Using the proper 'Zinc' for your boat

B

baz

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Fluid Motion Model
C-24 C
Subject: Using the proper 'Zinc' for your boat

The following was taken from Defender at http://www.defender.com/html/zincs_info.html

Zinc Alloy Anodes = Salt water only
  • Not recommended for use in fresh water
    Alloy is manufactured to meet or exceed US Military Specification (MIL-A-18001K)

Aluminum Alloy Anodes = Salt or Brackish water
  • Not recommended for use in fresh water
    Proven to last longer than zinc due to increased capacity
    Alloy is manufactured to meet or exceed US Military Specification (MIL-A-24779(SH))

Magnesium Alloy Anodes = Fresh water only
  • Not recommended for use in salt or brackish water
    The only alloy proven to protect your boat in fresh water

The price difference between Zinc alloy anodes and the Magnesium alloy anodes is typically close to 2x or more.

I'm also of the understanding that using Zinc Alloy Anodes in fresh water will cause the anode to sacrifice themselves much quicker than the Magnesium alloy anodes. I'm unsure by how much this 'quicker' is but if its 2x then using Zinc Alloy Anodes in fresh water is as cost effective as using the recommended Magnesium alloy anodes but will require more frequent inspection.

What are others thoughts about this ?
 
My boat has the zincs that it came with and after 5 years in clean, fresh water they look pretty much like new. Is this normal?

Phil
 
From my knowledge of how sacrificial anodes work is that if your anodes are as good as new 5 years ago they are not working correctly. I suspect Ranger Tug installed the Zinc Alloy anodes on your boat and as you have kept the boat in fresh water they aren't doing what they are supposed to do.

So is this normal you ask..... well yes if Zinc Alloy anodes are being used which are ineffective. On the other hand, anodes of all kinds are sacrificial and if they've not 'sacrificed' then something is wrong and is not normal.

If in your case, it's not normal then after 5 years it's possible some of the boat's metal has been sacrificed instead.

My advice is to check your thrusters, prop, trim tabs etc for excessive corrosion ASAP.
 
My only comment is that here on the east coast there are times when you are cruising in fresh water. It is my understanding that when you leave fresh water you should wire brush the zincs since they develop a coating that inhibits sacrifice. I wonder what one should do though who is doing the loop and enters fresh waters from the Hudson River all the way down to Mobile, Alabama. I have not really heard of anyone having their zincs changed for this segment of the loop. I am curious what other Ranger owners have done while on the loop.
 
I've been watching the prop, thrusters, trim tabs, etc. and there is no corrosion. The boat is in the water for approx. 6 months of the year.
 
Phil:

Like Mike mentioned.... you might use a fine grit Emery cloth to clean the surfaces of your under water anodes. Anodes can build up surface coatings that inhibit their proper action and in so doing, they don't/cannot protect your boat's metal.
 
My boat has been in salt water for 7+ years and in fresh water for 2 days of that, so I obviously use zinc anodes. I have added a shaft brush and throw a zinc overboard (described below) and on my haul out this past July I had half zinc's left after 13 months. Add in a new marina with new electrical wiring to code, and I'm a happy camper.

One suggestion: in boat yard garbage there are often discarded commercial zincs, the kind that are bolted onto the hull. If you go from fresh to brackish or salt water, put the appropriate zinc on a decent sized wire and hook that wire to you grounding system (alligator clip?) and throw it overboard. One mans garbage.....

There is a metal bar on the aft end of the keel. It is bolted into the hull. It's protection to the keel for those who like to drag bottom. I am aware of one older R25 in my area that has had the bolt heads eaten away on this bar. Check this on boats that don't appear to be using zincs. Mother nature and the laws of physics and electrolysis just keep on working and it's going to eat something. Your job is to get the zinc's eaten, not Ranger supplied parts.

Dave
LOBO
 
Phil:

I want to pass along the advice my previous diver service gave me today. I had asked them what kind of anodes I should be using in fresh water. The diver service has been in business for many years servicing boats in the PNW area.

This was the advice

1) Zinc alloy anodes or Aluminium alloy anodes for fresh water are advised. The diver service prefers the Zinc alloy anodes for fresh water, but both will work.

2) When traversing to salt water from fresh water the Zinc alloy anodes and Aluminum Alloy Anodes should be scraped with emery cloth as the fresh water creates a surface material after 1 to 2 years that stops them from being affective in salt water... and better still, simply replace them with Zinc alloy anodes to be sure your boat's metals are being protected, especially if the Aluminium alloy anodes had been installed for the fresh water.

3) There's no need to opt for the Magnesium Alloy Anodes as they aren't any better and cost more.
 
Thanks to all for the advice......still would like to know why there is no corrosion or deterioration of metal components on my boat. My boat is in an extremely clean, clear water lake, and I don't connect to shore power. Running the engine for moving about and the solar panel keep my batteries topped off. Do these circumstances have an effect?
 
Phil,
The fact that you are not plugged into shore power is making the difference. The major issue with electrolysis is the stray current from poor power supply from the marina or a boat nearby that is defective. However, for the electrolysis to occur you have to be plugged into shore power.
 
The shore power is the main cause for electrolysis. Statistics indicate 90% of electrolysis is caused by connecting to shore power. However, even when not connected to shore power in fresh or salt water electrolysis will still happen, but will be much less.

I quote several articles.... below

"When you connect your underwater metal to the shore power ground you have "bonded" with every other boat on the docks who have the same connection. Now electrolysis currents are free to flow anywhere in the marina and it only takes one boat with a 12 volt DC leakage to eat up every boat within a wide radius even though the offender has zero electrolysis evidence."

Note...
"You could theoretically disconnect the ground connection in the shore power and avoid electrolysis (and in some cases this is a solution) but ABYC regulations require the AC ground be connected to the DC ground so an electrical fault on the boat won't electrocute swimmers in the vicinity."

"Electrolysis only happens when two dissimilar metals are immersed in an electrolyte and connected together. The dissimilar metals have different electrolysis voltages so if you connect them together current flows through the connecting wire one direction and through the water the other. As the current leaves one metal to travel to the other, it causes metal to come off one surface and be deposited on the other like battery plates so the higher voltage metal suffers electrolysis. Electrolysis can also occur when an adjacent structure or boat is injecting DC current into the water and that current goes in one end of your boat and out the other on its way to the destination. This can cause electrolysis even though your boat is not an offender."
 
Some people in the sailing community like to hang a sacrificial anode on a wire over board bonding it with the metal on the boat.

Like it was mentioned before, hooking up to shore is the most common offender of electrolysis. I have been in marinas were I measured something like 60V between my boat and shore ground. Needless to mentioned I was not using that shore power.

Galvanic isolators are the best protection, as long as they don't connect ground to shore. Or if you can avoid it never connect to shore.

however you can occur erosion even if not connected to shore. If there is a voltage differential in the water, or, there are different type of metals that are connected inside the boat and submersed in an electrolyte (aka salt water 🙂 metal will change.
 
Philr

A question- What do your internal engine zincs look like? Are they without "wear" as well?
 
I have a 2013 25sc, about 175 hrs, all freshwater use. Volvo Penta D3-150iG. There are no internal engine zincs. I'm with Phil, I have absolutely no wear on my prop zinc,...three seasons of use. I use shore power 3-4 times a year, most of the time, I'm "on the hook". I use both my generator and solar panel to manage the batteries while in the water. The rest of the time the tug is on a trailer, plugged in at home. Trim tabs and rudder have no zincs. My understanding is that the magnesium alloys are sensitive enough for freshwater, but would quickly sacrifice in brackish and salt environments allowing for no protection in a short time. Zinc works in freshwater, but is not as sensitive as the magnesium, which may be why I don't see any noticeable degradation. I will be checking my generator zinc soon, so I can report back on that at a later time.
As a side note, many of the problems I see on this forum can be directly related to the harsh salt environment. I have to say that because of this, I'm not too keen on introducing my boat to salt water. The Great Lakes are absolutely awesome, along with the Teennesee River and all the freshwater navigation available on the "inside".... Less maintenence= more fun,.. The boating season here is too short to be dealing with unwelcome problems. Love my boat!
Snydzy
 
nzfisher":1gvjldy7 said:
Philr

A question- What do your internal engine zincs look like? Are they without "wear" as well?
Click to expand...

If the R-27 has the Volvo Penta engine then it's my understanding from Andrew that there are no engine zincs to be be concerned with. If it's a Yanmar then it has two zincs. An upper and lower. The upper pretty well stays out of water with the engine not running while the lower one is always immersed. The lower one is the one to check more often. Also, the engine zinc health can be very deceiving. By this I mean, when it's removed it may look visually as being at close to 100%. However, if pinched between thumb and forefinger it will collapse. This is because it has been eaten away on the inside leaving the outer surface untouched.
 
Don't cut yourself short. I love cruising in fresh water also, but the Keys, Bahamas and many areas in the salt water environment are not to be missed.
 
Nzfisher, Haven't checked engine zincs recently.....when I haul out for the winter, I'll check them.
 
Hi guys: Speaking of zincs: can anyone tell me if my Yanmar 3YM30 has engine zincs (plugs)? Rhapsody is a 2009 model and the engine is the original Yanmar fitout from the Ranger factory. I have crawled all over the engine and downloaded the manual from the Yanmar site, but can find no mention of engine zincs (plugs) anywhere. I have been told that the material from which the internal (heat exchanger/water passages) components are made (cupra nickel/bronze?) in these later model engines negates the need for engine zincs. Your thoughts? Regards, Stevan
 
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