Galvanized and Stainless components

I'm becoming more aware of how common it is to have a mix of galvanized and stainless components being used to create an anchor rode. Chains are usually galvanized but occasionally are stainless, swivels are almost always stainless, anchors can be either, as can shackles. I've seen all kinds of combinations of these components seemingly used without consideration that stainless and galvanized steel are far apart on the galvanic chart. Even boat manufacturers will add a shiny stainless anchor on the bow connected to galvanized chain. Of course I know that price is a big consideration, but am I wrong in thinking that using this mix of metals is not the smartest thing to do?

backinblue said:

I'm becoming more aware of how common it is to have a mix of galvanized and stainless components being used to create an anchor rode. Chains are usually galvanized but occasionally are stainless, swivels are almost always stainless, anchors can be either, as can shackles. I've seen all kinds of combinations of these components seemingly used without consideration that stainless and galvanized steel are far apart on the galvanic chart. Even boat manufacturers will add a shiny stainless anchor on the bow connected to galvanized chain. Of course I know that price is a big consideration, but am I wrong in thinking that using this mix of metals is not the smartest thing to do?

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Doesn't seem to be a problem, probably because the zinc in the galvanizing is sacrificial to everything else. So it ends up being a tradeoff between strength, shininess, and cost.

twistedtree said:

Doesn't seem to be a problem, probably because the zinc in the galvanizing is sacrificial to everything else. So it ends up being a tradeoff between strength, shininess, and cost.

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True enough. Zinc goes away first, then the underlying steel. Not sure I would want that happening to my galvanized anchor or chain connected together by a stainless swivel, yet many people do it. Maybe I'm being too anal about my ground tackle.

For chain and shackles SS has less tensile strength thus a lower WLL than good steel components of comparable size. First Chain Supply has good data and tables showing these relationships.

Be careful with quality chain and fittings from lower priced outlets. I prefer ACCO chain and forged heat treated shackles.

A friend using a HydroBubble anchor attached a zinc to his (cannot remember where/ chain or anchor) and said that worked in an active river. He did not stay there longterm so just throwing that out there. Is there any reason why a zinc would (or would not) be useful?

I know over zincing can create problems on boats, so I'm curious what the experts have to say...

I have never had an issue with it. If you anchor full time maybe it would be something to worry about.

sunchaser said:

For chain and shackles SS has less tensile strength thus a lower WLL than good steel components of comparable size. First Chain Supply has good data and tables showing these relationships.

Be careful with quality chain and fittings from lower priced outlets. I prefer ACCO chain and forged heat treated shackles.

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I agree it's worth paying for quality chain and components. That said, I don't agree that all galvanized chain is stronger than all stainless chain of the same size. Different qualities, alloys, and strengths are available for each.

Comodave said:

I have never had an issue with it. If you anchor full time maybe it would be something to worry about.

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I don't believe there is much of a corrosion issue with it because it doesn't spend that much time in the water. On the other hand, I use exclusively galvanized steel in chain and shackle, because the strength of stainless under load is always in question. Not recommended for shackles, only high test steel is recommended.

Of course, if you never load it, you'll never test it. Ideally your anchor, shackle, and chain will be under working load roughly compatible.

"I agree it's worth paying for quality chain and components. That said, I don't agree that all galvanized chain is stronger than all stainless chain of the same size. Different qualities, alloys, and strengths are available for each."

SS can suffer from crevice corrosion which can be invisible until the SS fails.

Lots easier to see rusting long before the part fails.

Thanks FF, I have ben reading and learning more about the pros/cons of SS chain and you are correct. My original point which still puzzles me a little is the mixing of different metals with very different galvanic properties but nobody puts any thought into it. People are fanatic about not using ss screws in aluminum even if they are not underwater for example. I think I've come to the conclusion that the corrosion risk is smaller than I imagined and also that for the person who anchors occasionally, ss chain, if properly sourced, will perform fine for a long time.

In this day and age of cost cutting measures the suggestion to stay with a highly reputable mfg'r is the best. Some metals marketed as Stainless Steel can be 302, 304 or 316 (big difference in salt water environments). The common man would never know the difference. Some SS components are not passivated or electropolished which improves the
corrosion resistance by dissolving free iron on the surface only.

Forged items are usually much stronger than cast or wrought. There are many different quality levels of Galvanizing, although the term is used quite frequently and assumed to all be the same, WRONG.
I have also seen material certification documents forged in low cost regions in China.
I will stay with my Hot Dipped Galvanized ACCO chain with Forged shackles. Don't forget the seizing wire !
I also inspect my ground tackle frequently for corrosion.

In order for galvanic corrosion to occur, the dissimilar metals need to be in GOOD electrical contact with each other AND immersed in an electrolyte. I have a strong feeling that there aren't many examples of issues with mixed SS and galvanized chain parts because there is not a good, low resistance contact between the dissimilar parts.


Ken

kchace said:

In order for galvanic corrosion to occur, the dissimilar metals need to be in GOOD electrical contact with each other AND immersed in an electrolyte. I have a strong feeling that there aren't many examples of issues with mixed SS and galvanized chain parts because there is not a good, low resistance contact between the dissimilar parts.


Ken

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Hi Ken,

I agree with what you are saying, but wouldn't an anchor rode under tension in salt water meet all those requirements? Granted for most of us, that is a very small percentage of the time.

backinblue said:

Hi Ken,

I agree with what you are saying, but wouldn't an anchor rode under tension in salt water meet all those requirements? Granted for most of us, that is a very small percentage of the time.

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Good question, maybe but it doesn't take much to interfere with a good connection. For example, if I wanted to test the conductivity of something galvanized, even using fairly sharp probe tips one usually has to work them into the surface to get a reasonable connection. So 2 rounded surfaces with other possible crap in the way? Probably hard to get a good connection. But as you say, most anchors spend most of their lives out of the water anyway.


Ken

kchace said:

Good question, maybe but it doesn't take much to interfere with a good connection. For example, if I wanted to test the conductivity of something galvanized, even using fairly sharp probe tips one usually has to work them into the surface to get a reasonable connection. So 2 rounded surfaces with other possible crap in the way? Probably hard to get a good connection. But as you say, most anchors spend most of their lives out of the water anyway.


Ken

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Thanks Ken, I appreciate your feedback. For the record I was an electronic technician and an EE so I know what you are saying. In my mind, a chain under tension has pretty good electrical connection between links and is also, in my case immersed in saltwater so there is likely a galvanic reaction. I'm kind of surprised it's not more of a concern, but again I am probably overthinking it (we engineers often do that).

SOOOOO.... here's my whole story if anyone cares. I bought a used boat 3 years ago with a marginal (in my mind) danforth-type anchor and 50' of chain and 200' nylon brait. I soon upgraded the anchor to a stainless Ultra and swivel. Love them both btw. After a couple years, I noticed a little corrosion at the junction of the chain and swivel and became aware of the galvanic issue. Maybe I over-reacted, but I since have purchased a new rode with SS chain (Suncor HT Domestic 316L) and new nylon brait. The old chain was of unknown quality/strength, and the nylon looked a little ratty anyway. So that's what's got me into this discussion, probably more of my stupid brain over-thinking things.