Corrosion Trteatment On Aluminum Forks

[mixed]

A friend bought a pair of upside down KDX250 forks back from Japan from me. I'm told they have never been used, which could be true because the 'spring' feels very good.

There are tiny rust spots on the bottom of the chrome part, but it's not flaking. Any suggestions for this without rechroming?

The biggest problem is the corrosion on the top part of the aluminum, it's quite bad and flaking. What is the best way to treat this? There's info on the net but I don't have much time to do it myself.

Any suggestions for Thai shops that would do a half decent job. As you can see in the pic below, the forks look crap, but still work very well.

[mbox]

A friend bought a pair of upside down KDX250 forks back from Japan from me. I'm told they have never been used, which could be true because the 'spring' feels very good.

There are tiny rust spots on the bottom of the chrome part, but it's not flaking. Any suggestions for this without rechroming?

The biggest problem is the corrosion on the top part of the aluminum, it's quite bad and flaking. What is the best way to treat this? There's info on the net but I don't have much time to do it myself.

Any suggestions for Thai shops that would do a half decent job. As you can see in the pic below, the forks look crap, but still work very well.

I had some aluminium corrosion on my honda bros 650 too. I was sourcing for the same info, here is what i was suggested. Use sandpaper starting from rough - and moving up to slighly less rough sandpapers, ending these pieces to very fine sandpaper and it will shine again. To protect a clear lacquer should be applied.

I have not tried this but it sounded ok, why i never tried ? i had sold the bike by then...

mbox

[mixed]

Yes, this sounds similar to what I read, except in my case I'd probably start with a wire brush. Problem is I'm short of time, I'd like to get a Thai to do it, but am worried they'll stuff the whole thing up, especially as the forks look so bad they probably consider them worthless.

[thaicbr]

I'd like to get a Thai to do it, but am worried they'll stuff the whole thing up,

Off course they will stuff them up. Unless you sit and watch them while they are doing it. Do it yourself much easier and less headache. I wish i would listen to my own advice sometimes..........but that's a different story!

To be fair it depends on where you are Ray has had good luck with his guy in Udon and there are a few good places in CM and KK

Edited October 28, 2009 by thaicbr

[BSJ]

Wasting your time. Once alloy gets that bad the integrity of the part is compromised. Cast aluminium forms a hard skin where it contacts the mould in the casting process. It's only a few microns thick. But it's not enough to give a good permanent finish. If the part isn't sprayed with a protective coating oxidization occurs when the part comes in contact with air.....while it's still in the factory! For example, look at all those alloy wheels out there, which are all coated before they leave the factory. Imagine what they would look like if they weren't coated! The air, brake dust, exhaust fumes, dirty water would kill alloy wheels in a few years if left natural.

[dumball]

I have never seen a pair of competition forks in that condition and we have rebuilt hundreds of them , where were they stored , in the Adaman ?

[LivinLOS]

I have also never seen forks that bad, I mean stored under salt spray or something..

However I would have assumed you could polish off the corrosion as I would have thought it was surface only, not deep into the metal. Thats something that I dont think the photo will show.

Last thing you want to give way on you is a set of forks !!

[Powerband]

Will reannodizing them work?

[mixed]

I have never seen a pair of competition forks in that condition and we have rebuilt hundreds of them , where were they stored , in the Adaman ?

The came from Japan, from what I've read they probably were stored with something that caused a chemical reaction. I don't believe they ever been used, I'll have a go at cleaning them and see just how bad it is.

[dumball]

I would be terribly concerned with the state of the internal working components , should there be parts inside whos integrity have been compromised , you could be attaching a dangerous component to the front of your machine . You will need some special tools to complete this operation , proceed with caution , parts can be expensive , what you may have gained on the swings , you could very well end up losing on the roundabouts , good luck in your endeavours .

[mixed]

I would be terribly concerned with the state of the internal working components , should there be parts inside whos integrity have been compromised , you could be attaching a dangerous component to the front of your machine . You will need some special tools to complete this operation , proceed with caution , parts can be expensive , what you may have gained on the swings , you could very well end up losing on the roundabouts , good luck in your endeavours .

My main concern is that the corrosion would have weakened the forks from the outside, as the inside has oil. The shocks seem fine, like new. I will have someone check it out when I finally get to use them.

From what I've read, the corrosion probably looks a lot worse than it is, because it is lifting away rather than eating in.

I took them to a local mechanic, who didn't think it was a problem, of course he may not be an expert, however what he suggested was exactly what I'd read on the net. He's sanding them down gradually working to the finest paper.

[dumball]

How many pairs of upside down forks do you think your 'Local mechanic'? has even seen let alone had real experience with ? . Corrosion eats into material , that is what makes it flake away , are you sure there is still oil in those forks or are you just presuming ?

[mixed]

How many pairs of upside down forks do you think your 'Local mechanic'? has even seen let alone had real experience with ? . Corrosion eats into material , that is what makes it flake away , are you sure there is still oil in those forks or are you just presuming ?

Sure he's no expert on upside down forks, but he has seen a few and rebuilt bikes from absolute rubbish to looking brand new.

There is another guy who is an expert, I'll see what he has to say. The only way to be sure there's oil is to open them up, which I'll let some else do. The seals look fine, there's no sign that anybody has opened them.

I'll have it checked out properly before using them, but looking at them today, I think they'll be OK, but probably look a bit rough.

[BSJ]

Chemical fatigue can lead to hairline cracks that maybe difficult to see before a collision....but they will be more noticeable after the collision!

Ps: I hope your sand paper guy follows the correct testing procedure as found in the following.

</h3>

<h3>Journal Title

Measurement science & technology ISSN 0957-0233

Document title

Crack detection in Al alloy using phase-contrast neutron radiography and tomography

Author(s)

FIORI F. ; HILGER A. ; KARDJILOV N. ; ALBERTINI G. ;

Abstract

A phase-contrast neutron tomography experiment has been carried out in order to verify the capability of this imaging technique to visualize cracks in a poor neutron absorber like an Al alloy. 2024 Al alloy fatigued specimens were used to this end. The results showed the effectiveness of the experimental method, putting into evidence how it can actually detect the cracks, while standard neutron radiography cannot. Some features of the cracks can be estimated as well, such as their length and through-thickness depth. The method could be helpful in detecting cracks and determining their morphology in Al alloys, eventually replacing synchrotron radiation μ-CT, especially in the case of massive samples (several cm), where x-rays are completely absorbed.

Further reading: http://www.iop.org/EJ/abstract/0957-0233/17/9/015

Edited October 30, 2009 by BSJ

[mixed]

Chemical fatigue can lead to hairline cracks that maybe difficult to see before a collision....but they will be more noticeable after the collision!

Ps: I hope your sand paper guy follows the correct testing procedure as found in the following.

I think we're getting a bit carried away here, it's not rocket science after all.

The forks have been cleaned and polished, they came up very nice.

They look like chrome, but left untreated will eventually corrode again.

Any suggestions?

[LivinLOS]

[mixed]

This site has certainly earned it's reputation for being negative and unhelpful. The part of the forks that was corroded is not the part that's collapsing in the irrelevant pic.

I'll Join a Kawa site and see what they have to say, the same corrosion problem I've seen on many KDX forks, so hopefully ppl there will know something, rather than googling for irrelevant pics and info on 'phase-contrast neutron tomography experiments'