Old Goat wrote:
If you are going to do the loop, do you need to change your anodes from zinc to something else when you move from salt to fresh water?
*Ahoy Old Goat!
Due to considerable research I've accomplished (and am still accomplishing) - I hope this helps. - Cheers,*Art*
Anode protection is surely a necessary, yet a*difficult item to feel confident about which anode material is best in fresh water or in transition from salt to fresh... regarding*various hull and equipment materials:
That said I believe there is no need to change from zinc when in fresh water, under certain maintenance conditions.
2.4 years ago, with all locations on boat having new zincs installed just before we left SF Bay salt water, I began keeping our fiberglass Tollycraft tri cabin, twin screw with through hull shafts*in the*fresh water that is always present deep into SF Bay Deltas 1,100 miles of levee lined rivers and channels.* I had been informed that my zinc anodes would protect just fine as long as I consistently wire brush the surface build-up that forms in fresh water off them.* As the water is warm for swimming most of the year, and*I love to swim/dive with fins and mask, I greatly enjoy the fun-task of often keeping the zinc surfaces brushed clean.* I feel the often-cleaned zinc is doing a good job (cleaning once a month in spring, summer, and fall; with a span of several months during winter).* There is NO galvanization occurring on SS shafts and trim tabs or the, Bronze props, struts, rudders and through-hulls... I inspect it all very carefully with bright flashlight during each cleaning.* It appears that after this 2.4 year fresh water duration the zincs still have 50% +/- remaining material.* I plan to install new next spring... under current conditions.* Due to my concern re anodes in fresh water I researched many anode reviews, and listened closely to real-life-experience from boat owners.*
Ive come to this conclusion (for boats equipped like mine):
1.***** Zinc is absolute best anode for salt water (I already knew that from years of past experience)
2.***** Zinc is fine in fresh water as long as you can often wire brush the film that develops off the surfaces it lasts a long time too BUT... zinc surfaces must be brushed clean on a regular basis or the formed coating will eventually make the zinc inoperable
3.***** Magnesium is good to use in fresh water and evidently brushing its surface clean is not needed BUT... evidently mag will not last anywhere near as long as zinc (I havent tried Mag yet in fresh water, so I'm not in firsthand knowledge of its efficiency or duration of last ability.* I may try mag upon next anode change, but have found that unlike zinc, mag is not easily located in configurations that apply to all under hull apparatus)
That said; here are a couple anode items from experts that I feel tells it like it is!
Good to speak with you. I think you should be fine w/the amount of cleaning maintenance that you perform on zinc.* Your friends with the steel pontoons and Aluminum outdrive should consider using magnesium anodes. Not sure if they have a kit from Mercury, but it can be found on the net.
Here is a quick galvanic series table showing potentials/levels of metals.* Have fun up there in SF Delta!
Most Active (least noble) Anodes from top down with Least Active (most noble) Cathodes from bottom up:
Steel or Iron
Lead Tin solder
Stainless Steel (304)
Stainless Steel (316)
Regards, Harry Coulombe
Marine Division/Technical Sales / Farwest Corrosion Control Company
1480 W. Artesia Blvd. / Gardena, CA 90248
310-532-9524 X. 1116 main /
310-770-0652 mobile /
firstname.lastname@example.org **/ www.farwestcorrosion.com
I feel the following is a good report - Art
The Role of the Sacrificial Anode
By: Martin Wigg and Paul Fleury
Martin Wigg is president and founder of Performance Metals.* He holds an MBA and Bachelor of Science degree in mechanical engineering.* Paul Fleury is certified by American Boat and Yacht Council as an Electrical Technician and the National Association of Corrosion Engineers as a Corrosion Technologist
-- Edited by Art on Thursday 21st of July 2011 10:01:54 AM
-- Edited by Art on Thursday 21st of July 2011 10:16:12 AM
-- Edited by Art on Thursday 21st of July 2011 10:21:15 AM