patina on the cone?

rick57 · 24th August 2006, 12:58 PM

What could cause a patina on the front and rear surfaces of driver cones (SEAS mag cones) ?

Don't know how clear these are:

http://img.photobucket.com/albums/v3...S/photo023.jpg

http://img.photobucket.com/albums/v3...S/photo021.jpg

Thanks

Virtalahde · 24th August 2006, 01:11 PM

Looks like oxidation to me.

rick57 · 24th August 2006, 01:22 PM

That's what I was thinking. Er what effect might that on the sound ~ presumably not good (by much??)

Cheers

FullThrottleRic · 24th August 2006, 02:19 PM

zero to none

rick57 · 25th August 2006, 07:25 AM

FullThrottleRic, or anyone

are you sure - sounds odd to me?

cheers

Will · 25th August 2006, 07:38 AM

Go claim warranty !

badman · 25th August 2006, 01:32 PM

I'd anticipate extremely small influence on sound (probably none)- the surface texture hasn't changed significantly, nor should the mechanical properties of the cone.

angsuman · 25th August 2006, 05:01 PM

So there are bits of oxidation on the cone? How could that happen? Is magnesium prone to oxidation? What about other metal cones, such as aluminum how prone are they to oxidation?

mrshow4u · 25th August 2006, 05:05 PM

It doesn't look like any problem at all.

Quote:

What about other metal cones, such as aluminum how prone are they to oxidation?

Aluminum oxidizes as soon as it is in air. Anodizing it will seal it, though

lne937s · 26th August 2006, 05:05 PM

When Magnesium oxidizes, much like aluminum, it creates a thin layer of oxidation. The oxides of magnesium and aluminum are ceramic and prevent further oxidation (why aluminum doesn't "rust").

Unless you are welding or making electrical connections, it is perfectly normal and fine. The thin layer of oxidation will prevent further oxidation better than any paint covering of the same thickness and weight. Therefore, it is probably best just to leave it unless the aesthetics bother you.

I think some companies actually advertise the thin layer of ceramic oxidation as being beneficial (Klipsch on their aluminum cones?).

If the layer of oxidation becomes more than just a patina, there is probably some sort of chemical on the cones causing that oxidation, which needs to be removed.

Magnesium is very reactive- just try placing it acid or setting it on fire (violent exothermic oxidation)- but that thin layer of ceramic oxidation keeps it from rusting through. It should be fine for a speaker cone.

24th August 2006, 12:58 PM	#1
rick57 diyAudio Member Join Date: Dec 2002 Location: dry ol Melbourne Australia	patina on the cone? What could cause a patina on the front and rear surfaces of driver cones (SEAS mag cones) ? Don't know how clear these are: http://img.photobucket.com/albums/v3...S/photo023.jpg http://img.photobucket.com/albums/v3...S/photo021.jpg Thanks

25th August 2006, 01:32 PM	#7
badman Custom Title diyAudio Member Join Date: Sep 2003 Location: Sunny Tustin, SoCal	I'd anticipate extremely small influence on sound (probably none)- the surface texture hasn't changed significantly, nor should the mechanical properties of the cone. __________________ I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!

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24th August 2006, 01:11 PM	#2
Virtalahde diyAudio Member Join Date: Jan 2006 Location: Kuhmoinen, Finland	Looks like oxidation to me.

24th August 2006, 01:22 PM	#3
rick57 diyAudio Member Join Date: Dec 2002 Location: dry ol Melbourne Australia	That's what I was thinking. Er what effect might that on the sound ~ presumably not good (by much??) Cheers

24th August 2006, 02:19 PM	#4
FullThrottleRic diyAudio Member Join Date: Apr 2001 Location: Leeds, UK	zero to none

25th August 2006, 07:25 AM	#5
rick57 diyAudio Member Join Date: Dec 2002 Location: dry ol Melbourne Australia	FullThrottleRic, or anyone are you sure - sounds odd to me? cheers

25th August 2006, 07:38 AM	#6
Will diyAudio Member Join Date: Sep 2001 Location: Kuala Lumpur	Go claim warranty !

25th August 2006, 05:01 PM	#8
angsuman diyAudio Member Join Date: Mar 2005 Location: Las Vegas NV	So there are bits of oxidation on the cone? How could that happen? Is magnesium prone to oxidation? What about other metal cones, such as aluminum how prone are they to oxidation?

26th August 2006, 05:05 PM	#10
lne937s diyAudio Member Join Date: Dec 2004 Location: New York City	When Magnesium oxidizes, much like aluminum, it creates a thin layer of oxidation. The oxides of magnesium and aluminum are ceramic and prevent further oxidation (why aluminum doesn't "rust"). Unless you are welding or making electrical connections, it is perfectly normal and fine. The thin layer of oxidation will prevent further oxidation better than any paint covering of the same thickness and weight. Therefore, it is probably best just to leave it unless the aesthetics bother you. I think some companies actually advertise the thin layer of ceramic oxidation as being beneficial (Klipsch on their aluminum cones?). If the layer of oxidation becomes more than just a patina, there is probably some sort of chemical on the cones causing that oxidation, which needs to be removed. Magnesium is very reactive- just try placing it acid or setting it on fire (violent exothermic oxidation)- but that thin layer of ceramic oxidation keeps it from rusting through. It should be fine for a speaker cone.

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