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Corrosion SEAS Magnesium Drivers
Corrosion SEAS Magnesium Drivers
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Old 17th December 2016, 04:24 AM   #21
eriksquires is offline eriksquires  United States
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One other idea is a bag of rice! Rice is terribly absorbent (hydrophillic) and will help dry out the inside of the speaker in a couple of days.

Put it in a very porous cloth bag, or in a dish at the bottom.

Best,

Erik
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Old 17th December 2016, 06:03 AM   #22
ICG is offline ICG  Germany
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Originally Posted by Mardi View Post
About five years ago I bought some SEAS Excel drivers (W12CY001). I put them in a pair of loudspeakers I built for a friend. Recently he informed me that the drivers had developed corrosion on the magnesium cones. I have attached some images of the drivers. One is much worse. The speakers were located in an old and somewhat damp house, but not excessively so. I assume that the protective coating on the magnesium cones was not applied properly.
Well, it's very unfortunate but that's not a problem of how the coating had been applied. I can't believe it's formaldehyde though, you'd need a that high concentration of it to cause that, your friend would still be sitting beside the speakers, looking good, a bit dead but well preserved.

Now how did that happen? The coating is aluminium which builds up a oxide layer which protect itself and what's beneath or more precise, usually. It's still very close to the coast, 1km isn't much for the air. So the air is still humid from the sea and wind and with the humidity comes the salt. Salt and humidity corrodes the aluminium layer and after it's through, the magnesium can again happily corrode. Why is it worse on the inside? Well, light can't dry it up there, at least that's my theory.

You can clearly see that the corrosion is almost only on ONE side of the drivers (most likely on the back of the membrane on the other side than the front), I assume there was dust on which the salt and humidity could hold on and settle down to do it's 'work' (doesn't matter if sea-salt or formaldehyde). You can even still see a lot of dust on these sides.

I know such problems from a lot of PA systems in coast regions. Even the protective paint on wires (voice coil in compression drivers i.e.) or potentiometers, circuits etc. have a vastly shorter life. It's everywhere. The problem will persist with any other magnesium drivers, some may hold up a bit longer but the result in the end will be the same. Well, the drivers haven't been treated nicely, look at the dent in the voice coil of the worse driver, which touches the phase plug with negative excursion, the other one got a dent too, climate and treatment unfortunately add up.

I suggest, you'd build speakers which use different materials, i.e. aluminium 'lives' much longer in such situations but coated papercones are much better there.

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Originally Posted by Mardi View Post
I've just replaced the drivers with a L12s, and I realised i have used foam on the inner walls of the enclosure, about one inch thick that I got from an acoustic foam supplier. I wonder if the foam might release formaldehyde or something similar. Anyway, to be on the safe side, I have removed the foam and replaced it with the usual stuffing material.
John
Formaldehyde isn't used to produce foam, it's used in plastics for resin, hardener and so on. Foam needs opposite characteristics.
If formaldehyde is the cause, it comes from the enclosure. You'll have to build another enclosure then anyway since it will still continue to release the fumes (is that the right word?), that continues over 20-30 years.

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Originally Posted by eriksquires View Post
One other idea is a bag of rice! Rice is terribly absorbent (hydrophillic) and will help dry out the inside of the speaker in a couple of days.

Put it in a very porous cloth bag, or in a dish at the bottom.
That's a nice try but unfortunately futile. That only helps with the formaldehyde already in the air but not still within the enclosure wood.
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Old 17th December 2016, 06:04 AM   #23
Hartono is offline Hartono  Indonesia
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Originally Posted by eriksquires View Post
So I struck a little Google Gold! I searched for woofer corrosion and found an interesting thread. Bottom line was that the formaldehyde off-gassing inside the cabinets from the MDF was responsible for the crystals forming. More here:

Driver durability in hot & humid SG
wow nice info !
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Old 17th December 2016, 07:08 AM   #24
silverprout is offline silverprout  France
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Originally Posted by jkasch View Post
+1 Drivers shouldn't require Ziebart.
I've just auscultated my two W22EX001 , they are living since more than 10 years in a 60-90% humidity environment and they have no trace of oxidation at all.

Your membranes are defective, or your cabinets are releasing corrosive substances IMHO
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Old 17th December 2016, 08:35 AM   #25
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I've just auscultated my two W22EX001 , they are living since more than 10 years in a 60-90% humidity environment and they have no trace of oxidation at all.
You don't live at the ocean, do you?
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Old 17th December 2016, 03:18 PM   #26
eriksquires is offline eriksquires  United States
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My comment about the rice was for reducing humidity, not formaldehyde.

Sorry for the confusion,

Erik
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Old 17th December 2016, 03:36 PM   #27
silverprout is offline silverprout  France
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You don't live at the ocean, do you?
Actually 30Kms of the ocean and 5kms from the bigest river of my country but it is not the reason of my answer... but i've insinuated a chemical attack because because i've lived two years in a flat and for technical reasons, i was contraint to dry my washings in the living room.

The air saturation was contantly around 80-90% all days and nights and was often peaking at 98%... and they have endured this extreme conditions during two years without any trace of oxydation.

I've inspected my membranes today on both face (your post scared me) and the membranes are like new.
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Old 17th December 2016, 05:14 PM   #28
ICG is offline ICG  Germany
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Actually 30Kms of the ocean and 5kms from the bigest river of my country but it is not the reason of my answer... but i've insinuated a chemical attack because because i've lived two years in a flat and for technical reasons, i was contraint to dry my washings in the living room.

The air saturation was contantly around 80-90% all days and nights and was often peaking at 98%... and they have endured this extreme conditions during two years without any trace of oxydation.

I've inspected my membranes today on both face (your post scared me) and the membranes are like new.
If you really read my post, you surely understood that there is a protection layer which does in fact not react with the humidity, therefore the protection layer isn't destroyed by humidity and the real problem is the SALT.

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Originally Posted by eriksquires View Post
My comment about the rice was for reducing humidity, not formaldehyde.

Sorry for the confusion,

Erik
NP. But you have to remove the salt, not the humidity. Why? Magnesium itself builds a passivation layer too (like aluminium), which prevents oxidaton/corrosion. But once you get it out, the driver will be again exposed to the humidity and the salt can continue to destroy the passivation layer and it will immediately start again.

https://en.wikipedia.org/wiki/Passivation_(chemistry)
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Old 17th December 2016, 05:31 PM   #29
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If you really read my post, you surely understood that there is a protection layer which does in fact not react with the humidity, therefore the protection layer isn't destroyed by humidity and the real problem is the SALT.

Erh... i don't understand how the salt attacks the enclosed back side of the loudspeaker driver because the cone don't seem perforated.
Even in a bass reflex enclosure, the back side of the driver should be less attacked than the front side and the photos exhibit more corrosion on the back side.
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Old 17th December 2016, 07:03 PM   #30
ICG is offline ICG  Germany
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Erh... i don't understand how the salt attacks the enclosed back side of the loudspeaker driver because the cone don't seem perforated.
Even in a bass reflex enclosure, the back side of the driver should be less attacked than the front side and the photos exhibit more corrosion on the back side.
All gasses take up the volume and shape of the container, they spread out until they are evenly distributed (yes, that includes the air inside the speakers!). The humidity with it's salts is in the air aswell, as it's part of the gasses (air). If you take a bath, it's moisture everywhere, not only directly at the water. Why is it worse on the inside? In your bathroom you can see the behaviour of moisture very well at a cold mirror. I don't expect much of the moisture to condensate at the membrane, this is just to make it understandable why it's behaving this way. If you use a hair dryer with cold air (ofcourse even more with heat on) and point it to the clouded mirror, you will notice it will become quickly clear at the point the air is pointed at. In a room you have air movement, you move around, doors are opened, windows, a fan or radiator (heat) moves the air and so on. That is the effect of the hairdryer, it dries up quicklier. What's with the air inside the box? Well, it's protected from air movement because of the enclosure shielding it off. That means, the moisture on the surface isn't exposed to moving air which in turn means it stays longer moist.

I am pretty sure the driver which is better off was closer to air movement (door, window i.e.) and/or got more sunlight, which heats up the membrane (also on the back side because the metal is a fairly good heat conductor) and the moisture/salt mix can't settle down that well.

How likely is it it's formaldehyde? Not very likely. If it caused it, both drivers would be identical (at least on the inside) because both are in the same exposure of formaldehyde - unless both speakers are out of different material. And if that happens in just a year, the concentration of formaldehyde in the air is that extremely high, it would cause serious health problems, coughing, massive headaches, asthma and damaged organs.

What else can cause it? There are a variety of different things which contain chemicals which can damage the passivation layers, fumes of paint or paint thinner, bitumen, glue, spray cans, cleaning agent and so on. Also material which keep the moisture, especally close to the membrane, that means dust, damping material and so on. A special problem is the wood, especally MDF or particle board can keep a lot of moisture. If you put a MDF board with the edge into a bit of water you can observe it becomming sucked up, of all wood materials it soaks it up the best.
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