how to tell a galvanised spoke from stainless

General cycling advice ( NOT technical ! )
Brucey
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Re: how to tell a galvanised spoke from stainless

Postby Brucey » 11 Apr 2020, 12:45pm

you clearly don't understand how galvanising works (tip; try looking up 'sacrificial anode'), or just how difficult it is to remove all of it from a surface either, come to that. Thus your 'conclusions' are in error.
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thatsnotmyname
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Re: how to tell a galvanised spoke from stainless

Postby thatsnotmyname » 11 Apr 2020, 12:56pm

Brucey wrote:you clearly don't understand how galvanising works (tip; try looking up 'sacrificial anode'), or just how difficult it is to remove all of it from a surface either, come to that. Thus your 'conclusions' are in error.


I do though, Brucey. Galvanising is a surface treatment, so can be removed relatively easily with the right amount of application - which doesn't generally include 'light abrasion' - but it can be removed, nevertheless. Maybe the OP could clarify how he did it.

Meanwhile, personally, I think your conclusions are in error - and I think you are clinging onto the 'plated' argument simply because I originally stated otherwise. If I had said at the start that the spoke was galvanised, you would probably have said it was stainless. Not that you'll ever admit it.

alexnharvey
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Re: how to tell a galvanised spoke from stainless

Postby alexnharvey » 11 Apr 2020, 1:05pm

Time will tell.

The first abraded spoke had a light to medium rub with a aluminium oxide 80 grit.

The second was filed with a small triangular file, then a light rub with a bit of 80 grit again to polish it.

Brucey
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Re: how to tell a galvanised spoke from stainless

Postby Brucey » 11 Apr 2020, 1:19pm

….I do though, Brucey….


I think not; it looks like I shall have to spell it out for you;

1) if you want to remove all zinc plating from a surface (eg for welding) it has to be chemically stripped or the surface ground back. Using abrasive paper most folk would get very bored before they successfully removed it all.

2) if there is any zinc left on the surface nearby ( and by 'nearby' that would mean within an inch or two and also exposed to the solution in this context) then this will corrode preferentially to the steel. That is how zinc coatings work; sacrificial anode.

So if you want something that was zinc coated to 'rust' (i.e. show the classic red-brown colour) then you need to remove ALL the zinc from the immersed part and then show it the corrosive condition. Unless you do this any remaining zinc will corrode preferentially, and until that is exhausted, the steel won't show 'rust'.

I repeat (for the 'n'th time) those are plated spokes. I literally couldn't give a rat's backside who says otherwise; they are mistaken, simple as that.
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thatsnotmyname
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Re: how to tell a galvanised spoke from stainless

Postby thatsnotmyname » 11 Apr 2020, 1:26pm

Brucey wrote:
….I do though, Brucey….


I think not; it looks like I shall have to spell it out for you;

1) if you want to remove all zinc plating from a surface (eg for welding) it has to be chemically stripped or the surface ground back. Using abrasive paper most folk would get very bored before they successfully removed it all.

2) if there is any zinc left on the surface nearby ( and by 'nearby' that would mean within an inch or two and also exposed to the solution in this context) then this will corrode preferentially to the steel. That is how zinc coatings work; sacrificial anode.

So if you want something that was zinc coated to 'rust' (i.e. show the classic red-brown colour) then you need to remove ALL the zinc from the immersed part and then show it the corrosive condition. Unless you do this any remaining zinc will corrode preferentially, and until that is exhausted, the steel won't show 'rust'.

I repeat (for the 'n'th time) those are plated spokes. I literally couldn't give a rat's backside who says otherwise; they are mistaken, simple as that.


Not sure how any of that is relevant. There is no need to remove 'all' the plating across the entire surface area. All he has to do is take any part of it back to bare metal (which can be done with a file, as the OP stated he has used) and the affected area will behave differently to the intact areas around it. So in other words, if that 'non-stainless' spoke was going to start showing signs of rust, it would have done so by now. The internet is full of pictures of rust-damaged, galvanised steel.

Nice to see your "I'm right and everybody else is wrong" attitude in full swing. Presumably when you are proved wrong, will you come back and show some humility? Ironically, you called me 'pig headed' in a post elsewhere :lol:
Last edited by thatsnotmyname on 11 Apr 2020, 1:37pm, edited 1 time in total.

alexnharvey
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Re: how to tell a galvanised spoke from stainless

Postby alexnharvey » 11 Apr 2020, 1:30pm

You are wrong about that because you do not understand how a sacrificial anode protects the part, despite it having been explained to you quite clearly.
It is not just a coating like Chrome plate or paint

See here also https://en.m.wikipedia.org/wiki/Galvanic_anode

I have tried to remove it all with the file but some will remain in the threads for example and bits I have missed with the file.

thatsnotmyname
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Re: how to tell a galvanised spoke from stainless

Postby thatsnotmyname » 11 Apr 2020, 1:41pm

alexnharvey wrote:You are wrong about that because you do not understand how a sacrificial anode protects the part, despite it having been explained to you quite clearly.
It is not just a coating like Chrome plate or paint

See here also https://en.m.wikipedia.org/wiki/Galvanic_anode

I have tried to remove it all with the file but some will remain in the threads for example and bits I have missed with the file.


I know it's not a coating - there's no need to clarify that. As I said just now, 'sacrificial anode' or not, the web is full of pictures of galvanised steel where rust has taken hold in patches where the surface has been compromised. Some of that is probably down to the quality of galvanising in each individual case, while others are probably more indicative of "the theory not reflecting the reality." Galvanising is no guarantee of a defence against that and the cathodic protection offered to gaps, damage or deliberate removal of the galvanising is limited to a relatively small, local area - an important consideration that Brucey somehow omitted from his 'clear' explanation.

Brucey
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Re: how to tell a galvanised spoke from stainless

Postby Brucey » 11 Apr 2020, 7:08pm

Zinc is a coating, it just doesn't have to work as a barrier coating in order to be effective. Believe it or not the protection afforded by a sacrificial anode varies depending on the way in which ion transport can occur within the electrolyte. In a salt solution the sacrificial anode will work over a reasonable range. In an environment with no continuous electrolyte and/or a more aggressive corrosion condition, the same range of protection is not afforded. Hence I was careful to indicate the likely range of the sacrificial anode in this case.

If you remove all the zinc coating by grinding (rather than remove it locally or just scuff it up a bit using an abrasive) from a plated spoke and put it into salt solution it will go rusty pdq. If you don't believe me, try it, it is simple enough to do.

FWIW the plated spokes are corroding in the salt solution; Zinc oxide so formed is usually black in colour, and that is what we are seeing.
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thatsnotmyname
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Re: how to tell a galvanised spoke from stainless

Postby thatsnotmyname » 11 Apr 2020, 7:32pm

Brucey wrote:Zinc is a coating, it just doesn't have to work as a barrier coating in order to be effective. Believe it or not the protection afforded by a sacrificial anode varies depending on the way in which ion transport can occur within the electrolyte. In a salt solution the sacrificial anode will work over a reasonable range. In an environment with no continuous electrolyte and/or a more aggressive corrosion condition, the same range of protection is not afforded. Hence I was careful to indicate the likely range of the sacrificial anode in this case.

If you remove all the zinc coating by grinding (rather than remove it locally or just scuff it up a bit using an abrasive) from a plated spoke and put it into salt solution it will go rusty pdq. If you don't believe me, try it, it is simple enough to do.

FWIW the plated spokes are corroding in the salt solution; Zinc oxide so formed is usually black in colour, and that is what we are seeing.


You're just repeating yourself now Brucey. In any case, I don't see any corrosion in those pics. Like I said earlier, discoloration is not corrosion. You would expect bare metal to show significant signs of rusting by now and it simply hasn't happened.

Meanwhile, I'll offer this quote from a write up on a study which looked at this very issue. I'll provide the link too, if you prefer. Just let me know.

The cathodic protection of zinc is limited by the width of the damaged area. The study conducted by Zhang and Xing showed that a critical distance exists signifying the maximum distance away from the zinc that it will protect the exposed steel (Figure 2, above). The maximum protection distance found (assuming a thin layer electrolyte and moderate zinc surface activity) was slightly greater than 1/4" (7 mm). However, once the width of the exposed steel increased beyond this distance, the protection distance decreases to a minimum of just over 1/8" (4 mm).


In other words, protection is not universally guaranteed regardless of damage. And once the exposed area goes beyond 7mm, you will start to see rust. Hope that clears things up.

Brucey
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Re: how to tell a galvanised spoke from stainless

Postby Brucey » 12 Apr 2020, 2:05am

You clearly have not read or understood what I have written, or something.

That discolouration is corrosion of the zinc plating.

I am (once again) bored stiff of this; another loopy rabbit hole beckons and I'm not going to be dragged into it.
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alexnharvey
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Re: how to tell a galvanised spoke from stainless

Postby alexnharvey » 12 Apr 2020, 9:10am

IMG_20200412_085609.jpg


1. DT Swiss stainless (alpine iii) after 1 week or so

2. Plated spoke, lightly abraded, after 1 week or so

3. Plated spoke, filed and abraded, overnight.

4. Plated spoke, no abrasion or cleaning, overnight.

IMG_20200412_085645.jpg


Spokes 2-4 close up.

IMG_20200412_085809.jpg


Rust left in the bottom of the glass below spoke 3.
Image Attachments
IMG_20200412_085727.jpg

thatsnotmyname
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Re: how to tell a galvanised spoke from stainless

Postby thatsnotmyname » 12 Apr 2020, 9:21am

Brucey wrote:You clearly have not read or understood what I have written, or something.

That discolouration is corrosion of the zinc plating.

I am (once again) bored stiff of this; another loopy rabbit hole beckons and I'm not going to be dragged into it.


You always say that as well..

thatsnotmyname
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Re: how to tell a galvanised spoke from stainless

Postby thatsnotmyname » 12 Apr 2020, 9:27am

As expected, the pics prove nothing unfortunately..

https://laforceinc.wordpress.com/2015/0 ... l-rusting/

What causes discoloration and oxidation of stainless steel?
All grades of stainless steels are iron-based alloys with significant percentages of chromium. Typically, stainless steels contain less than 30% chromium and more than 50% iron. Their stainless characteristics stem from the formation of an invisible, adherent, protective and self-healing chromium-rich oxide (Cr2O3) surface film. While stainless steels are resistant to rusting at room temperatures, they're prone to discoloration by oxidation at elevated temperatures due to the presence of chromium and other alloying elements such as titanium and molybdenum.

Factors that contribute to increased oxidation include high dew points, high oxygen and oxides of lead, boron and nitrides on the surface.

alexnharvey
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Re: how to tell a galvanised spoke from stainless

Postby alexnharvey » 12 Apr 2020, 11:35am

thatsnotmyname wrote:As expected, the pics prove nothing unfortunately..


It seems quite fortunate for you to believe that, funnily enough. :lol:

thatsnotmyname
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Re: how to tell a galvanised spoke from stainless

Postby thatsnotmyname » 12 Apr 2020, 11:54am

alexnharvey wrote:
thatsnotmyname wrote:As expected, the pics prove nothing unfortunately..


It seems quite fortunate for you to believe that, funnily enough. :lol:


Nothing you have said or shown on here proves that the spokes are not stainless. I'm simply responding with perfectly valid explanations of why they could be behaving in the way they are. So far, everything you have presented here is explainable and nothing you've said or done so far proves they are not stainless. You and Brucey won't want to hear that, but it remains true whether you like it or not.

As the old saying goes, "science doesn't care what you believe"