seawater is also streaming via the Bosphorus (Sea straight of Istanbul) to the Mediteranean and as an exchange we have salty sea water entering again via the same straight into the black sea approximately 30 m below the surface. Both of them having relatively strong currents.

I believe that our Volga Builders have taken in consideration all kind of uses for this boat and besides this also took in calculation the carelessness of their own people. So they probably prepared for the worst and gave the boat best possible protection with anodes of both
kinds.

Your idea of connecting wires with anodes to have them hang-down during standstills in harbours is striking and absolutely new for me. Probably nothing new for a Aluminium-boat owner, who may smile and say ''Good Morning!'' (Sorry, I am a newcomer and this is even my first boat!). From what you write else, I do understand, that the major issue is to have the boat primed and painted carefully and this in such way, that it is becoming LEAKPROOF for currency and all the electricity exchange has to be done by the anodes. This is the ABC for boats anyway, but probably nowhere so important like on Aluminium Hulls.

I shall therefor follow your advice with the materials of the anodes. Do you know about any kind of sources for original anodes, or do you prepare them for yourself? Are there places, where you can buy a complete set of anodes in Russia or in Europe for our boats?

Grateful for any reply, I remain with

best regards,
Georg
Motorboat ''Flying Carpet''
Istanbul

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