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Offline guss-tav  
#1 Posted : 17 December 2008 19:56:10(UTC)
guss-tav


Joined: 01/04/2007(UTC)
Posts: 70
Location: ,
Hello,

When the process of Zinkpest is started on a model, does it continue to develop itself despite of good conditions of preservation?

Thanks for your informations.

Best regards,

Jean
Offline Unholz  
#2 Posted : 17 December 2008 19:59:50(UTC)
Unholz

Switzerland   
Joined: 29/07/2007(UTC)
Posts: 1,211
Location: Switzerland
Yes - if it is actually Zinkpest, there seems to be no known method of stopping the process once it has started.
Offline TTRExpress  
#3 Posted : 17 December 2008 21:15:28(UTC)
TTRExpress

United States   
Joined: 06/04/2006(UTC)
Posts: 655
"Zinkpest" is an incurable disease that hopefully should now be eliminated from modern locomotives. Zinc pest is a form of intercrystalline corrosion. The process is accelerated by moisture in warm air and relative humidities of 65% or greater. Hydrogen released from water migrates into the grain boundaries of the zinc alloy and causes expansion which results in cracking along those grain boundaries.

Zinc can be alloyed with aluminum, magnesium, copper, lead and cadmium usually at levels less than 1%. Larger concentrations of iron, lead, cadmium and tin could have an adverse effect on corrosion resistance, which results in structural weakening of the die casting.

Two types of zinc alloy were developed. In the 1920's, ZAMAK (zinc-aluminum-magnesium-copper) and in the 1970's ZA (zinc-alumunium) were produced. The ZAMAK contains about 4% aluminum and are identified by their numbers 3,5 and 7.

Maerklin uses ZAMAK 410 which is like ZAMAK 3 or 5. ZAMAK 3 and 5 differ by the addition of 1% copper to the 5 to make it more ductile.

Permitted additives (= aimed added metals to reach around certain material properties) in cast alloys ZAMAK 3: Aluminum 3.8 to 4.3% copper up to 0,03% magnesium 0.03 to 0,06%.

Permitted impurities (= which one can still tolerate at impurities to hold around the costs of the production in the framework): Iron max. 0.1% nickel max. 0.02% manganese max. 0.01% lead max. 0.005% cadmium max. 0.005% tin max. 0,003%

Data suggests that higher levels of copper and lead in the zinc alloy aid the degradation. High levels of aluminum can cause oxidation to occur leading to rust.

Some people regard tin pest as the actual cause of zinc pest. With tin pest pure metallic beta-tin is converted below 13,2°C into non-metallic alpha-tin. Energy becomes free and the density falls, i.e. the volume grows. Because the content of tin is well under 1%, then the volume in the zinc alloy to cause zinc pest alone by tin is not really substantiated.

A comprehensive treatise on zinc pest is given by Peter Berg at
http://www.tischeisenbahn.de/Restauri/page4.htm
Regards (a Scot in Wisconsin),

Maurice [ETE, TTRCA, IG-TRIX Express, Maerklin-Insider & TRIX Profi-Club]
Offline guss-tav  
#4 Posted : 18 December 2008 21:10:29(UTC)
guss-tav


Joined: 01/04/2007(UTC)
Posts: 70
Location: ,
Hello,
Thanks at you both for your answer. Very instructive. And thanks for the link.
Best regards,
Jean
Offline jvuye  
#5 Posted : 19 December 2008 09:07:16(UTC)
jvuye

Belgium   
Joined: 01/03/2008(UTC)
Posts: 2,847
Location: South Western France
Hi
One little addition Maurice's explanation: hydrogen from "water" into the structure via formation of sulfuric acid, that form from the mixture of Sulphur residue that first combines with Oxygen (SO2, SO3° which turns into H2SO" or H2So4 by hydrolysis, and starts the process.
I had noticed that pieces that had a perfect original paint job, were less prone/ less infected with Zinkpest
So if one has a chance to seal perfectly the surface and keep it that way, one can slow down or stop the degradation.
I have done this on a 1947 CCS 800 Crocodile (my avatar) which has been in my possession since 1959.
The chassis had already been attacked then (no/little paint).
Under advice of my chemistry teacher, I coated the inside of the body and the rest of the chassis with a clear varnish that sealed the cracks.
The paint job on the outside was perfect, so I did not touch it.
I don't clain it is a cure...but the CCS 800 is still looking like new today!
For what it is worth.
Jacques Vuye aka Dr.Eisenbahn
Once a vandal, learned to be better and had great success!
Offline guss-tav  
#6 Posted : 22 December 2008 19:56:56(UTC)
guss-tav


Joined: 01/04/2007(UTC)
Posts: 70
Location: ,
Hello Mr Vuye, thank you for your observation and advice.
Jean
Offline shaygetz  
#7 Posted : 23 December 2008 01:38:25(UTC)
shaygetz


Joined: 19/12/2006(UTC)
Posts: 348
Location: , Florida
The frame of my Rivarossi 4-8-8-2 Cab-forward was badly warped and cracked with zinc pest when I bought it. I broke it into 3 pieces and glued it together flat and level with J-B Weld. Once hardened, I filed it smooth, then painted it with a heavy coat of enamel. The repair is now 5 years old and shows no sign of further damage.

I wish I could say the same for my 346/1 coach...sigh...

UserPostedImage

"To escape the error of salvation by works we have fallen into the opposite error of salvation without obedience.”

---A.W. Tozer

Webpage... www.freewebs.com/shaygetz
Blog... http://misterbobsmodelworksemporium.blogspot.com/
Offline hgk  
#8 Posted : 23 December 2008 08:54:15(UTC)
hgk


Joined: 10/11/2006(UTC)
Posts: 455
Location: Pacific Ocean
Jean,
Here's a tiny bit of information-
http://www.liverpoolmuse...ore/red_black_coupe.aspx
Regards,
George

Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by guss-tav
<br />Hello,

When the process of Zinkpest is started on a model, does it continue to develop itself despite of good conditions of preservation?

Thanks for your informations.

Best regards,

Jean
Offline davpadlee  
#9 Posted : 28 December 2008 05:17:31(UTC)
davpadlee


Joined: 19/10/2008(UTC)
Posts: 76
Location: Vallejo, CA
You can get replacement wheels from Ritter Restaurations
in Germany.
I got some for my 374 prewar tanker and plan on ordering more.
They have parts for many items from the 1930's up to the 50's
They also accept Paypal.
Best Davebiggrinbiggrin
Offline guss-tav  
#10 Posted : 28 December 2008 13:19:41(UTC)
guss-tav


Joined: 01/04/2007(UTC)
Posts: 70
Location: ,
Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by hgk
<br />Jean,
Here's a tiny bit of information-
http://www.liverpoolmuse...ore/red_black_coupe.aspx
Regards,
George

Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by guss-tav
<br />Hello,

When the process of Zinkpest is started on a model, does it continue to develop itself despite of good conditions of preservation?

Thanks for your informations.

Best regards,

Jean



Thank you for this complement George.
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