Running gear anti-fouling re-visited.

[rpell1@msn.com]

It seems that every year this issue comes to mind and this year is no exception. By chance, maybe, perhaps, somebody out there has come up with a solution to everyone's problem?

How do we keep our prop and shaft free from marine growth?

I've already tried primers with anti-fouling layered over, teflon waxes, teflon grease, never-seize, moly-grease, magic wishes, prayers...............

No luck with any of these except cleaning at the beginning of the season and diving periodically, (which is getting more and more difficult as the years pile on.....and too cheap to hire someone).

So............I pose the question again and hope there is a new discovery?

 

[RichH]

Petit Zinc Rich Barnacle Barrier (spray).
Should be applied 'smooth' or wet-sanded to 'babies ass smooth' so that the prop rotation quickly sheds the slime upon which barnacles can get a foothold.

 

[Charles Erwin]

Ralph and Rich:

Is there anything to the notion that galvanic potential of the shaft/prop/zinc assembly promotes or discourages such growth?

For example, the shaft/prop/zinc assembly on my boat is electrically isolated from the rest of the underwater metals (the neighbors too for that matter) because the shaft terminates via a "shaft saver" - thus in my case the shaft/propeller/zinc assembly is not electrically connected to anything else in the boat nor to any other boat because it is not connected to the safety green to onshore.

I have had virtually no growth on the shaft/propeller assembly over 5 years time, whereas I do have about the same growth as everyone else on the hull surface.

By the way my location is Puget Sound and that may make a difference.

Charles

 

[RichH]

Charles,
I havent done the electro potential calcs. of isolated or even zinc-less applications vs. bronze props; but, when I had a boat with ONLY a shaft zinc and that zinc fell off ... I never had a barnacle. So yes, it seems that if the base metal is being attacked electrochemically, at least the hard growth will not attach ... probably due to stray currents generated which are dissolving the minute amounts of zinc (added for 'machinability') within the 'bronze' and the currents are 'irritating' to the hard growth.

I do know and have experienced/observed that when boats are 'over-zinced' (too big an anode) the barnacles seem to be attracted to a much greater degree.

The obvious answer is to use a calibrated standard cell (corrosion resistance electrode) and assay the ACTUAL electro-potentials .... and not guess. The cell will indicate how much mass/surface area of anode is CORRECT.

;-)

 

[Charles Erwin]

Is there anything in facts underlying these events that could reduce growth?

 

[navigator97]

For the last 3 seasons, I have used the Pettit Barnacle barrier spray also and have had good results with it (I'll see again when we haul in a week how it did this year). I also have used 3 "football shaped" zincs on my 1" shaft. I coat a very clean shaft and prop with the spray after masking the zincs applied to the bare shaft. So fa so good.

 

[rpell1@msn.com]

Thanks. I haven't tried that yet.

 

[rpell1@msn.com]

Sorry. "Somehow" my reply got itself attached to my initial post. Gee, I wonder how that happened?

 

[rpell1@msn.com]

Thanks Rich H. Do you know where I might get more information on the subject?

Although, I am in a low salinity area which has alot of residual current. I only have one shaft zinc and also have a galvanic isolator hooked up to shore power.

I would like to investigate this further. Thanks again.

 

[RichH]

Thanks Rich H. Do you know where I might get more information on the subject?

Although, I am in a low salinity area which has alot of residual current. I only have one shaft zinc and also have a galvanic isolator hooked up to shore power.

I would like to investigate this further. Thanks again.

PM me with your email address. I have a .pdf copy of the "Corrosion Reference Electrode
User’s Guide" from 'boatzincs.com'. This used to be available free from their website, but now is only included when you purchase their standard reference cell. You can also search the boatzincs.com website - I cant seem to find the guide on this website anymore. This guide is a good starting point for 'electrolysis', etc. There are other reference works on the net but you'll have to do your own websearch: Corrosion + electrolysis + guide + boat, etc.

eg.: http://yachtpals.com/how-to/electrolysis ... an electrolytic corrosion 'forum'.

 

[rpell1@msn.com]

Many thanks Rich. my e-mail is rpell1@msn.com

Happy Sailing.

 

[tomgrigsby]

Propspeed

 

[jsalley]

Propspeed

+1. Great stuff, but requires a second mortgage to purchase the kit.