How Fast Will it Rust ?

[settingsun]

My well-intentioned but impatient husband decided to forego all help getting our brand new 300' of 5/16 HT Acco chain from our truck to our boat, and dragged it 800' from the bed of the truck down the ramp and along our concrete docks. By the time it was loaded into the anchor locker of our boat, a bunch of the galvanizing had been scraped off, totally exposing a half-inch strip of shiny steel on almost every link of the chain.

I have two questions:

1. Once we start cruising in August, anchoring out every night, how fast is this chain going to rust? Or would it have gotten equally scraped up in the first few months of anchoring anyways?

2. Is there anything we can do to treat the chain? A BoatUS article by Tom Neale describes coating the chain with 6 coats of "Starbrite Corrosion Protection" but I could not find a product with that name in Starbrite's online catalog.

[MarkJ]

I would take it and have it regalvanised.
They are in big heavy industraial suberbs miles from town, but its quite cheap. Load the chain into the car trunk and drive into the place. Often you pull up next to all the work trucks etc Nicolle found it quite fun to be gawked at by all these 'rough trade' workers.

While the chain is still new it won't need a pre treament so it will be a cheap job, maybe $100 or so and be done in 2 or 3 days.

Then you will be anle to sleep easy!

The ungalvanised chain will rust very quickly as it sits in a damp wet locker.

[James S]

I respectfully disagree... our chain has several areas that have lost the galv. and has no more than surface rust.
It could have to do with the climate in the locker, or the frequency of deployment...dont know, but I wouldn't loose any sleep over it.

[tager]

I would just use it and see what happens. You could paint it with cold galvanize. It certainly couldn't hurt.

[klem]

Why exactly are you worried about rust? Are you worried about chain strength or do you not like handling rusty chain and the associated mess? If you are worried about the strength, most people who are weekend cruisers won't anchor enough to have the rust really compromise the strength. However, if you don't like getting rust on everything, then you might want to do something.

Galvanizing will naturally wear off from use anyways. Links don't tend to wear out where you have lost your galvanizing, they tend to wear out where they contact the next link. This means that he probably did not shorten the life of the chain noticeably, just made it much messier.

[Eleven]

If it's been properly hot dip galvanised then the zinc is chemically involved with the surface of the steel. The zinc will also migrate by electrolysis to any unprotected areas.
Keep an eye on it but I doubt you'll need to get it re-done.
Electro-plating is less likely to weld all the links together and there are many more places around that can do it. The pre-treatment is usually necessary on visible rust and this is an acid bath. A good hose wash and a wire brush for a few patches may mean you avoid that extra process.
It takes a lot to destroy good galvanising but sea water is one of the things that destroy everything but plastic shopping bags, bottles and their tops.

[thinwater]

Corrosion engineering is a part of my job, so a few thoughts:

Klem nailed it: only the area where the links meet will matter. The zinc is ALWAYS rubbed off there.

Eleven had good points, but I believe missed the theory a bit. There is no surface interaction. However, galvanizing does protect electrochemically from a distance, just as dissimilar metals can cause corrosion a distance away. It is about the flow of electrolytic currents. The beauty of a zinc coating is that it is not harmed by small gaps, the reason it is still the state of art for chain.

Electroplating is very thin and is probably a waste of money for chain. The coating is far too thin for any marine application. Not even very good for a hinge on the garden gate.

Paint or any other coating. A bad idea that will actually makes it worse. Uncoated chain spreads the electric current over its full surface; after painting on the chipped areas corrode and the damage is concentrated there... between the links.

I doubt you have lost as much zinc as you think and I doubt you have shortened the life of the chain more than 10%. You have NOT made it unsafe, as the important damage is between the links. The money would be better spent on a new chain 10 years from now.

[Eleven]

Your comments accepted, deepwater. I've done a good bit of structural design and installation. Hot Zinc Plating is really good and does tend to fix scratches and damage itself.
The electro-plating was intended to assist in that repairing action if in fact the chain starts to show signs of rust in the next few days.
Certainly the long term failure mode is, as you suggested, in the heavy wear area where the links work on it's neighbour under tension.

[thinwater]

Originally Posted by Eleven

Your comments accepted, deepwater. I've done a good bit of structural design and installation. Hot Zinc Plating is really good and does tend to fix scratches and damage itself.
The electro-plating was intended to assist in that repairing action if in fact the chain starts to show signs of rust in the next few days.
Certainly the long term failure mode is, as you suggested, in the heavy wear area where the links work on it's neighbour under tension.

Agreed. Electroplating might be a cosmetic fix. I'm never interested in cosmetics, so I dismissed it too quickly.