Anchor Chain Corrosion

[wsmurdoch]

Let's see.

I bolt inch thick bits of zinc to the bottom of my boat and connect them to the boat's grounding system to protect the underwater bronze, and I am happy when they corrode away. I cover my anchor chain (which is connected to the boat's ground through the windlass or the stem fitting) with a few 1/1000 of an inch of zinc, and I am unhappy when it corrodes away.

I wish I could get galvanic corrosion devils to attack the right zinc.

[Hard Rock Candy]

The first time I went to Belize I had a 25 ft Macgregor. I was also very low on money and I had an old rusty anchor and chain that I had been given. When I anchored outside Belize city I put that rusty anchor down and went to bed. In the morning, I pulled it up and there was absolutely no rust on the anchor or chain. they both looked like they had been sandblasted. every rust pit showed. I thought about bottling the stuff and starting a business right there.


Mac

[colemj]

Originally Posted by a64pilot

I've read that Teflon is toxic, but as it's used inside of the human body and on cooking surfaces, that doesn't seem to make much sense?

Teflon itself is inert. If it is burned, the fluorocarbon gases can be toxic, but I think you need pretty high temperatures for this to happen (>250C/500F?).

Mark

[Jim Cate]

Teflon would not be a toxic hazard, but it would not work well as a coating for chain.

First, getting it to stick to the links would be a non-trivial task. Second, it would immediately be crushed and stripped off where the links bear upon one another as load came onto the chain. The inter-link pressures are quite high in the small contact areas between links, and Teflon is pretty soft. Then, of course, you would have wear where it goes through the gypsy, grinds over the bow roller, is dragged over rocks and gravel and coral and suffers the various indignities that anchor chain must routinely survive.

Nope, not a player...

Jim

[MVNightWatch]

Originally Posted by a64pilot

I think the "white rust" is zinc oxide, and the best and longest lasting coating is zinc (galvanizing)

I've read that Teflon is toxic, but as it's used inside of the human body and on cooking surfaces, that doesn't seem to make much sense?

Are you saying the oxidized portions are now more resistant to further oxidation? There's a Picasso statue and a building in Chicago's Daley Plaza that use the same concept on their ferrous metals.

[transmitterdan]

Originally Posted by MVNightWatch

Are you saying the oxidized portions are now more resistant to further oxidation? There's a Picasso statue and a building in Chicago's Daley Plaza that use the same concept on their ferrous metals.

I don't think so. Zinc oxide is a white powder and does not stick to the surface very tenaciously thus is easily rubbed off. One of the attributes of zinc on chain is that its oxide isn't red and doesn't stain like iron oxide. Another is zinc blocks oxygen getting to the underlying steel until the zinc is dissolved, worn off or displaced by galvanic processes. Once the zinc is penetrated then oxidation of the underlying steel can commence. Sometimes without visual cues.

[a64pilot]

Originally Posted by MVNightWatch

Are you saying the oxidized portions are now more resistant to further oxidation? There's a Picasso statue and a building in Chicago's Daley Plaza that use the same concept on their ferrous metals.

No, just rendering an opinion of what I thought the "white rust" was

[Snowpetrel]

From the pics it doesnt look to bad yet... hard to tell but sometime galv can go a slightly rusty color and still be fine for many years, other times it is a sign the gal is getting thin and is past its best. Any idea what caused it, could that section of chain have been left sitting in a pool of water trapped in the bottom of your chain locker? I would try a watch and monitor approach, and if it seems the rust is getting worse maybe try some cold gal paint on the worse sections to eek out more life from the chain. Also regular washing with fresh water will extend the life of the remaining galvanising. Make sure nothing stainless or bronze touches the chain anywhere (except the gypsy), and raise it off the bottom of the locker on plastic gratings to help it dry.

Sent from my GT-P5210 using Cruisers Sailing Forum mobile app

[mf70]

Thanks for the photo. My first thought was, "Hmm, he doesn't use his anchor enough!"

Where are you anchoring? What kind of bottom do you usually have?

In the Chesapeake, we usually have mud. I have had pretty good results with zinc paint. It lasts ~2 years or so. The mud is non-abrasive, but can be chemically active, leaving exposed iron black. It is not necessary to have 100% zinc coverage. Like a sacrificial anode, any nearby zink will protect "its" iron.

[zeehag]

original poster-i covet your chain. it looks awesome good. mine lost galvo in la cruz anchorage in the rocky bottom and zihuatenejo in the rocky bottom.... yours is awesome good looking.