Judders
Active member
How often?
Replacing Anodes
- Thread starter Judders
- Start date
S
Skyva_2
Guest
Some would say every year.
Personally, if a hull anode erodes less than 25% in a year I would leave it till next lift. A shaft anode I would replace.
Personally, if a hull anode erodes less than 25% in a year I would leave it till next lift. A shaft anode I would replace.
Niander
New member
Im a bit confused with these anodes?
am i right in thinking you should use them connected to the metal if you have a mix of metals under the surface?
am i right in thinking you should use them connected to the metal if you have a mix of metals under the surface?
Dave99
Member
The industry rule is if it is at less than 50% then in needs replacing. However in some cases it may be better to do it sooner. For instance on a big boat if you replace all the anodes you may be able to leave the boat in the water for 2 years instead of one - reducing you lift out costs.
S
Skyva_2
Guest
FullCircle
Well-known member
I am trying to 'rotate' my shaft anodes. I have 2 on the shaft, the 25mm spherical type (www.zincsmart.com) I am experimenting with fitting one half way through the season to avoid them both corroding away at the same time.
Also next year, I am fitting a 2.3kg pear anode to see what that does in ternms of longevity.
I dont use marinas much, but I am also fitting a galvanic isolator to the shorepower circuit which helps a lot when I am in marinas, like now.
Averagely, my shaft anodes do one season and are just about gone between april and november.
Also next year, I am fitting a 2.3kg pear anode to see what that does in ternms of longevity.
I dont use marinas much, but I am also fitting a galvanic isolator to the shorepower circuit which helps a lot when I am in marinas, like now.
Averagely, my shaft anodes do one season and are just about gone between april and november.
VicS
Well-known member
[ QUOTE ]
Im a bit confused with these anodes
[/ QUOTE ] To be effective an anode must be reasonably close to the item(s) it is to protect and electrically bonded to them with a good low resistance electrical connection. The anode should also be within "line of sight" of the item it is to protect although that does not have to be taken too literally as anodes can "see round slight curves.
The electrical bonding usually means that all the bits to be protected and the anodes are all interconnected internally and also to te engine block with heavy gauge cable. Except that non-ferrous fittings should not be connected to the same anodes as ferrous items. Bronze and DZR brass should not normally need cathodic protection anyway.
If internal connection is not possible then the anode can be bolted directly to the item it is to protect with good electrical contact. Steel rudder blades for example which will need an anode on each side.
In addition to the link Skysail has given seek out MGDuff's website. You will be surprised at the size of cable recommended for the bonding.
Im a bit confused with these anodes
[/ QUOTE ] To be effective an anode must be reasonably close to the item(s) it is to protect and electrically bonded to them with a good low resistance electrical connection. The anode should also be within "line of sight" of the item it is to protect although that does not have to be taken too literally as anodes can "see round slight curves.
The electrical bonding usually means that all the bits to be protected and the anodes are all interconnected internally and also to te engine block with heavy gauge cable. Except that non-ferrous fittings should not be connected to the same anodes as ferrous items. Bronze and DZR brass should not normally need cathodic protection anyway.
If internal connection is not possible then the anode can be bolted directly to the item it is to protect with good electrical contact. Steel rudder blades for example which will need an anode on each side.
In addition to the link Skysail has given seek out MGDuff's website. You will be surprised at the size of cable recommended for the bonding.
Clyde_Wanderer
New member
VicS, Further to your above post, I have some s/s 1/2" ball valves screwed onto brass/bronze through hulls, and a 11/2" bronze gate valve onto a bronze through hull.
Should I have all the above through hulls connected to the hull annode by Heavy duty (or what size) cable?
Also how will I know what is ferous or non ferous?
Thanks.
Should I have all the above through hulls connected to the hull annode by Heavy duty (or what size) cable?
Also how will I know what is ferous or non ferous?
Thanks.
roly_voya
New member
Ferous is anything with steel in it inc stainless, non-ferus is anything else. The broze gate valve should not be vunerable unless conected to anything electrical but the stainless/bronze combination could need protection
VicS
Well-known member
Bronze on bronze should be Ok in fact that is the best and in all normal situations should not need any cathodic protection so do not connect it to anything.
Stainless steel below the water line is always a bit dubious. It must be A4 not A2.
Brass must be DZR(Dezincification resistant) but even that is second best to bronze. I do not see any problem in the stainless being screwed onto bronze or brass. The mechanism by which stainless steel is protected from corrosion, namely by an oxide film, will actually be enhanced if anything by the very small difference between it and bronze or brass in the galvanic series. Again these should not require cathodic protection so should not be wired to anything else. I think the stainless valve and the skin fitting if it is brass should be inspected carefully every year for any signs of corrosion or dezincification. If any problem is detected then the alternatives are to replace with bronze (or plastic) or connect to their own dedicated anode(s).
By ferrous I was meaning iron or steel but for this purpose excluding stainless steel. So it'll be magnetic and/or rusty!
By non ferrous I was meaning copper alloys namely brass and bronze. It is unfortunately almost impossible to distinguish between brass and bronze (other than by chemical or spectroscopic analysis) and even more difficult to distinguish DZR brass from "ordinary" brass. If there is any sign of pink colouration then the alarm bells should ring loudly.
Stainless steel and cathodic protection is an interesting topic bcause as I said earlier st st is protected from corrosion by an oxide film. If cathodic protection is applied the first thing that happens is that this film is lost. The stainless has effectivly lost its stainless properties and is then protected from corrosion in exactly the same way as iron or ordinary mild steel. If cathodic protection is applied it must not be done in a half hearted way on the basis that stainless doesn't corrode anyway, especially in contact with a copper alloy.
Regarding the cable size for connecting any anodes you do have MGDuff recommend a minimum of 4mm² PVC covered multistrand cable. That is pretty heavy.
Stainless steel below the water line is always a bit dubious. It must be A4 not A2.
Brass must be DZR(Dezincification resistant) but even that is second best to bronze. I do not see any problem in the stainless being screwed onto bronze or brass. The mechanism by which stainless steel is protected from corrosion, namely by an oxide film, will actually be enhanced if anything by the very small difference between it and bronze or brass in the galvanic series. Again these should not require cathodic protection so should not be wired to anything else. I think the stainless valve and the skin fitting if it is brass should be inspected carefully every year for any signs of corrosion or dezincification. If any problem is detected then the alternatives are to replace with bronze (or plastic) or connect to their own dedicated anode(s).
By ferrous I was meaning iron or steel but for this purpose excluding stainless steel. So it'll be magnetic and/or rusty!
By non ferrous I was meaning copper alloys namely brass and bronze. It is unfortunately almost impossible to distinguish between brass and bronze (other than by chemical or spectroscopic analysis) and even more difficult to distinguish DZR brass from "ordinary" brass. If there is any sign of pink colouration then the alarm bells should ring loudly.
Stainless steel and cathodic protection is an interesting topic bcause as I said earlier st st is protected from corrosion by an oxide film. If cathodic protection is applied the first thing that happens is that this film is lost. The stainless has effectivly lost its stainless properties and is then protected from corrosion in exactly the same way as iron or ordinary mild steel. If cathodic protection is applied it must not be done in a half hearted way on the basis that stainless doesn't corrode anyway, especially in contact with a copper alloy.
Regarding the cable size for connecting any anodes you do have MGDuff recommend a minimum of 4mm² PVC covered multistrand cable. That is pretty heavy.
Sandyman
Well-known member
On the subject of anodes. A friend recently replaced two shaft anodes with new one's of the wrong size, which didnt make full contact around the shaft. I pointed out to him the error of his ways but he choose not to listen to this 55 year old time served marine electrical engineer. Guess he will learn the hard way.
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