Blackwater anode

[rbeange]

Hi, I've bough an aluminium anode for use in the estuary/sea in this area. I would be grateful if someone could confirm that is the correct choice for the Blackwater.

Thank you

 

[macd]

Aluminium, as you no doubt know, is for use in brackish water, which is something of an inaccurate definition. From my own experience in a brackish (river-fed) harbour, sometimes normal zinc anodes work, sometimes not (due to build-up of impervious coating of zinc hydroxide?). It seems to vary from boat to boat, no doubt due to the precise electrolytic circumstances of each, or even where they were moored relative to the main river flow. Nonetheless, it may be helpful to check what other boats in the area are using.

In my case I had a distinct coating on the anode and so went for aluminium anodes. These seemed to work satisfactorily both when moored in the brackish harbour, and after I left long-term.

 

[VicS]

Hi, I've bough an aluminium anode for use in the estuary/sea in this area. I would be grateful if someone could confirm that is the correct choice for the Blackwater.

Thank you

Yes aluminium would be a good choice for the Blackwater. It is suitable for brackish and sea water while zinc is only suitable for sea water

 

[rbeange]

Thank you. I ask as the previous hull anode (it was moored elsewhere, but still in an estuary, until last year) was much heavier - I assume it was zinc.

 

[tillergirl]

Forgive me disagreeing with the esteem VicS for once but the River Blackwater is not a river but a ria - a drowned river valley. It is also known as the saltiest river (see John Leather's book) and for that reason at the head of the River they take out salt for Maldon Sea Salt. Do not regard the Blackwater as brackish. It isn't. Go for Zinc.

 

[VicS]

Forgive me disagreeing with the esteem VicS for once but the River Blackwater is not a river but a ria - a drowned river valley. It is also known as the saltiest river (see John Leather's book) and for that reason at the head of the River they take out salt for Maldon Sea Salt. Do not regard the Blackwater as brackish. It isn't. Go for Zinc.

Id forgotten about the Salt works at Maldon. So either zinc or aluminium will be suitable

 

[ianfr]

Hi

Based as I am on the Blackwater, ZINC is the correct anode to use.

The ONLY place where Aluminium would be suitable would be in Heybridge basin or the canal.

Regards

Ian

 

[rbeange]

My understanding was that Aluminium was ok in salt water and brackish water, while zinc was ok for salt water. Sorry to labour the point, but I'm back in the water now and I don't want to compound one mistake with another....

 

[vyv_cox]

Aluminium seems to work perfectly well on thousands of offshore structures and ships. OK it is protecting steel rather than bronze/brass/stainless steel but it should still be OK on your boat.

 

[corinthmistral]

+1 for Zinc
Also in Blackwater / Tollesbury marina
Blackwater is definitely not brackish and saildrive anodes (without boat connected to shore power) generally last me two seasons.

 

[davidej]

An interesting aside...

I read somewhere that the origin of the name Blackwater is a corruption of Brackwater ie brackish water

 

[omega2]

Always fitted zinc up to last year, have fitted Ally now, was told they are just as good and last a little longer (we will see) we haul out bi annually, and in the past the zincs have been 75% worn. Ally are also a good bit cheaper.
http://www.zincsmart.com/

or this one is close to home?

http://anodesdirect.co.uk/joomla/

 

[rbeange]

Yeah, I called McDuff and Z-Guard, both told me aluminium would be fine in salt water. But I'm new to this and the lack of a consensus is making me nervous.....

 

[MoodySabre]

Can you dry out somewhere mid-season and have a look at it?

I use zinc but that's because I always have and the previous owner did. If the people who sell them aren't worried then I'd be relaxed about.

 

[vyv_cox]

Yeah, I called McDuff and Z-Guard, both told me aluminium would be fine in salt water. But I'm new to this and the lack of a consensus is making me nervous.....

No reason to be nervous, 'lack of a consensus' is perfectly normal on these forums

There are two considerations.
1.The anode needs to be negative in the Galvanic Series in Seawater http://www.corrosionist.com/Galvanic_Series_of_Metal_in_Seawater.htm by comparison with the object being protected
2. It should be chemically compatible with the environment, e.g. magnesium complies with 1. but is rapidly corroded away in seawater, and zinc develops an impervious layer in fresh water.

So aluminium is perfectly acceptable, is recommended by the manufacturer and is widely used throughout marine industries.

 

[omega2]

Yeah, I called McDuff and Z-Guard, both told me aluminium would be fine in salt water. But I'm new to this and the lack of a consensus is making me nervous.....

So whats your problem? just because a few dinosaurs on here say different does not make them right. I am a dinosaur myself, gotta be still running Ford Sabres, in a 27year old Aquabell.

 

[rbeange]

Thank you all, I will try not to stress.....

 

[VicS]

Thank you all, I will try not to stress.....

This looks a well written article http://www.martyranodes.com/content/martyr-resources/Aluminum Anodes.pdf Read and relax!