how to tell a galvanised spoke from stainless

[alexnharvey]

I believe there is no evidence you would accept because it would mean also accepting you were wrong.

I've demonstrated that they are plated to satisfy my own curiosity and I think sufficiently to demonstrate it for any reasonable and curious person.

I think you're not a reasonable person. Others can draw their own conclusion about that and about the spokes from the posts and pictures in the thread.

More pics in a few days.

The offer of some spokes remains open to you if you'd like to demonstrate that they are stainless.

[thatsnotmyname]

I believe there is no evidence you would accept because it would mean also accepting you were wrong.

I've demonstrated that they are plated to satisfy my own curiosity and I think sufficiently to demonstrate it for any reasonable and curious person.

Like I said earlier, science doesn't care what you believe - or in this case, what you 'think'. Whether you 'think' it is stainless or not is irrelevant. Nothing you have presented here so far proves they are not stainless.

I think you're not a reasonable person.

Ironically, I appear to be considerably more reasonable than you, on the basis that I am challenging your presumptions, which you seem to be making with little or no evidence. Like I said earlier, nothing you have said or shown on here proves anything. I'm trying to be guided by the science and the science suggests that it can currently all be explained within the characteristics of stainless. It doesn't necessarily prove they are stainless, but it certainly doesn't prove they are galvanised either. I'll leave you to reconcile that logic for a while....

[alexnharvey]

I'm done, others can draw their own conclusions on both questions.

There's sufficient evidence to answer both but no doubt you'll continue to add more posts that serve to demonstrate my second point all the better. Good luck to you

[alexnharvey]

Some sort of orangey stuff on spoke 3 and falling to the bottom of the glass around it.

Little change on the others.

[Oldjohnw]

Don't you love it when an apparently simple question like that of the OP takes 10 pages and lots of often bitter argument.

Vive la difference!

[Brucey]

Don't you love it when an apparently simple question like that of the OP takes 10 pages and lots of often bitter argument.

"not at all"

[alexnharvey]

Heavier rust on the lower part of number 3, the filed spoke, with the remaining plating still protecting the upper submerged area.

[Brucey]

I'm surprised it is rusting that well; I suspect that if there was no plating submerged at all (on the spoke in question), the corrosion rate would be much higher.

cheers

[alexnharvey]

It rusts orange then the rusts falls off leaving it black. Could that be part of the zinc's protective action?

Same order a before 1 DT Swiss Stainless (control), 2 lightly sanded, 3 heavily filed, 4 no abrasion. Note the camera has changed.

Orange Iron oxide and maybe zinc chloride in the bottom of the glass?

[Brucey]

Iron has several oxidation states and it isn't unusual for a corroded layer to contain more than one of them. Between the oxidation state and the physical nature of the oxide, you can get a wide variety of different colours appearing. So it might be that....?

cheers

[Johnfranklyn]

Long ago butchers shop fitting needed to be 18 8 stainless steel to prevent rusting. Stainless steel cutlery knives have to have a bit of carbon steel if you want a good edge. ie Stainless steel spokes should not stick to a magnet if you use the word “Stainless”
If spokes attract magnet it may just be for a bit more tensile strength. They can still be rust resistant.

[pedals2slowly]

Don't you love it when an apparently simple question like that of the OP takes 10 pages and lots of often bitter argument.

Vive la difference!

Wow, fascinating stuff to occupy us in the lock-down isn't it!

Just been out to the garage and using a good rare-earth magnet tested about 30 different spokes.
As suspected the plated and galvanised spokes are noticeably more attracted to the magnet. I would be happy to use my feel to distinguish between the plated/galv and stainless. The 'stainless' spokes vary in attraction, some barely noticeable. I seem to remember the early stainless spokes were pretty brittle - maybe a different composition?

I used to use the magnet test on deliveries of super duplex stainless valves for north sea oil rig pumps, anything that had a strong attraction became suspect and invited even more thorough checking of material mill certificates etc than normal.
A batch that arrived from China already starting to 'rust' didn't need the magnet test and turned out that the manufacturer was just churning out 'stainless steel' valves copying the same mill certificate over and over again!

Moral is stainless spokes ain't necessarily going to be stainless. (I doubt there is any material traceability)

The limited garage test also confirmed that I am able to visually tell the difference between plated, galvanised and stainless spokes, though I do remember making a mistake once in the last 40 years.

Loads of good info on stainless steel here by the way. https://www.bssa.org.uk/

[pedals2slowly]

Stainless steel spokes should not stick to a magnet if you use the word “Stainless”

There's no legal definition of stainless, but generally 10.5 % Cr or more
Typically magnetic stainless steels are ferritic grades 409, 430 and 439 martensitic grades 410, 420, 440 and Duplex
Does anyone know what grades are used in spokes?

https://www.bssa.org.uk/faq.php?id=24

[Brucey]

very many stainless steel spokes are made in 300 series stainless steels, or modified variants thereof. These compositions are nominally austenitic but in reality normally contain a small amount of ferrite. The exact amount of ferrite (as indicated by a meter which measures the magnetic properties) depends on both the exact composition and the thermomechanical history.

There are three main effects in wrought products;

- composition
- cold work
- heat treatment

The Schaeffler diagram predicts the ferrite content based on composition and is accurate for products that have been solution annealed. However most products are not solution annealed. As-cast most grades contain more ferrite than the diagram would indicate.

Cold work typically transforms some austenite (non-magnetic) to martensite (magnetic). This is relevant in spokes, because the wire is cold-worked (at the steel producers or a specialist wire-makers) before it is made into spokes, and of course butted spokes are heavily worked when they are made too; the skinny bit is variously drawn, swaged and/or forged to make it the correct shape, and the head, J bend and spokes are of course worked too.

The cold work confers a good measure of the strength in the finished spoke. Thus if finished spokes were solution annealed they would default to the ferrite content as indicated on the Schaeffler diagram, but they would also most likely be too soft.

Not relevant to spoke manufacture is welding of stainless steels. A variant of the Schaeffler diagram known as a 'De Long' diagram is used to help predict ferrite content; weldments tend to have a different composition (because of filler material added, loss of volatile alloying elements etc) and can be critically sensitive to ferrite content; if it is too low welds tend to crack. Even 'within grade' some batches may crack where others don't.

Between all these effects the net outcome seems to be that spokes made in nominally austenitic stainless steels can have appreciable amounts of ferrite in them and/or are magnetic. Sometimes you can detect a difference between the centre section of butted spokes and the heavier gauge ends. However because this is so sensitive to composition not all spokes , even those which are meant to be the same, from the same manufacturer, will be similarly magnetic.

A further complication, when offering a magnet up to spokes, is the magnetic susceptibility of the material. This is non-linear, so that the apparent amount of ferrite (as indicated by the pull of the magnet) is sensitive to the applied field strength. This normally manifests itself by some spokes appearing to be almost entirely non-magnetic when a weak magnet is offered up to them, but when a much stronger magnet is used, you can get the magnet sticking pretty hard, i.e. a greater proportion of the maximum attraction such a magnet would manage when offered up to a fully ferritic specimen.

A long time ago some spokes were advertised as being made from 'a ferritic stainless steel' but I have not seen any described thusly for a long time. Where material is indicated it is often described as an 18-8 stainless steel; when assessed with a magnet there is usually more magnetic attraction than you might expect based on composition alone.

cheers

[cromo]

I know a lot has been written about this topic but here is a another possible way of telling if a spoke is galvanised or not. You do however need a multimeter set to read millivolts. The advantage is that the results are instant, you do not need to wait to see if rusting occurs.

Basically you set up two electrodes into some salty water and measure the voltage between them. If you use two stainless steel spokes as electrodes then the voltage will be very small or nil. If you use a galvanised spoke and a stainless steel spoke as electrodes then the voltage should be significantly different to that measured above.

Alternatively, a galvanised spoke, used in the above set up, would be expected to give different readings when used intact and then used with the zinc coating removed by abrasion. A stainless steel spoke will presumably show little difference if used intact and then abraded.

N.B. I do not have a millivoltmeter, so I cannot test the above. It is all hypothetical. I think it should work! Probably best to degrease the spokes before taking any measurements.