In situ replacement of hull anode??

[Mike k]

I would be grateful for any views on whether its easily do-able to change the hull anode in the water and for any tips and techniques.

I currently have a 4/5 inch disc zinc anode with a recessed fixing point( dimple in the middle) fixed to the GRP transom just below the waterline. I can reach it reasonably easily.

Is it just a question of removing nut and washer placing new one on and replace washer and nut ??

Secondly is bigger better?

It would be great if this was possible because then I can delay expensive lift out.

many thanks in advance

Mike

 

[superheat6k]

You are assuming there is an inner nut sealing the stud through the hull. If you don't know this then it might be better to wait the lift out. In this case a simple dangling anode will suffice. Connect to the bonding circuit and hang near the worn out anode.

Remember to pull it in before you use the boat.

 

[longjohnsilver]

You are assuming there is an inner nut sealing the stud through the hull. If you don't know this then it might be better to wait the lift out.

Is there any other way? I've changed loads of anodes in/underwater, quite easy to do. Just make sure you don't drop either the new anode or the nut and washer!

 

[omega2]

Ask yourself this, how is it fixed? if its just a through bolt can I get to the inside end to hold it so that I can undo the outside one. or if as suggested the inside end is laminated into the transom then what happens if I disturb it and let in water, can I get get a repair done whilst water is pouring in. Can I get at the inside and hacksaw it off. If you do get the bolt out then have a new bolt/washer/nut ready to refit, and a tube of sikaflex.

 

[Ripster]

IMO yes you can do it, if its just a dome type held on by a lock nut and washer. As others have said though, check what the stud is and what is on the other end. The risk is that if its a bolt or stud just pinched through the hull with sealer, then these can easily twist under a spanner and unseal and thus you have a leak! Have a partner on the inside if its this type bracing with a spanner an watching carefully and be very gentle with your undoing. If it is not coming off reasonably easily, stop and use a supplementary hanging anode until you can get a lift. Good luck with it.

 

[maby]

As above - it's easy if it's been fitted properly. If you have never taken it apart before and cannot track down someone who has, then proceed with caution!

 

[omega2]

Who on here has found the retaining bolts on anodes to be rusted away to nothing? and when tackled they just break off, you then need a new set of anode bolts, and diver or a good large capacity pump, NO do it when the boat is on the hard.

 

[maby]

Who on here has found the retaining bolts on anodes to be rusted away to nothing? and when tackled they just break off, you then need a new set of anode bolts, and diver or a good large capacity pump, NO do it when the boat is on the hard.

I would be very concerned if my anode retaining bolt had rusted away - that is what the anode is there to avoid! If it's failed to protect the retaining bolt, there's no hope for the propshaft!

 

[RobWales]

I would be very concerned if my anode retaining bolt had rusted away - that is what the anode is there to avoid! If it's failed to protect the retaining bolt, there's no hope for the propshaft!

Big difference between rust and galvanic damage though!

Anodes have nothing at all to do with rust sorry.

 

[omega2]

I would be very concerned if my anode retaining bolt had rusted away - that is what the anode is there to avoid! If it's failed to protect the retaining bolt, there's no hope for the propshaft!

you have obviously never been under and removed an anode yet, come back when you have.

http://www.asap-supplies.com/marine/anode-bolts-and-fixings

 

[maby]

you have obviously never been under and removed an anode yet, come back when you have.

http://www.asap-supplies.com/marine/anode-bolts-and-fixings

I've replaced multiple anodes - never had any problem with corrosion - perhaps I've been lucky! Not all on new boats either...

 

[RobWales]

I've replaced multiple anodes - never had any problem with corrosion - perhaps I've been lucky! Not all on new boats either...

Ermm confused here, I refer you to your earlier statement..................................

"I would be very concerned if my anode retaining bolt had rusted away - that is what the anode is there to avoid! If it's failed to protect the retaining bolt, there's no hope for the propshaft!"

I repeat ANODES DO NOT PROTECT AGAINST CORROSION!.......

 

[maby]

Ermm confused here, I refer you to your earlier statement..................................

"I would be very concerned if my anode retaining bolt had rusted away - that is what the anode is there to avoid! If it's failed to protect the retaining bolt, there's no hope for the propshaft!"

I repeat ANODES DO NOT PROTECT AGAINST CORROSION!.......

I beg to differ:

http://www.evrigard.com.au/electronic-rust-protection-technologies

http://en.wikipedia.org/wiki/Galvanization

http://www.dynamicscience.com.au/tester/solutions/chemistry/corrosion/rustpreventionsacanode.htm

"Cathodic protection[edit]Main article: Cathodic protection
Cathodic protection is a technique used to inhibit corrosion on buried or immersed structures by supplying an electrical charge that suppresses the electro-chemical reaction. If correctly applied, corrosion can be stopped completely. In its simplest form, it is achieved by attaching a sacrificial anode , thereby making the iron or steel the cathode in the cell formed. The sacrificial anode must be made from something with a more negative electrode potential than the iron or steel, commonly zinc, aluminium, or magnesium. The sacrificial anode will eventually corrode away, ceasing its protective action unless it is replaced in a timely manner. Cathodic protection can also be provided by using a special-purpose electrical device to appropriately induce an electric charge

" (Wikipedia)

 

[RobWales]

I beg to differ:

http://www.evrigard.com.au/electronic-rust-protection-technologies

http://en.wikipedia.org/wiki/Galvanization

http://www.dynamicscience.com.au/tester/solutions/chemistry/corrosion/rustpreventionsacanode.htm

"Cathodic protection[edit]Main article: Cathodic protection
Cathodic protection is a technique used to inhibit corrosion on buried or immersed structures by supplying an electrical charge that suppresses the electro-chemical reaction. If correctly applied, corrosion can be stopped completely. In its simplest form, it is achieved by attaching a sacrificial anode , thereby making the iron or steel the cathode in the cell formed. The sacrificial anode must be made from something with a more negative electrode potential than the iron or steel, commonly zinc, aluminium, or magnesium. The sacrificial anode will eventually corrode away, ceasing its protective action unless it is replaced in a timely manner. Cathodic protection can also be provided by using a special-purpose electrical device to appropriately induce an electric charge


" (Wikipedia)

100% in agreement, but the corrosion being reffered to is not RUST!

 

[maby]

100% in agreement, but the corrosion being reffered to is not RUST!

Did you read any of the web pages referenced?

"
Electronic Rust Protection Technologies

There are a number of electronic rust protection technologies used, some more effective than others and some only suited to certain applications but ineffective for use on motor vehicles. Below is an overview of the various forms of ERP and the benefits and limitations associated with them:

Sacrificial Anode Technology (Cathodic Protection) Stand-alone or Electronic:
"


"Galvanisation is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. The term is derived from the name of Italian scientist Luigi Galvani. Although galvanisation can be done with electrochemical and electrodeposition processes, the most common method in current use is hot-dip galvanization, in which steel parts are submerged in a bath of molten zinc. In industry, the term GI stands for galvanised iron, referring to a common galvanised steel used in many applications such as air ducts and trash cans."


"Iron is a cheap and strong metal to use as a construction material. It has one basic flaw however, it is very reactive. It will quickly rust, under the right conditions, leaving behind a fine brown powder known as iron oxide(rust). We can prevent iron from rusting
by many different methods. The most common way is to paint the metal and prevent oxygen from reacting with it. This method is very expensive as coats of paint need to be applied frequently. If the surface coating of paint is scratched rusting will take place immediately. This is not the preferred method of rust prevention for giant ships that often scrape against rocks, sand and barnacles. Instead, a sacrificial anode is used. A sacrificial anode is a block of metal that is more reactive than iron. The more reactive a metal is the easier it gives away electrons. This reactive block of metal acts as a source of electrons for the iron. When oxygen takes electrons from the iron during the process of rusting iron atoms simply take electrons from the reactive metal."

 

[omega2]

I've replaced multiple anodes - never had any problem with corrosion - perhaps I've been lucky! Not all on new boats either...

give it time!!

 

[RobWales]

Did you read any of the web pages referenced?

"
Electronic Rust Protection Technologies

There are a number of electronic rust protection technologies used, some more effective than others and some only suited to certain applications but ineffective for use on motor vehicles. Below is an overview of the various forms of ERP and the benefits and limitations associated with them:

Sacrificial Anode Technology (Cathodic Protection) Stand-alone or Electronic:
"


"Galvanisation is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. The term is derived from the name of Italian scientist Luigi Galvani. Although galvanisation can be done with electrochemical and electrodeposition processes, the most common method in current use is hot-dip galvanization, in which steel parts are submerged in a bath of molten zinc. In industry, the term GI stands for galvanised iron, referring to a common galvanised steel used in many applications such as air ducts and trash cans."


"Iron is a cheap and strong metal to use as a construction material. It has one basic flaw however, it is very reactive. It will quickly rust, under the right conditions, leaving behind a fine brown powder known as iron oxide(rust). We can prevent iron from rusting
by many different methods. The most common way is to paint the metal and prevent oxygen from reacting with it. This method is very expensive as coats of paint need to be applied frequently. If the surface coating of paint is scratched rusting will take place immediately. This is not the preferred method of rust prevention for giant ships that often scrape against rocks, sand and barnacles. Instead, a sacrificial anode is used. A sacrificial anode is a block of metal that is more reactive than iron. The more reactive a metal is the easier it gives away electrons. This reactive block of metal acts as a source of electrons for the iron. When oxygen takes electrons from the iron during the process of rusting iron atoms simply take electrons from the reactive metal."

Well we learn somethig new everyday I guess, I offer my apologies and stand corrected!

 

[omega2]

Well we learn somethig new everyday I guess, I offer my apologies and stand corrected!

You can give in if you like Rob, but WHAT MADE OUR BOLTS CRUMBLE?? and others I have come across "My anodes are untouched and they have been on for over a year" the reason was found to be that the bolts holding them were in two pieces and the only thing holding them in place was the sikaflex sealant.

 

[maby]

Well we learn somethig new everyday I guess, I offer my apologies and stand corrected!

"Rust" is just the common term for corrosion of iron!

 

[maby]

You can give in if you like Rob, but WHAT MADE OUR BOLTS CRUMBLE?? and others I have come across "My anodes are untouched and they have been on for over a year" the reason was found to be that the bolts holding them were in two pieces and the only thing holding them in place was the sikaflex sealant.

Anodes rely on good electrical connection to work - if the mating surfaces are not very clean, they will not work; if the bolts are not adequately tightened so that water can get between the anode and the bolt, then they will gradually stop working. If you find that your anode mounting bolts are corroding (as in rusting), then something is wrong and the anodes are not protecting the rest of the boat either.