Galvanising

Neeves

Well-known member
Joined
20 Nov 2011
Messages
12,578
Location
Sydney, Australia.
Visit site
I wondered what people thought of galvanising quality currently.

We all carry galvanised product, primarily chain and anchors (but also shackles (though maybe they are special case and might be omitted). But most common chain in Europe now comes from China, excepting some from Italy, is Germany still a source? Americans still have a vibrant industry for anchor chain, as does Australia. Our anchors come from an even more varied source, a lot from China, the UK (I'm not sure where the Knox is galvanised), Spade in Tunisia, Manson in New Zealand, Anchor Right in Australia. Toe Down in America, CQR in Scotland. Is there any difference with the quality of galvanisng - are some sources better than others?

Can we tell the difference? Has galvanising got better or worse, again can we tell the difference.

Jonathan
 

MM5AHO

Well-known member
Joined
1 Oct 2007
Messages
2,517
Location
Central Scotland
Visit site
As an operator of 2 galvanizing plants, I'll be really interested in the replies to this. I'll hold comment until there are some replies.
 

rogerthebodger

Well-known member
Joined
3 Nov 2001
Messages
12,627
Visit site
When I lived in Birmingham UK and building my first boat that had a lot of galvanised fittings I was told by my friendly galvaniser that the temperature of the zinc bath effects the thickness of resulting coating so I always tried to have my job done at the start or end of the day when the bath was not up to full temperature or was cooling down after the heat was turned off.

The higher temperature an thus thinner coating results less zinc being used and saving the galvaniser money.

May be MM5AHO can comment.
 

Neeves

Well-known member
Joined
20 Nov 2011
Messages
12,578
Location
Sydney, Australia.
Visit site
To contribute to my own thread:

I did some testing - simple stuff, I cut off short lengths of chain, put them on a long piece of galvanisied reinforcing rod equidistant apart, suspended the rod and then let them abrade over the seabed, primarily silica sand.

The best abrasion resistance was from American chain makers, both Campbell and Peerless (who own the ACCO brand). I tested Imperial chain but I see no reason why ACCO/Peerless metric chain would be any different. Peerless and Campbell G30 was almost a G40 strength, their G43 exceeeded specifications but their G70 strength only just met specification. The Americans have a specification for extension to break - they invariably did not meet the specification - American chain tends to be brittle - though this is not in any way reflected in performance - no-one complains. Campbell only make imperial sizes, but if that's what you need - its good and a recommended buy. Both manufacturers had very good abrasion resistance across their range, it varied - but if you want reliability - buy American for strength and galvanising

Maggi chain is strong, and extends and meets the American specification. It tends to be stronger than comparable brands, so therir G40 is good and their G70 stronger than Peerless or Campbell. An side, strength of chain, particualryl G70 is very good but small metric links are very difficult to to allow compatibly strong connectors. Maggi's galvansing, which is subcontracted, is poor - the coating is thick enough but it is brittle and flakes. This seems to be reflected in user's comments who complain that gal life is short.

PWB Australian chain G30, obscurely called Grade L, is strong enough, but not as strong as G30 from CMP, American or Maggi, and the galvanising (again subcontracted), life, is poor. It easily meets American standards of extension to break. There are 2 manufacturers, PWB and Serafini. I would not touch the latter.

Chinese chain galvanising is variable. One unbranded source was exceptionally strong. better than a G43, and had excellent galvanising (as good as the Americans). CMP chain is strong, I only tested a G30, but it was almost a G43 strength. Galvanising was thick enough but subject to flaking. I have heard no user feedback (CMP with chain are relatively new here). Another piece of unbranded chain from China was weak and had poor galvaniising.

Of anchors, I can only comment objectively on 3 sources. My genuine CQRs have excellent galvanising. My Anchor Right Excel, subcontract galvansing has lasted better than the PWB chain. My Manson Plough galvanising has been good. I do see other anchors that look questionable - but I simply do not know how they have been used - so I reserve judgment, except to say the early Rocnas, made in NZ look a bit tired now - but they might be well used and they are almost 10 years old now. The galvanising on my Knox looks very good - but looks are totally meaningless!

Conclusions

If I was buying chain, and ignoring cost, I would buy metric chain from Peerless, it meets specification (apart from extension to break) and has the best galvanising of anything I have seen. But then they galvanise in house and only make chain - so they ought to have got it right by now!

I would not touch Maggi chain - the life of the galvanising looks very questionable, no better than most Chinese.

For Australians we have little choice both CMP and PWB galvanising is inadequate - possibly buy CMP because its stronger (and though I said ignoring cost - its also cheaper.)

Buying Chinese chain is a lottery, most exceeds strength and is very good, but there is the occasional supply that does not meet specification. It is unmarked so you never know what it is you are getting. Galvanisning is even more of a lottery - some of it is good but most poor and subject to flaking.

Geoff will correct me:

A fresh galvanising bath is better than an old one, that will contain Fe (or other deleterious elements?) in the bath. So even a good galvaniser will have variable quality. Galvanisers are commonly sub-contractors who coat 'engineering' products whose application seldom involves heavy abrasion. Consequently the fact a coating flakes is not so important, for engineering products. Equally a thin coating is not that deleterious as most engineering product simply sits out in the rain and last a very long time. (We have a galvanised steel platform that I installed 18 years ago. It looks like new. We have a galvanised steel walkway under and round a swimming pool, its maybe 30 years old, we live within 150m of the sea - it looks, dusty, but no corrosion). Chain is a very small part of a galvanisers production, they focus on engineering components and possibly have no idea that abrasion is the main issue - so consequently a coating that is abrasion resistant is not a priority. Galvanising quality varies from individual operators, as with any industrial process, if you can find one that is sympathetic to the marine environment or specialises (in chain) there galvanising ought be better. it would be impossible to visit a chandler and pick a chain off the shelf and know it has good coating.

Jonathan
 
Last edited:

Neeves

Well-known member
Joined
20 Nov 2011
Messages
12,578
Location
Sydney, Australia.
Visit site
The galvanising on a chain is more abrasion resistant than the chain (even G70 chain) - so as soon as you loose the coating, from abrasion, the underlying steel will wear more quickly than did the coating. If the chain flakes - then you are not enjoying the abrasion resistance the coating offers.

TQA - I do not know enough about it but I am surprised that wear was sufficient to cause the chain to jump in the windlass. Wear would be on the 'long' of the link or 'inside' the crown and I thought the critical dimension was length (so outside the crown), not width (I stand to be corrected). Are you sure your chain had not been stretched - it is unlikely, but possible.

I only measured steel abrasion on G70 and G80 and G40 would be faster - but good gal abraded much less than the underlying steel

Jonathan

edit I've thought about that - yes if abrade inside the crown the links will be longer (at the gypsy) - so yes possible and logical, close edit
 
Last edited:

vyv_cox

Well-known member
Joined
16 May 2001
Messages
25,563
Location
France, sailing Aegean Sea.
coxeng.co.uk
My chain in Greece was bought in Corsica and I suspect that it may well have been Maggi. Within three years the galvanising was in very poor condition, despite the chain having been reversed, with plenty of red rust visible throughout. I brought the chain home and had it regalvanised at BE Wedge. That was in 2008-9 I think, since when there is no deterioration in the galvanising. It lost its brightness quite quickly of course and has a small amount of white 'zinc rust' on it but absolutely no sign of steel corrosion.
 

MM5AHO

Well-known member
Joined
1 Oct 2007
Messages
2,517
Location
Central Scotland
Visit site
Not too many replies on this one, but I'll try to give something useful.
Galvanizing as a process is far LESS in the control of the galvanizer than might be imagined. The old saying that "You can't make a silk purse out of a sows ear" comes to mind, but the fact is that most don't know what they do with their steel that has a huge impact on the outcome of galvanizing. Such things as the chemistry of the steel, the design and fabrication of the item, and the condition of the surface of the steel are all out of the control of the galvanizer, but have huge impact on the result.
It's true that a "clean" galvanizing melt of zinc is important. Galvanizing is the formation of iron-zinc alloy on the surface of the steel rather than a coating of zinc. Iron and zinc mix together to make an alloy, so any free Fe in the molten zinc forms that alloy in minute particles called "Dross" that can float about like sand, and give rise to gritty surfaces. That's partly in the control of the galvanizers, but some fabricators make that quite difficult. Leaving drillings, swarf, grinding dust, sawing swarf etc all causes problems.
There's a standard for galvanizing, (ISO1461) and most galvanizers operate to that, but most customer's don't know what it says, nor do they demand adherence when they should.
The are sometimes reports of galvanizing "flaking" off. This is rare, but can happen and is usually the result of the chemistry of the steel, mostly the Si and P in it. Galvanizing a second time has consumed some of the Si near the surface, so a different result next time can happen.
The life expectancy of galvanizing varies greatly with environment. In the UK up to 175 years can be had in rural environments. In marine splash zine situations the same item coated the same way could last 10 years. The life is directly proportional to thickness of zinc / zinc alloy, so up to a point the thicker the better. But not too thick! Thickness at about 400um or more (0.4mm) can be problematic where the coating can become brittle and flake off.
There's no difference in protection between shiney bright and dull grey. What causes that is the steel chemistry.
Galvanized steel has increased abrasion resistance. The alloy formed is harder than mild steel. But the upper layer of pure zinc is softer.
The temperature of the galv bath doesn't vary much, and stories about getting things done on Monday morning etc are probably myths. Ours run at 445C +/- 2C. Most are similar. I know of no-one who "turns theirs down" overnight or the weekend. Its far better to install better insulation for non-production periods. The zinc erodes the kettle that contains it (slowly dissolves its container, turning it to alloy), and that rate is dependent on temperature. 450C is the acknowledged "sweetpoint". Its possible to galv hotter, even to 550C, but the kettle will last perhaps a month compared to 10 years!! I know this personally!! A new kettle is very expensive, about half the price of a new house. No one turns the heat off totally, that leads to a disaster. Freezing point is only 419C, so it doesn't take long to freeze, and can take a week to melt it out again, that can't be rushed.

The coating thickness is affected by temperature, but its not straightforward. Hotter means faster alloying reaction so thicker coating, while at the same time hotter = thinner more fluid and that leads to thinner coatings. In practice not much difference the two cancelling each other out.

Comments any use?
 

Neeves

Well-known member
Joined
20 Nov 2011
Messages
12,578
Location
Sydney, Australia.
Visit site
Great answer Geoff,

You are correct it appears galvanising is not the subject that excites most of us (or not until our chain starts rusting quickly!).

There is a suggestion, an idea to which I do not subscribe, that the strict environmental restrictions that are put on galvanisers in 'Western' or developed countries has resulted in a reduction in the 'quality' or level of galvanising protection. Specifically it was suggested that Oz and New Zealand galvanisers were particularly poor (because, possibly, of these environmental restrictions).

I'm of the view, having looked at chain from America, Europe, Australia and China that their are variations in the quality of the product from individual galvanisers in one country much greater than the variation in quality between countries. However some suppliers do tend to supply product more prone to flaking than others, see below.

Would you care to comment?

I do suspect that sub-contract galvanisers do tend to treat chain the same way as a steel beam and simply coat with a minimum of coating - when in fact a thicker coating would last longer. This is possibly not the fault of the galvaniser but the chain maker (or whoever might be having the product coated - for example an anchor maker) who does not specifiy nor check that he gets what we, the end cusotmer, might want. Having said that, as evidenced by the interest in the thread, most do not know what they want!)

Vyv has a simple test to look at the adhesion of the galvanised coating which he developed from a British standard. He suggests cutting one side of a chain link and bending it through 180 degrees such that you form an 'S'. If the gal flakes off the coating is poor. The same effect can be seen when you test chain to failure - the gal on some chain can be seen to flake off on other chain the gal stretches with the underlying steel and remains adhered. You suggest gal flaking is not common, I'd beg to differ and say that using Vyv's test, or looking at broken chain, there are significant visual differences in coating adhesion (and I might highlight the Americans for having got it right). The tests might be a bit harsh for many gal steel applications, steel beams on a bridge are never going to suffer the stresses imposed in the test - but anchor chain is subject to harsh treatment. The gypsy and bow roller (if a metal roller) and certainly the seabed are hard masters and any gal subject to flaking might have shorter lifespan.

Do you galvanise anchor chain and if you do so, do you treat it differently from the normal engineering product you would commonly coat?

Jonathan
 

crewman

Active member
Joined
30 Dec 2008
Messages
820
Location
Edinburgh
Visit site
Thank you, information from someone who really understands a complex process is always interesting. You say that regalvanising can have different result than the initial treatment. Does this make the result harder wearing or less durable?
 

Tradewinds

Well-known member
Joined
12 Jan 2003
Messages
4,042
Location
Suffolk
www.laurelberrystudio.com
Great answer Geoff,

You are correct it appears galvanising is not the subject that excites most of us (or not until our chain starts rusting quickly!).

You suggest gal flaking is not common, I'd beg to differ and say that using Vyv's test, or looking at broken chain, there are significant visual differences in coating adhesion (and I might highlight the Americans for having got it right).
Jonathan,

Some criticism of ACCO chain re galvanising here (2013 post). They seem to suggest earlier (pre Peerless) chain was better quality. Some even preferred Maggi's quality.

http://www.cruisersforum.com/forums...er-cruisers-experiencing-problems-108186.html
 

Neeves

Well-known member
Joined
20 Nov 2011
Messages
12,578
Location
Sydney, Australia.
Visit site
Tradewinds,

Good link, useful information, thanks. :)

Maggi appears to be questioned currently, there are a couple of current comments - one on this thread. Hopefully ACCO or Peerless lifted their game, current quality, or quality in 2014 seems acceptable. Hopefully manufacturers, or at least Peerless and Maggi, read these threads, take note and appreciate we are trying to monitor!

One problem with galvanising is that it takes so long for comments to appear. A complaint in 2013 might refer to 2009, or 2011, production. Its not implicit in Geoff's post but if bath chemistry changes with usage or time then a batch of chain at one part of the cycle might be excellent and another batch more questionable. So buy today and quality could be good, buy in the New year and it might be less so - ??

Interestingly 'we' test antifouling (and every generation of electronics (so every 6 months :() with amazing regularity but galvanising is left to languish. If we had more regular and more widespread tests we might have a better picture.

Sadly the interest in this thread possibly reflects the same interest of publishers - so I'm not optimistic :(

Jonathan

edit: Crewman raises the question but one factor that has struck me is that people who re-galvanise suggest 'their' galvanising is better than the original. Whether this is an objective comment and accurate after time I do not know (people only comment when they look at their freshly coated chain not 4 years later). But it might be if you re-galvanise the sub-contractor takes greater pains to get it right, or the second time the coatings is better (because for some reason a second coat is actually 'better' on a previously coated substrate?).

close edit.
 
Last edited:

Tradewinds

Well-known member
Joined
12 Jan 2003
Messages
4,042
Location
Suffolk
www.laurelberrystudio.com
edit: Crewman raises the question but one factor that has struck me is that people who re-galvanise suggest 'their' galvanising is better than the original. Whether this is an objective comment and accurate after time I do not know (people only comment when they look at their freshly coated chain not 4 years later). But it might be if you re-galvanise the sub-contractor takes greater pains to get it right, or the second time the coatings is better (because for some reason a second coat is actually 'better' on a previously coated substrate?).

close edit.
Certainly think that maybe the case with my original ACCO (1996) G40 chain which I had regalvanised when wintering in Aguadulce nr Almeria, Spain back in 1999. Still OK - although I don't anchor nearly as much nowadays :( .
 

MM5AHO

Well-known member
Joined
1 Oct 2007
Messages
2,517
Location
Central Scotland
Visit site
"There is a suggestion, an idea to which I do not subscribe, that the strict environmental restrictions that are put on galvanisers in 'Western' or developed countries has resulted in a reduction in the 'quality' or level of galvanising protection. Specifically it was suggested that Oz and New Zealand galvanisers were particularly poor (because, possibly, of these environmental restrictions)."

Dont agree with this, I can't see how the environmental controls demanded in Europe have any impact on galvanizing quality. The environmental controls relate to emissions of fume (from the flux), sound, and emissions to land - like acid spills etc. You can pollute a lot and do "good" galvanizing, or pollute hardly at all and do poor.


"I'm of the view, having looked at chain from America, Europe, Australia and China that their are variations in the quality of the product from individual galvanisers in one country much greater than the variation in quality between countries. However some suppliers do tend to supply product more prone to flaking than others, see below."

I suspect this is more to do with the variety of steel quality from one country to another than much to do with the galvanizing.

"I do suspect that sub-contract galvanisers do tend to treat chain the same way as a steel beam and simply coat with a minimum of coating - when in fact a thicker coating would last longer. This is possibly not the fault of the galvaniser but the chain maker (or whoever might be having the product coated - for example an anchor maker) who does not specifiy nor check that he gets what we, the end cusotmer, might want. Having said that, as evidenced by the interest in the thread, most do not know what they want!)"

The difference in treatment of customers with chain to others is more commercial than to do with quality. Galvanizers like truckloads of heavy structural steel - that goes well for high production rates. Chains and anchors are small quantities and just a pest, unless dealt with specifically. (We've got one such arrangement going on Bluemoment, where a number are lumping their chains and anchors together to avoid minimum order size charges etc )
Its not feasible to aim to coat "with a minimum of coating". What could the galvanizer do to get a "minimum" ? They don't really have that level of control, and even what control exists isn't commercially feasible to exercise. Galvanizers like to "bang it through" - get many tonnes per hour.
For the sailor, what counts and what the galvanizer can affect is the "welding together" in chain, where the chain comes back as a lumpy lump with links welded together by zinc. Galvanizers can exercise care to avoid that, but it takes time and time means money, and they're in the industry to make money. To recoup the cost of spending the time could often mean having to charge such a price that the buyer would decide to not re-galvanize.


"Vyv has a simple test to look at the adhesion of the galvanised coating which he developed from a British standard. He suggests cutting one side of a chain link and bending it through 180 degrees such that you form an 'S'. If the gal flakes off the coating is poor. The same effect can be seen when you test chain to failure - the gal on some chain can be seen to flake off on other chain the gal stretches with the underlying steel and remains adhered. You suggest gal flaking is not common, I'd beg to differ and say that using Vyv's test, or looking at broken chain, there are significant visual differences in coating adhesion (and I might highlight the Americans for having got it right). The tests might be a bit harsh for many gal steel applications, steel beams on a bridge are never going to suffer the stresses imposed in the test - but anchor chain is subject to harsh treatment. The gypsy and bow roller (if a metal roller) and certainly the seabed are hard masters and any gal subject to flaking might have shorter lifespan."

Galv flaking off doesn't necessarily mean "poor". To get it to flake it must be thick, so why not just measure thickness?
Adhesion is a misnomer in galvanizing. It's not adhered, its alloyed. It only alloys if its chemically clean, so its either there or not there. No "adhesion" actually means no coating. Flaking means that the deposited alloy is brittle and too thick, and that is controlled largely by steel chemistry.
 

Neeves

Well-known member
Joined
20 Nov 2011
Messages
12,578
Location
Sydney, Australia.
Visit site
Geoff,

You are going to a lot of time and trouble, thank you!

If running batches of chain is the way to re-galvanise why not set aside a quiet time, do you have a quiet month? and promote the idea that chain re-galvanising will be conducted every, say September (and only September). Or if you have a consortium of people wanting to re-coat - simply advertise that a good time is in the next month, or whatever. I know the Forum rules do not allow advertising - but I do not see how you can easily and quickly offer a service to members without getting it into a thread somehow (maybe a sympathetic member?) If it were cheaper to do in 'big' batches that might be an incentive to members to get their act in order.

One thing you are saying (I got the message :) ) is that steel quality is a significant determinant of galvanising quality. By this I am assuming you mean steel composition (not that the steel might be out of specification, it might be but its specific elements in the steel that are important), So if a steel quality does not galvanise well then as long as the chain maker uses the same steel then the galvanising will always be poor. The easiest way to improve galvanising would be to change the steel - which might not suit the supply 'chain' (sorry maybe better to use 'source of steel') or the quality (G number) of the chain. Catch 22.

But if, say, a G40 from a supplier has a poor galvanising life then it will remain poor until the steel source, chemical composition, is changed - which will probably change the chain characteristics, strength and elongation to break.

So what would be an ideal coating thickness, thick enough to give longevity not so thick that it flakes (who would think 'flaking' is a technical term and rejection of 'adhesion' as being invalid!)

Jonathan
 

MM5AHO

Well-known member
Joined
1 Oct 2007
Messages
2,517
Location
Central Scotland
Visit site
On steel quality:
I don't mean that the steel is out of specification that causes "bad" galvanizing, but rather specifically the Silicon (Si) and Phosphorous (P) levels. These are only two elements that steel makers vary to gain the physical properties of the steel they want. In most cases, the % of each element in steel for any specific grade is set as a range. e.g. "Si should be between 0.05% and 0.15%". So a steel can be in specification and different from another batch also in spec, but different chemistry.
It is possible to achieve most properties of the steel by varying the chemistry, but if it is known that the steel is to be galvanized (and an anchor chain manufacturer would know that), then they can also take that into account. All factors can be accommodated if they start out to design the whole system, rather than takes bits in isolation of the other processes.
Of course ungalvanized chain has no constraint on the chemistry specific to galvanizing, only a desire to meet the physical properties. But if some other party then uses that chain intending to galvanize and sell for anchor use, it might be inappropriate chemistry for galv, and end up looking poor from a consumer viewpoint.


To continue the puns..
If we can galvanize the supply chain to link together, such that all factors get anchored into the overall system design, then a good result might be achieved.
 
Top