Trim tab anodes

S

sailor-d

New member
Just an observation from looking in albums and noted that not too many seem to have anodes (zincs) attached to their trim tabs.
The Bennet manual that came with mine specifically recommends installation of zincs on the tab for salt water operation.
I have them on mine and they lose about half their weight over the summer. If one does not have zincs installed - what is being lost and where?

Cheers - Dave
 
sailor-d":fqwpwoyv said:
Just an observation from looking in albums and noted that not too many seem to have anodes (zincs) attached to their trim tabs.
The Bennet manual that came with mine specifically recommends installation of zincs on the tab for salt water operation.
I have them on mine and they lose about half their weight over the summer. If one does not have zincs installed - what is being lost and where?

Cheers - Dave
Click to expand...

If one doesn't have zincs, the next most easily corroded metal in electrical contact with the water based ground oxidizes. How easily a metal is corroded is determined by it's position in the galvanic series which is an intrisic property of the metal. See this link for the position of the metal in the galvanic series. What and where depends on the particulars of your boat but most frequently the mext most easily corroded metal is a piece of aluminum (like the casing on an engine or the lower unit).
 
Thank you for the scholarly reply Roger. I think I prefer the zinc to give its life rather than the lower units of my motors.

Cheers - Dave
 
When I bought my boat it had been in the salt water at Port Angeles inside a boathouse for a year without moving. The tabs had zincs on them, which were 80% gone, and the 304 Stainless tab plates had considerable corrosion. There were several spots with holes all the way through and scarcely any metal left between the holes. Other areas of the plates were pretty much intact, but there was discoloration and rust throughout. The hinges and pins looked fine other than discoloration.

I replaced the tabs three seasons ago with a new set that are also 304 stainless. The boat now sits in fresh-to-brackish water about 5 months a year with frequent trips to salt or near-salt water. I did not put zincs on the new tabs, and they show no sign of corrosion except for discoloration at the hinge pin area. I think if the tabs were constantly in salt I would add the zincs.

I wonder why they don't use the 316 stainless for the tabs. It can't cost all that much more for the little bit of material used to make them. Looking at the excellent reference the Professor provided, I see 316 isn't that much further down the list than 304, but I do know that it takes a whole lot to rust or stain 316 stainless, and not much to do so to 304.
 
TyBoo":22k1xqeo said:
I wonder why they don't use the 316 stainless for the tabs. It can't cost all that much more for the little bit of material used to make them..
Click to expand...
Good question. Most trim tabs do not require any significant machining in manufacture, so that is probably not it. My guess is that it is marketing: "stainless" is the magic word when it comes to selling a metallic part to an end user.
 
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