Aluminum electrolysis prevention state of art

[Patrick BLOSSE]

Hello,

I am looking for a completion of my own french library on the state of art, viewed from international waters, concerning electrolysis concerns about aluminum yachts, not only based on principles but precisely quantified with data, for the design and, overall, for maintenance purposes during the life cycle of the yacht.

Thank you in advance for contributing.

Fair winds to all.

Patrick

[MikeJohns]

Not quite sure what you are after Patrick. Are you looking at electrolysis (stray current cause) or galvanic corrosion/anodic protection ?

[Patrick BLOSSE]

Thank you for your reply Mike,

Generaly speaking anyone can rather easily obtain general information about aluminum hull electrolysis risks: direct stray currents, galvanic corrosion, corrosion under strain, Evan's effet and so on.

More rarely the point of view from feed back maintenance engineering is available: how did problems occur, what were the measurements obtained, what where the solutions involved and the limits admitted, what was the final satisfaction in any type of corrosion treatment ?

Thank you in advance for contributing.

Fair winds and smooth seas to all.

Patrick

[MikeJohns]

Patrick if its any use I have experienced problems as follows:

Adverse reaction with lead ballast poured directly into an alloy keel and wet bilge. Plating corroded right through.

Significant and expensive Shaft tunnel corrosion in one ferry

Integrated water tanks in several vessels left unpainted, one corroded through the hull plate itself within 5 years.

Salt water exhaust exit in hull side of a fast ferry casued a significant problem

Signifiacant corrosion in stabilizer fin seal housing.

And the solutions... following repair, good preparation and high build coatings and even waterproof grease and regular inspections.

[Patrick BLOSSE]

Mike,

I already faced or heard of similar reactions, as those described, of course.

Do you know active electrolysis prevention devices -such as these installed on large steel carriers and using reversed voltage, placing Aluminum above most other metals encountered, in the scale to be considered- used onboard small yachts ?

Thank you.

Patrick

[MikeJohns]

Active cathodic protection systems do get used here on small craft where the owners like high tech gadgets and of course there are the outboards that try and use this system to varying degrees of success.

They don't have a good name here on small boats, and are never as robust or as reliable as sacrificial anodes and they have a reputation here for being unreliable on small craft. High tech electronic devices in a marine environment that need reasonably frequent monitoring says it all. We have a large Aluminium boat and small ship industry and these devices have not found favour here.

Problems nearly always occur becasue the vessels onboard batteries have gone flat becasue the charging circuits/devices/batteries have been compromised. The big problems using these systems on smaller boats is simply the power requirement if the coating has been damaged.

They also need a clean regular maintenance program and if the electrodes have been fouled they can also stop working or go to max voltage trying to get the reference electrode voltage to the desired reading.

A top quality bulletproof (expensive) system would be a good option on a large power yacht regulalrly hauled.

If the electrodes can be disconnected then the vessel can be proteced with guppy anodes when moored for long periods abd the active system switched off.

I'm not an expert on this and these are my observations. It would be interesing to hear from the proponents and manufacturers.

[Patrick BLOSSE]

Mike,

Thank you very much for all that convincing contribution.
Anyway, can you direct me towards more data about theses small craft devices, please ?

On an other hand, do you have any data about limits and conditions for stray currents (or voltage/insulation levels) to be considered critical for small craft aluminum hulls ?

Kindly.

Patrick

[LyndonJ]

Cathelco in the UK have a good name here and I recommend that you contact them and ask for their information on 'ICCP' for small alluminium boats.

http://www.cathelco.com/

cheers

[Patrick BLOSSE]

Hello,

Thank you for your contribution.
Do you have some more information to share about standards in use overseas, I mean about anodes and/or coatings and insulation levels to be observed for classification and/or maintenance purposes ?

Patrick