galvanic corrosion between chain and shackle - how much of an issue?

[chal]

Following a recent post about chain mooring strops, I've installed a chain secondary. At my local chandlery I picked up a big strong stainless shackle to use with the galvanised chain but the bloke in the shop virtually refused to sell it to me, on the grounds that the two metals would not mix. The galvanised shackle he sold me was a lot cheaper so this was not about making a profit!

I take his point and do my best as a rule to not mix metals, or use anti-corrosion paste where I have to. The latter is not possible in the case of a chain and shackle of course.

The issue is that, while I can use solely galvanised stuff at the boat end of the chain, at the other end it must connect to a stainless steel swivel, so I cannot entirely avoid the problem.

Is it really a problem at all? Most chain is galvanised, and there must be lots of chain out there ending up with stainless shackles.

I necessarily inspect the end of the chain pretty frequently as I disconnect it every time I take the boat out. I can always replace the shackle or saw off the last link in the chain from time to time.

 

[vyv_cox]

Is this for a mooring or anchor? On anchor gear it is not an issue. I probably anchor more than most people in a year, using galvanised chain and stainless steel swivel and shackle. The galvanising goes from about the last three links of the chain after two or three years, so not a big problem.

Use of mixed metals underwater on a mooring is not advised. This is far more difficult to inspect, as you infer.

 

[rob2]

I'd go with that, on an achor you can sort it every couple of years but the corrosion does continue in the anchor well what with all the salt and moisture... On the Hamble there is a ban on using any stainless on moorings - presumably that is based on experience of rapid chain wear exacerbated by corrosion from mixed metals.

Rob.