Trojan Boat Forum

The Dog House wrote:The anode websites list magnesium for fresh water, aluminum for brackish water, and zinc for salt water. This would imply that aluminum is between magnesium and zinc. In my personal experience, the aluminum anodes corrode faster than the zinc anodes. Is it possible the anode companies are using a different aluminum alloy?

I made a change to the list above. I did some digging and realized I omitted something. There is the aluminum that components are made of; hulls, stern drives etc. and the aluminum alloy that anodes are made from. So that changes things somewhat, thanks for catching that. Still trying to figure out the figures you got off the net. Traditionally I see negative numbers as anodes are the negative charge (anode) in the equation and the item being protected is more positively charged (cathode) in comparison.

The reason for aluminum in brackish water and magnesium in fresh is that these waters are less conductive than salt water and therefore require a higher driving potential. So a greater voltage difference is needed between the anode metal and the metal being protected. Thus these metals protect better in those waters than zinc. Put magnesium in salt water which is very conductive and you`ll be lucky if it lasts a week!

PS. Jeff, regular aliminum won`t do. It`s a special alloy that contains other metals, otherwise it would be like putting a piece of regular aluminum on an aluminum drive....no protection there.

Well darn you, what kind of a chemist are you sorry but I thought it was funny

jefflaw35 wrote:Well darn you, what kind of a chemist are you sorry but I thought it was funny

Getting to be a too old to remember numbers anymore chemist

Darn I knew it

Big D wrote: Still trying to figure out the figures you got off the net. Traditionally I see negative numbers as anodes are the negative charge (anode) in the equation and the item being protected is more positively charged (cathode) in comparison.

It may just be a current versus electron flow situation. Current travels in the opposite direction of electron flow because Ben Franklin guessed wrong.

The Dog House wrote:It may just be a current versus electron flow situation. Current travels in the opposite direction of electron flow because Ben Franklin guessed wrong.

Good enough for me, I'll take that ....Ben's fault

just looked at the boat. two on the prop shaft, one on the rudder and zero on the trim tabs. trim tabs are painted with bottom paint and where the paint chipped off it looks like aluminum or polished stainless. there are also no sign of anodes ever being on the trim tabs. The boat will be in salt water all summer.