Author Topic: Preventing neoprene off-gassing?  (Read 3197 times)

Offline Brinybay

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Preventing neoprene off-gassing?
« on: October 24, 2013, 04:24:58 PM »
I was just looking at one of my phones that has round neoprene feet with some rust from the neoprene off-gassing.  Even when I remove the rust, I'm wondering what's going to happen several years or decades down the road.  Is there a way to prevent more off-gassing from neoprene feet?  Also, what's the best way to get the rust off?
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Offline jsowers

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Re: Preventing neoprene off-gassing?
« Reply #1 on: October 24, 2013, 04:41:27 PM »
Instead of out-gassing, would it just be that Neoprene attracts moisture and the areas around the feet rust when in a damp environment? If that's the case, then keeping it in a dry place would be important. I know someone who buys large Ziploc bags and puts restored phones in them. I'm not so sure about that. A little air circulation may be good. But what do I know? I am no scientist.

I know we see these phone feet with and without rust, so all of them didn't rust. So is it just the ones that were in a damp basement or humid part of the country that rusted? It's hard to tell.

I do recall seeing the evidence of the out-gassing of the rubber parts inside on the ringer mounts making brown stains on NOS soft plastic phones, sometimes all the way through the plastic. It didn't seem to happen on phones that were installed. Just ones that stayed in the box in a more or less closed environment.

I'll leave the how-to on rust removal to others who have done it. I leave mine rusty.
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unbeldi

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Re: Preventing neoprene off-gassing?
« Reply #2 on: October 24, 2013, 05:25:58 PM »
Interesting topic, and while having observed this and looked for literature,  I have not been able to form a final opinion why this happens, because some phones seem to be doing just fine with their neoprene feet while others look horrible.

I have never heard that neoprene attracts moisture any more than other materials. But water sticks to many surfaces very well, so why it would cause rusting in the areas surrounding the feet is not clear to me.  Sometimes I have noticed that the rust cover seems to get thinner with the distance from the feet, fading out.  This seems to give some credence to the outgassing hypothesis.

Neoprene is known to break down due to a variety of causes. Many household liquids, such as cleaners, acid, facilitate degradation, as can temperature and weather influences. It is a polymer of a chlorinated hydrocarbon, with sulphur atoms or clusters linking the monomers.
So, prominent degradation products would be hydrogen chloride (HCl), sulfur dioxide (SO2), and some other organic acids, all strong corrosion agents. Particularly HCl and SO2, both gases, form hydrochloric and sulfuric acid, when combined with water. In nature this process has become infamous as acid rain. I can understand that HCl, in humid environments, would deposit on the metal around the feet. In the presence of any amount of water film adhered on the surface, it immediately dissolves and disassociates into the acid.

Rust is probably most effectively treated with phosphoric acid, which also leaves a protective phosphate cover on the metal. However, this cover is porous, and commercial rust treatments include compounds to smoothen the phospate layer to prevent moisture penetration.

I think that once an onset of rust has developed for whatever reason it will only continue to grow and worsen. It is unavoidable for water being absorbed from the atmosphere feeding the rusting reaction until the metal is gone, unless it is properly treated and stopped. This is why base surfaces were painted or, later, cadmium plated.
« Last Edit: October 24, 2013, 05:55:27 PM by unbeldi »

unbeldi

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Re: Preventing neoprene off-gassing?
« Reply #3 on: October 24, 2013, 09:41:23 PM »
I just noticed in another current thread this effect of rust fading with the distance from the Neoprene feet:  http://www.classicrotaryphones.com/forum/index.php?action=dlattach;topic=10370.0;attach=59753;image

This is a 5302 that was retrofitted with 500-series Neoprene feet.

Offline Brinybay

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Re: Preventing neoprene off-gassing?
« Reply #4 on: October 25, 2013, 04:06:11 AM »
I just noticed in another current thread this effect of rust fading with the distance from the Neoprene feet:  http://www.classicrotaryphones.com/forum/index.php?action=dlattach;topic=10370.0;attach=59753;image

This is a 5302 that was retrofitted with 500-series Neoprene feet.

Yes, that's the 5302 I just bought.  That's what made me check out my other phones that had neoprene feet.
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Offline TelePlay

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Re: Preventing neoprene off-gassing?
« Reply #5 on: October 25, 2013, 07:47:37 PM »
I'm thinking a combination of long term phone placement and climatic conditions. That is, a phone placed such that it cools and is below the dew point as humidity increases around the phone causing condensation to collect around the feet affecting the metal. For example, the phone with only 2 feet rusted could have been next to a colder outside wall for a long period of time. Just a little collected moisture every day for years may/could do that. Or, I may just be all wet on that theory.
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Offline WEBellSystemChristian

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Re: Preventing neoprene off-gassing?
« Reply #6 on: October 27, 2013, 11:04:18 PM »
Has anyone thought of the possibility of Galvanic Corrosion? Maybe it's not the plastic feet that are causing the rust, maybe it's the rivets that hold them to the base. Here are 2 articles on Galvanic Corrosion:
http://en.wikipedia.org/wiki/Galvanic_corrosion

http://corrosion-doctors.org/Forms-galvanic/galvanic-corrosion.htm
« Last Edit: October 27, 2013, 11:07:08 PM by WEBellSystemChristian »
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Offline Kenton K

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Re: Preventing neoprene off-gassing?
« Reply #7 on: October 28, 2013, 02:18:10 AM »
Has anyone thought of the possibility of Galvanic Corrosion? Maybe it's not the plastic feet that are causing the rust, maybe it's the rivets that hold them to the base. 

I believe that leather 302 feet are galvanized, and the galvanized part is in direct contact with the metal base. And none of the 302 I have encountered have the rust.

I also believe that many parts in the 302 are galvanized. For instance I believe that most 5H dials, condenser clasps, network supports, and screws are galvanized. And I have never seen much rust concentrated around them.

So I believe that the rubber feet is the problem along with the environment. I have two same date 500s, one with rust and another without. The one with rust was the pool phone and had lived outside for the past 10+ years. The one without rust I believe is practically mint. Correct me if I am wrong, but I believe it is moisture that causes rust

Offline Brinybay

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Re: Preventing neoprene off-gassing?
« Reply #8 on: October 28, 2013, 03:25:43 AM »
Somewhere in my travels in the phone collecting world, I read that the feet were made of neoprene, which off-gasses as it ages, causing corrosion.  I never fact-checked that, just assumed it was accurate, maybe it isn't.
The idea that a four-year degree is the only path to worthwhile knowledge is insane.
 - Mike Row
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