Hey guys.
I heard about this on another site and wanted ot know if anyone else had heard of anything like this.
Apparently, the old 1/72 DML hulls that they made of metal a few years back would "magically" disintegrate or fall apart after a period of time. It seems that there was some sort of instability or something reactive in the metal alloy that they used, and the metal hulls just can't be trusted--anyone hear of anything like this?
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Disintegrating DML metal hulls?
thedoog
Joined: May 14, 2007
KitMaker: 263 posts
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Posted: Sunday, April 12, 2009 - 04:14 PM UTC
Damraska
Joined: October 06, 2006
KitMaker: 580 posts
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Posted: Sunday, April 12, 2009 - 11:09 PM UTC
Quoted Text
Apparently, the old 1/72 DML hulls that they made of metal a few years back would "magically" disintegrate or fall apart after a period of time. It seems that there was some sort of instability or something reactive in the metal alloy that they used, and the metal hulls just can't be trusted--anyone hear of anything like this?
With regard to models, I have read about tracks that spontaneously decay, but never metals. Any material--metal, plastic, rubber, etc.--will break down if exposed to a reactive chemical. Perhaps someone accidentally used a corrosive paint or wash on the metal parts, thus causing the breakdown. My metal hull DML kits look fine after about 4 years (but still have sticky tracks--see below).
Older DS tracks found in those kits, molded in a black plastic, chemically react with enamel paints such that they never really dry. Acrylic paints do not cause this issue. In my experience, newer light tan DS tracks take both acrylics and enamels without issue.
Even if the hulls do react with some paint or wash chemical, avoiding the substance or using a good primer should prevent decay.
A very interesting question. If it it does happen, I will be very interested in the explanation.
-Doug
sabredog
Joined: July 22, 2007
KitMaker: 607 posts
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Posted: Wednesday, April 15, 2009 - 03:27 PM UTC
I only have a few of the DML metal hull kits. Not sure if I will build them as yet, however most certainly, metal needs something to react with it to corrode/disintegrate.
MacTrucks
Joined: November 12, 2006
KitMaker: 285 posts
Armorama: 228 posts
Posted: Wednesday, April 15, 2009 - 06:21 PM UTC
I've heard stories about the older DS tracks that are at the very least plausible. Paint not drying, disintegrating, all easily explained by reactions with paint or environmental factors.
Never heard of the diecast hulls disintegrating. I could see if someon exposed them to a caustic solution that it would be bad for the hulls, but simply painting them should not be. Maybe someone used a caustic primer thinking it would "bite" better into the metal. But under normal modelling use they should be stable.
Absolute worst case would be a diecast alloy that slowly oxidizes over time when unpainted surfaces are exposed to normal air. I've seen that in diecast cars but it is EXTREMELY rare and a case of something slipping through normal QC.
Never heard of the diecast hulls disintegrating. I could see if someon exposed them to a caustic solution that it would be bad for the hulls, but simply painting them should not be. Maybe someone used a caustic primer thinking it would "bite" better into the metal. But under normal modelling use they should be stable.
Absolute worst case would be a diecast alloy that slowly oxidizes over time when unpainted surfaces are exposed to normal air. I've seen that in diecast cars but it is EXTREMELY rare and a case of something slipping through normal QC.
Emeritus
Joined: March 30, 2004
KitMaker: 2,845 posts
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Posted: Wednesday, April 15, 2009 - 10:13 PM UTC
I've heard of that too. IIRC, someone posted photos in a thread on track-link.net. Looked scary, cracked and crumbling to pieces. It was speculated to be from a faulty batch of hulls where the manufacturer somehow got the diecast formula messed up.
Damraska
Joined: October 06, 2006
KitMaker: 580 posts
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Posted: Thursday, April 16, 2009 - 05:29 AM UTC
Quoted Text
I've heard of that too. IIRC, someone posted photos in a thread on track-link.net. Looked scary, cracked and crumbling to pieces. It was speculated to be from a faulty batch of hulls where the manufacturer somehow got the diecast formula messed up.
Here is the thread on Track-link:
http://www.track-link.net/forum/modelling_smallscale/4159
Which leads to this interesting thread on Missing-lynx:
http://www.network54.com/Forum/47210/message/1231501461/dragon+metal+parts....!!!!
Which leads to these explanations of Zinc Pest and Tin Pest from the Wikipedia:
http://en.wikipedia.org/wiki/Zinc_pest
http://en.wikipedia.org/wiki/Tin_pest
So, it turns out that alloys of zinc and tin, under the right conditions of concentration, temperature, humidity, and exposure to air, can break down and eventually disintegrate. For zinc, lead contamination serves as the primary catalyst. For tin, cold temperatures trigger a natural change in the molecular structure of the metal.
Based on my reading, I believe lead contamination ruined those DML hulls. Lead naturally contaminates many alloys. When melted, lead sinks to the bottom of the liquid metal. Lead impurities thus concentrate at the bottom of a pour cup. Normally, manufacturers throw out the poor quality slag at the bottom of a pour cup. In this case, it was apparently used to cast a few more hulls.
If anyone knows more about this fascinating process, please feel free to correct me or elaborate!
-Doug
Sabot
Joined: December 18, 2001
KitMaker: 12,596 posts
Armorama: 9,071 posts
KitMaker: 12,596 posts
Armorama: 9,071 posts
Posted: Thursday, April 16, 2009 - 05:40 AM UTC
I've got several of the metal hulled kits, but have only built three of them (Sturmtiger, Panther G early, Jagdpanther). I haven't had the metal break down on the built kits that I've noticed. I have not looked in the unbuilt kits in years and couldn't tell if they are still in one piece or not.
thedoog
Joined: May 14, 2007
KitMaker: 263 posts
Armorama: 260 posts
Posted: Thursday, April 16, 2009 - 06:14 AM UTC
Quoted Text
Doug, thanks for that excellent, informative post, and the attached links! I have a couple metal hulled early DML kits, but I'll forgo the risk of building them and just try to reacquire them in plastic. This is a great source of info on the whole matter!Quoted TextI've heard of that too. IIRC, someone posted photos in a thread on track-link.net. Looked scary, cracked and crumbling to pieces. It was speculated to be from a faulty batch of hulls where the manufacturer somehow got the diecast formula messed up.
Here is the thread on Track-link:
http://www.track-link.net/forum/modelling_smallscale/4159
Which leads to this interesting thread on Missing-lynx:
http://www.network54.com/Forum/47210/message/1231501461/dragon+metal+parts....!!!!
Which leads to these explanations of Zinc Pest and Tin Pest from the Wikipedia:
http://en.wikipedia.org/wiki/Zinc_pest
http://en.wikipedia.org/wiki/Tin_pest
So, it turns out that alloys of zinc and tin, under the right conditions of concentration, temperature, humidity, and exposure to air, can break down and eventually disintegrate. For zinc, lead contamination serves as the primary catalyst. For tin, cold temperatures trigger a natural change in the molecular structure of the metal.
Based on my reading, I believe lead contamination ruined those DML hulls. Lead naturally contaminates many alloys. When melted, lead sinks to the bottom of the liquid metal. This tends to concentrates lead impurities at the bottom of a pour cup. Normally, manufacturers throw out the poor quality slag at the bottom of a pour cup. In this case, it was apparently used to cast a few more hulls.
If anyone knows more about this fascinating process, please feel free to correct me or elaborate!
-Doug
Sounds like DML was trying to squeeze a couple more peenies from that slag?
Damraska
Joined: October 06, 2006
KitMaker: 580 posts
Armorama: 499 posts
Posted: Thursday, April 16, 2009 - 06:45 AM UTC
Quoted Text
Doug, thanks for that excellent, informative post, and the attached links! I have a couple metal hulled early DML kits, but I'll forgo the risk of building them and just try to reacquire them in plastic. This is a great source of info on the whole matter!
You are very welcome. If you have a contaminated hull, I believe it would show signs of decay by now. From my research I gather that the lead content must rise above some critical concentration (percentage of the alloy) for the reaction to start and high humidity helps get the process going. You are probably okay but the plastic hulls are easier to work with. I much prefer them.
Quoted Text
Sounds like DML was trying to squeeze a couple more peenies from that slag?
I wonder if DML cast their own metal hulls or farmed it out. Collectors of Dragon Armor really have something to worry about!
-Doug
Belt_Fed
Joined: February 02, 2008
KitMaker: 1,388 posts
Armorama: 1,325 posts
Posted: Thursday, April 16, 2009 - 07:14 AM UTC
You're right Karl. I bought a DML Panther kit with a metal bottom hull. As i was removing the hull from the packaging, the sponsons just cracked off under my fingers. The idler wheel mounts stood up no better. Not only that, the fit of the part was terrible. I obviously said a few choice words and was quite upset 
thedoog
Joined: May 14, 2007
KitMaker: 263 posts
Armorama: 260 posts
Posted: Thursday, April 16, 2009 - 01:40 PM UTC
Doug, I never thought about that--DML "farming out" the casting work? Hmm. I wonder what percentage of these metal hulls bit the dust?
Sorry to hear of your misfortune, Jon--I woulda been seriously bummed too!
Sorry to hear of your misfortune, Jon--I woulda been seriously bummed too!
pasdj002
Joined: April 20, 2009
KitMaker: 113 posts
Armorama: 102 posts
Posted: Tuesday, April 21, 2009 - 03:40 PM UTC
First Post 
Hey guys, happened to my DML Panther G. I stuffed up a coat of Tamiya Acrylic on the lower hull.
Cleaned with Windex, and as i scrubbed it, noticed all the wheel mounts had fallen off....:O
I was so annoyed i threw it on the ground. I was expecting for it to basically land on the carpet ( while at the same time thinking, okay i will drill some holes in and place rod for each wheel mount).
To my surprise the hull split in half, and at the edges crumbled :O
I picked it up and noticed that the Grey original metal primer had hundreds of little cracks. I could literally flick my finger at the hull and see fragments fly off :O.
But yes, not a nice experience. All i got left now is the hull top, which seems to be okay, and the turret components.
Damian
Hey guys, happened to my DML Panther G. I stuffed up a coat of Tamiya Acrylic on the lower hull.
Cleaned with Windex, and as i scrubbed it, noticed all the wheel mounts had fallen off....:O
I was so annoyed i threw it on the ground. I was expecting for it to basically land on the carpet ( while at the same time thinking, okay i will drill some holes in and place rod for each wheel mount).
To my surprise the hull split in half, and at the edges crumbled :O
I picked it up and noticed that the Grey original metal primer had hundreds of little cracks. I could literally flick my finger at the hull and see fragments fly off :O.
But yes, not a nice experience. All i got left now is the hull top, which seems to be okay, and the turret components.
Damian
sabredog
Joined: July 22, 2007
KitMaker: 607 posts
Armorama: 599 posts
Posted: Tuesday, April 21, 2009 - 09:33 PM UTC
Crikey.
I am halfway through that kit now....
I am halfway through that kit now....
Valsmere
Joined: March 10, 2009
KitMaker: 13 posts
Armorama: 12 posts
Posted: Saturday, April 25, 2009 - 03:03 PM UTC
This was covered in an earlier post in this thread, zinc pest. It is a problem in some of the early Marklin HO scale trains. It has something to do with humidity and storage along with the composition of the metal (alloy) in the casting. As far as I know there is no cure. At one time, a few years ago, I had stumbled upon a rumor that there is/ was a cure but I think it was proven false. Sorry I couldn't be of more help.
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