Anode Material

[ken52]

I noticed that anodes for my outboard(Yam 1999 S150 TXRX) come in different material. They offer Zinc, Aluminun and Magnesium(fresh water only). Is the AL a better choice than the zinc or do they both do the same? I run mostly in salt water.

 

[Chris1956]

Re: Anode Material

I was always told that since zinc was more galvanically active than aluminum, the zinc would protect the aluminum, by corroding away.

My neighbor has a brand new Bravo drive, and was told by the dealer to use aluminum anodes. it doesn't make any sense to me, BTW. We both run in salt water.

I would stick to zinc

 

[ken52]

Re: Anode Material

Thanks Chris seems like most use zink was wondering if the other had a bennifit.

 

[Tim Frank]

Re: Anode Material

Copied from another forum.

"Sterndrives and outboard motors, because of their very active aluminum assembly, are hard to protect.
Initially, the anodes for these units were made of zinc. But corrosion problems in the early 1990s sparked the major engine manufacturers to start selling aluminum alternatives. The increase in protective voltage ensures that the sterndrive is protected. Today, in some cases, using zinc may invalidate an engine's warranty."

 

[Chris1956]

Re: Anode Material

Tim, You are talking about an active anti-corrosion system like MerCathode? What about motors w/o this system?

 

[Tim Frank]

Re: Anode Material

I am talking about sacrificial anodes.
Everything that I have read recently indicates that plain zinc is falling out of favour. Tri-metal Al/Zn/Mg alloys are replacing them.

 

[180Fisherman]

Re: Anode Material

Here is some info I found

Aluminium anodes are often the preferred
choice for pipelines, oil rigs, jetties
and all sizes of hulls in sea water.
They weigh less and provide the same
protection for nearly a quarter as long
again. They also cost less than the
same shaped poured anode in zinc. Slightly
increased driving potential encourages their use
in brackish water, but magnesium should be
used in fresh water.
For an aluminium hull anodes are usually zinc
but with aluminium tabs or inserts see ZHC

Sacrificial anodes are usually
made of special zinc or alu-
minium alloys. For use in fresh
water Magnesium versions are
offered

Zinc anodes
The most common alloy for sacrificial
anodes is over 99% 'special high grade' zinc with
a small addition of aluminium and cadmium
The specification is to MIL-A-18001
It has very low iron and other impurities.

Zinc anodes are suitable for all applications in sea
water but are not effective in fresh water.
Change to Magnesium provided you are not at
sea for more than a week or so in a year.

Zinc is expensive at present but anodes are also available with an alloy that is 95% aluminium. They
are just as effective at sea, slightly more active in
brackish water and can be cheaper as a poured
anode. They are not suitable for fresh water.

For more reading go here www.zincsmart.com

 

[ken52]

Re: Anode Material

Thanks again to all for their suggestions and explainations.