Anchor chain galvanising

[webcraft]

.
How do I know if my anchor chain needs regalvanising?

- W

 

[Rossynant]

By colour?

 

[EdWingfield]

Rust will be showing

 

[webcraft]

But a bit of rust here and there is OK I thought - the remaining galvanising is still working is it not?

- W

 

[MM5AHO]

Galvanizing is a sacrificial coating (bit like hull anodes, but spread thinly). It gets consumed.
Like hull anodes, it protects at some distance, not only the steel thats immediately underneath the zinc. In the case of galvanizing, though typically not such an effective distance. Full protection is often quoted as being to 5mm distance on a pice of steel. In other words a 5mm gap in galvanizing on steel is protected.
The zinc gets progressively thinner with time / erosion. corrosion. When it is gone then rust starts, with the red colour of iron oxide showing.
I suggest that when a chain is about 10% red rust (surface area), its time to re-galvanize.
But a first step is to swap the chain end for end. Typically the part that stays aboard lasts longer. So get the use of both ends, then re-galvanize.

There's several older threads on here about re-galvanizing chain. Some galvanizers are not interested in doing chain as its a bit more fiddly than other steel.

 

[charles_reed]

Galvanizing is a sacrificial coating (bit like hull anodes, but spread thinly). It gets consumed.
Like hull anodes, it protects at some distance, not only the steel thats immediately underneath the zinc. In the case of galvanizing, though typically not such an effective distance. Full protection is often quoted as being to 5mm distance on a pice of steel. In other words a 5mm gap in galvanizing on steel is protected.
The zinc gets progressively thinner with time / erosion. corrosion. When it is gone then rust starts, with the red colour of iron oxide showing.
I suggest that when a chain is about 10% red rust (surface area), its time to re-galvanize.
But a first step is to swap the chain end for end. Typically the part that stays aboard lasts longer. So get the use of both ends, then re-galvanize.

There's several older threads on here about re-galvanizing chain. Some galvanizers are not interested in doing chain as its a bit more fiddly than other steel.

I think it's fair to say that most galvanisers don't like doing chain because it's a lot more fiddly and they really need some specialist equipment.
Couple that with the fact that mosy galvanisers now have a minimum charge @ between 100- 150 kg.
So it's best to form a co-operative to send your chain away for galvanising.
UK galvanised chain lasts about 15 years (of hard use) before showing signs of wear - I've 20 metres which is 22 years old and is showing signs of needing re-galvanising.

 

[SHUG]

The galvaniser needs a proper set-up where the chain can be tumbled before it has cooled. Otherwise you get solid lumps of zinc between the links.

 

[MM5AHO]

The galvaniser needs a proper set-up where the chain can be tumbled before it has cooled. Otherwise you get solid lumps of zinc between the links.

Actually not. It is possible to quite successfully galvanize anchor chain without a centifuge. Admittedly a centrifuge gives a smoother finish, but also a thinner coating. It is possible to make a mess of it too.
Corrosion protection life is directly proportional to coating thickness, so making it thinned means less life.

I have galvanized my own chain twice, and it fits the gypsy OK. (being a galvanizer probably means that I do it more often that necessary)

Yes, most galvanizers are less interested in under 100kg orders, than the tens or hundreds of tonnes in othe orders. But some will do it.
But some who are "yachtie friendly" will do it for a reasonable price. Its available in Scotland.