Does anybody know anything about metal and corrosion?

altruistica

altruistica

Member
I have a weird problem with a Fostex D2424LV MKII that I recently bought from Ebay.

When I bought it I noticed slight corrosion on the back panel, so I took the cover off to find corrosion to the metalwork in several places. As the circuit boards were free of corrosion and after the unit passed a thorough test of all functions, I decided to keep the unit. The MKII offers the ability to transfer WAV files and whole projects via Compact Flash cards and has no SCSI backup facilities (it hasn't got a SCSI port). I also have a MKI unit which means I can swap caddies between the two and easily move projects that were recorded live at gigs into the studio for mixing / re-recording / overdubs etc.... and backup these projects either as WAVS or project backups via CF card to a network drive...... well that's the idea anyway and it should work out.

As you can see from the pics here though,

https://www.flickr.com/photos/33383402@N06/albums/72157660611277831/show

the difference in the corrosion of the casings are notable. I've just bought some generic caddies to replace the Fostex ones which either cost an arm and a leg if you can find them. On removing the cover of the MKII unit I noticed what looked like some kind of liquid (it may have been water in the form of condensation) on the top of the inside of the cover. This is strange as neither the room is overly damp or cold. I have never seen this before with any piece of equipment and wondered whether some strange metal corrosion process is going on whereby a possible galvanised steel covering breaks down to produce water as a by-product?

Anybody got any explanation for this?

Thanks
Al
 
Probably simply condensation. I'd tape bags of silica gel inside, and forget it, if the unit works ok. In many cases, it's just a bad batch of metal, and condensation starts the oxidisation process, or sometimes its already oxidisation under the surface finish. I've got a couple of identical bits of kit and inside one is rusting away really badly, while it's partner, always in the same location for it's entire life is clean and still shiny inside.
 
I'm not sure but I'd likely suspect something like sea-side exposure, as in this unit having resided somewhere close to the coast by an open window or stored in a garden shed which was far from air tight and the moisture in the air just did its thing over a period of time.



Cheers! :)
 
Thanks for the replies guys.
Rob, is the unit you mention in danger of transferring damp to the circuit boards? I'm thinking of stripping the MKII unit down and painting the inside with Hammerite silver paint (I've got some left over from another job). The D2424LV is quite a basic machine (four or five boards). I think the most difficult thing to get off would be the input /output jacks which look like they're secured by metal retaining strips If these need removing from the board then forget it....but if they simply lift off then it might be worth it.
I don't want this unit to fail simply because I don't do anything.

Al
 
you have surface corrosion and inter granular corrosion. The correct procedure would be to remove all of the corrosion and then treat the affected areas with a rust inhibitor such as LPS 3. I know taking all of the components out may not be an option. treating the areas without cleaning it will not stop it but it will slow it down alot. LPS Procyon is a corrosion inhibitor. the corrosion will not stop unless it is removed, but you can slow it down a good bit.

http://www.lpslabs.com/product-details/612

:D
 
The Ghost of FM said:
I'm not sure but I'd likely suspect something like sea-side exposure...
Click to expand...

Yeah...that was the first question I was going to ask...what part of the country did it come from.


Atkron205 said:
you have surface corrosion and inter granular corrosion. The correct procedure would be to remove all of the corrosion and then treat the affected areas with a rust inhibitor such as LPS 3.
Click to expand...

Yup...that's what I would do...clean off the corrosion, and then apply a sealer/inhibitor to keep it from spreading any more.


If it's just the casing and non-operational parts...I wouldn't worry about it if everything works OK.
The casing metal might have been poorly treated during manufacturing and that's why it succumbed to the corrosion.
 
miroslav said:
Yeah...that was the first question I was going to ask...what part of the country did it come from.




Yup...that's what I would do...clean off the corrosion, and then apply a sealer/inhibitor to keep it from spreading any more.


If it's just the casing and non-operational parts...I wouldn't worry about it if everything works OK.
The casing metal might have been poorly treated during manufacturing and that's why it succumbed to the corrosion.
Click to expand...

LPS also makes a electronic cleaner protector that is safe for components. I suggest LPS because it is a very good product. kinda expensive but a can will last a long time. used it all the time when I worked in Aviation. it is the only stuff I use.

http://www.lpslabs.com/product-details/578
 
Thanks for those replies.

I bought the unit from someone in central London. Whether it had lives somewhere else prior to this I don't know.

I am concerned that the casing was wet to the touch when removed....this seems to suggest it's drawing a lot of moisture out from the air, so anything that slows down this process has to be good. I think I'll contact Fostex and see if they've seen this before.

Thanks Al
 
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