Yachts are only rarely built out of galvanised steel. I'm not entirely sure why, but suspect it has to do with the extra weight of the material compared with mild steel. It would still need a protective paint coating underwater. If left bare then in salt water the zinc would tend to disappear fairly quickly with electrolysis, and the steel would then be as susceptible as mild steel.
Of course, galvanised steel is regularly used for the above-water fittings of converted workboats.
I remember reading somewhere that galvanising chain is not neccesarily a good decision economically as it is expensive (a good percentage of the cost of the chain) and is often not done to a good standard.
Galv is a sacrificial coating ie it erodes away in use. So its life depends on thickness and the rate of erosion.
I was going to give you a long technical reply about how the thickness varies greatly and the erosion does too - but in the end, the answer to your question is "how long is a piece of string?"
<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.
You can get them regalvanised, but it is expensive as it's based on weight and quantity. Try getting several owners to get all their anchors etc for galvanising together and send off as one 'order'. This is what I did several years ago. Make sure you ask for galvanising to marine standards - there is/was a BS standard for this but don't know what no it is.
Don't bother with the zinc based paints - it'll come off after a couple of anchorings.
<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif
If using galvanised sheet, the welding will boil off the galvanising and poison the welder.
If hot dip galvanising, it'll have to be done after the build, and you'll have a real problem not distorting the boat with the heat and the weight of ballast necessary to counteract the bouyancy in molten zinc. Not to mention the size of tank necessary to do it in!
I enquired about having my car's body shell hot dipped, only to be told that the probability of severe distortion was too high for the company's insurer to permit them to do it.
There is now a system of cold galvanising available which is applied to shot blasted surfaces.
Has a good pedigree from the offshore and naval markets. Can be easily touched up, multi coated and no warping problems from the hot dip process. About the same price as hot dip.
Check with your local galvanising sources - should be some will offer as an alternative.
I'm quite sure I've seen a least one advert for a galvanised yacht, a fairly recent one from memory which was a lifeboat conversion. Perhaps it was rivetted!