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Almondo5

Joined:

Jun 09

Posts: 5

Almondo5 says:

Powdercoating - DON'T!!!

Just read the item on powdercoating R1 wheels in this weeks MCN. DON'T DO IT!!  I got my wheels done a couple of years ago and thought they looked great! 6 weeks ago I got a new tyre fitted to the back wheel. I took the wheel home to fit it to the bike and decided to give it quick clean before fitting it. I found major cracks around the base of 2 spokes (at the hub) and more cracks around the rim on the 3rd spoke!!!

I don't recall hitting any mega potholes lately so can't explain what has caused the damage. I've spoken to a few mates and the guys at the tyre fitters and they all say the same thing - POWDERCOATING!

  I'm off to buy a lotto ticket - THIS WHEEL WAS READY TO COLLAPSE AT ANY TIME!

Check the pics.

Attached images:

  1. CRACK1  
  2. CRACK2  
  3.  
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  • Posted 6 years ago (27 June 2009 00:54)

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jaffa90

Joined:

Mar 09

Posts: 8892

jaffa90 says:

powdercoating

Shocking:shock: but thanks for the report,it must be a chemical reaction ,but a couple of years to come about.:upset:

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parapanfan

Joined:

Apr 06

Posts: 2672

parapanfan says:

Is that in the coating or the wheel itself?

Seems severe to crack a wheel that badly without any obvious cause.

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smoto5

Joined:

Mar 09

Posts: 4548

smoto5 says:

Have seen

corrosion underneath powder coating, from moisture seeping under from damaged areas of coating, then the coating cracks and flakes off, so possibly salt induced corrosion in an existing fault. But actual cracks in the alloy point more to damage from impact, either before or after coating, was this a repaired wheel, ie. rim damaged and repaired? Coating temperatures are not usually excessively high, however there is a possibilty in some types of castings of heat releasing stresses in the material from the casting process

Wheels have been steadily getting lighter as manufacturing techniques have improved and demand for lighter sportier bikes carries on, wheels making a very notable difference to handling as they are lightened, and our roads have been getting more and more unfit for purpose, potholes bumps and so on.

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oscarthegrouch

Joined:

Oct 05

Posts: 3142

i wonder

wow you are lucky mate. i will be watching this post with great interest as i have had the wheels powdercoated on my fzr 600r . i wonder if is just certain wheels that are prone to cracking .

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crackfinder

Joined:

Mar 09

Posts: 351

crackfinder says:

cracks

As smoto5 says, it could be cracks in the coating,

but looking at photo 1, it looks to me like the metal is cracked, if you look closely at the greyish "crack" at the base of the spoke you can see a fine dark line in the centre of the greyish area, this looks like a crack to me, the greyish bit is the metal under the coating and the coating is chipped off along either side of the crack, as the wheel flexes through torque and load stress's the metal either side of the crack will move, and as the two edges of the crack move independently of one another the coating along those edges gets chipped off exposing the crack in the centre.

Having said all that if you can't tell if it's cracked or not visualy, then you need to get it tested, there are various techniques that would determin if the metal is cracked or not.

Not sure how much heat is applied to the wheel during the coating procedure, but If there were minute cracks in the original wheel, application of enough heat would definitely "open them up" make them larger and more noticeable.

it's worth noting too that by heating any metal above certain temperatures will change the properties of the material, which can lead to localised hardening and embrittlement, causing cracks, or even softening and weakening. the same applies to cooling after heating too.

[This Reply has been modified by the Author]

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Almondo5

Joined:

Jun 09

Posts: 5

Almondo5 says:

More info

Thanks for your posts guys. Here’s some additional background info:-

 

  1. The worst of the cracks penetrate well into the alloy, if not right through the wheel.
  2. I don’t do stunt riding.
  3. The bike hasn’t been run through winter conditions so no exposure to salt.
  4. The wheel has never been repaired – I’ve had the bike from new.
  5. I don’t recall hitting anything (pothole, etc) hard enough to cause this kind of damage.

 

I’m still looking for an answer. General consensus with people I’ve spoken to still point the finger at powdercoating!

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46vale46

Joined:

Jun 09

Posts: 22

46vale46 says:

BritChopper

is a forum with a whole host of clever people that have had all sorts of things powdercoated, and the concensus is that the wheel may have been faulty before the powdercoat was applied, and that the heating has just shown up the damage.

A word with aerocoat might help clear up any confusion on the process???

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James600zx

Joined:

Sep 07

Posts: 2801

James600zx says:

Powder coating and alloy weakness.

If heat is involved the rates of heating and cooling will affect the temper of the alloy. If properly controlled the casting ought to maintain its strength, but if the coater's only concern is applying the finish you can end up with a casting which is either soft or brittle.

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podmet

Joined:

Nov 10

Posts: 1

podmet says:

Cracks in powdercoated wheel.

I just saw this, I dunno if I'm too late to post this but here goes for my first forum post. Theyre some scary cracks. I would be surprised if it was due to a 'chemical reaction' between the aluminium and the coating. If the P/C process was suitable for aluminium, I would be surprised if the heat from the process had much to do with it either, but it depends what type of plastic they were coating it with which would dictate what temp they were taking it to. I'm no P/C expect but if the coating was PVC the temp probably wouldnt be much more than 100C. The wheels are most likely cast aluminium which should be fine at this temp.  Heat treatment is complex; (much) higher temps could anneal and soften aluminium but on the other hand it could ‘artificially age’ or precipitation harden it and make it stronger, it all depends on what type of aluminium alloy it is and there are hundreds.  To a cast alloy it probably wouldnt make a great deal of difference, theyre generally not very strong anyway.  'Crackfinder' is right, there are embrittling mechanisms too which are very alloy-specific, but generally aluminium is not too sensitive to cooling rates. But I’m not thinking that this is a strength issue; it doesn’t look like an overload failure. It doesn’t look like corrosion has travelled under the coating much either.  By the position and appearance, it almost looks like a fatigue crack to me. If this coating is not very flexible, it may have cracked as the wheel flexed, and if the coating was adhered strongly to the metal, the crack might have carried on into the metal. It could have happened due to tensile stresses in the coating.  It is common practice to ‘peen’ the surface of a critical component to impart compressive stress to improve fatigue strength, so you can imagine that any tensile stress would make matters worse.  I suppose it could be stress-corrosion cracking, which would require a crack in the paint too.  Either one is a gradual process. Dont get me wrong, I’m not saying that is the cause, I’m just saying it could be.  Send me the wheel and I’ll have a look at it for you!!  Pity the original post was 2 years ago!!  Dammit, I want to know now!

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smoto5

Joined:

Mar 09

Posts: 4548

smoto5 says:

Not too late at all, any input is good!

firstly welcome to the forum :-)

Good to see your views on it, a more expert opinion is of use as this may affect other people too, shame the original poster has given no further input, but of course he may have wanted to move on, it's an alarming thing to find!

My thoughts were along the lines of hydrogen embrittlement, but of course that's just a stab in the dark, and would have expected that to manifest differently, ie more cracks in a different direction. Seems possible there was an underlying fault from the casting process or an impact damage ie. pot hole, something run over?

I would think the only definite way to get more info would be to inspect and test in a metallurgy lab with the various processes, cross sections, hardness tests, impact tests and so on (forgotten names of most of those tests now!)

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