Recycling zinc anodes

[CDK]

Well, you are not actually protecting them unless they are connected with a cable to your hull, but they certainly create a few millivolts and these keep nibbling at your anodes until there is nothing left.

If the hull has no aluminum parts in the water you could use Al anodes and save a few $$, but zinc protects better because the voltage potential is higher. The conductivity of the water also plays a role.

Originally Posted by wildman

The second thing was that on haul out I found most of my anodes corroded more or less equally except for two both on the stbd side. Two mounted in a similar location but on the port side were in need of replacing. These two were the same make/size as the stbd side two. The port side lies along side an unpowered dock while the stbd is some 6 metres from the next dock. The dock is held up by rusting steel pylons - am I protecting the landlord's (docklord's??) pylons?

There is something positive in this case! You have the proof they work correctly, sacrificing themselves!

Well said Cornelis!

Regards
Richard

[CDK]

A quick addendum because I was distracted and didn't finish the reasoning.

Taking stainless steel as a reference, the potential between ss and aluminum is approx. -.2 Volts, zinc gives over -1 Volt, so it is much more active. To obtain the same level of protection you would need 5 times the number or size Al electrodes, so cheap turns out to be expensive!

In clean, low conductivity water you could use Al because corrosion rate is low, in distilled water you need nothing at all.

Thanks Richard. I'll try not to get overconfident.

Up here, one used to be able to find aluminum everywhere for free (scrap) and it made sense. They are both expensive now ($1 lb.) but two savings are that, if you can get zinc without too much shipping cost, it will be far cheaper than buying zincs (Alaska/Hawaii, etc., more so), and people throw out slightly used zincs all the time.

[hoytedow]

A little more caveat on zinc smelter: http://chestjournal.chestpubs.org/co...3/862.full.pdf

[Landlubber]

..stick with the zincs, you already have them anyhow....

[LyndonJ]

There's some good reading here too

blisters around zincs on steel boat

Wow, Hoyt - ought not breath it!