K-Line couplers falling apart

I had a few where the couplers broke off and sideframes crumbled.

I think the are only available as one assembly.  Were not available at Brasseur's at the time. 

It took some time finding them a a decent price...

John,  Which cars have the self-destruct couplers.  Early from sets with baggage cars whose doors do not slide, later sets whose baggage cars doors slide, cars with overhead lighting, cars with overhead lighting and interiors?  Replacement trucks with couplers are available from individuals at $30-$40 per pair.  Williams trucks may be used as replacements.  Two rail modelers have no use for K-Line three axle three rail trucks.  Respectfully, John in Lansing, ILL

Perhaps we might have a metal expert in OGR Forum land that can help.    I have seen this several times but none of my own.  I have many of these cars.  My train room is the same temp year round.  I have wondered if temp changes may play a part.  I do not know.  I have seen it on some MTH smoke units.  Many couplers and Lionel passenger side frames.   Guys, I am only throwing this out as a thought.  

John, I am sure any of the parts guys who advertise on the Forum can help you.   If you have no luck, the next time you are at my house you can go through my parts.

It sounds like pest; crumbly, powdery, like dried alkaline corrosion.

    I would consider a full change to a new brand of truck since any originals for them actually stand a chance of doing the same thing. (Ive also heard the Broadway limiteds were bad for it, but havent seen one yet, and mine are perfect) I don't think anything stops or slows it; impurities in the metal is doing it. Maybe extreme dry & cold would help, but expansion stresses from temp changes could cause things to break away even sooner too.

Basically its impurities in the zinc alloy that leads to intergranular corrosion of the alloy.  I had this happen on the side trucks of my JLC GG-1.  It is accelerated by moisture, as is most corrosion, and high temperatures.  So cool dry areas will have slower corrosion rates.  So more than likely there were still quality control problems that did not minimize these impurities or used zinc alloys that were more susceptible to this intergranular corrosion.  Good write up in Wikipedia and look at the attached file if you want more details.  As  you can tell, I'm a metallurgist.   

WIkipedia

Zinc pest (from German Zinkpest), also known as zinc rot, is a destructive, intercrystalline corrosion process of zinc alloys containing lead impurities.^[1] While impurities of the alloy are the primary cause of the problem, environmental conditions such as high humidity (greater than 65%) may accelerate the process.^[2][3]

It was first discovered to be a problem in 1923,^[1] and primarily affects die-cast zinc articles that were manufactured during the 1930s, 1940s, and 1950s. The New Jersey Zinc Company developed zamak alloys in 1929 using 99.99% pure zinc metal to avoid the problem, and articles made after 1960 are usually considered free of the risk of zinc pest since the use of purer materials and more controlled manufacturing conditions make zinc pest degradation unlikely.^[2]

Affected objects may show surface irregularities such as small cracks and fractures, blisters or pitting. Over time, the material slowly expands, cracking, buckling and warping in an irreversible process that makes the object exceedingly brittle and prone to fracture, and can eventually shatter the object, destroying it altogether. Due to the expansion process, attached normal material may also be damaged. The occurrence and severity of zinc pest in articles made of susceptible zinc alloys depends both on the concentration of lead impurities in the metal and on the storage conditions of the article in the ensuing decades. Zinc pest is dreaded by collectors of vintage die-cast model trains, toys, or radios, because rare or otherwise valuable items can inescapably be rendered worthless as the process of zinc pest destroys them. Because castings of the same object were usually made from various batches of metal over the production process, some examples of a given toy or model may survive today completely unaffected, while other identical examples may have completely disintegrated. Since the 1940s, some model railroad hobbyists have claimed, with varying degrees of success, that a method of "pickling" zinc alloy parts by soaking them in vinegar or oxalic acid solution for several minutes before painting and assembling them could prevent or delay the effects of zinc pest. Engine parts of older vehicles or airplanes, and military medals made of zinc alloys may also be affected.

Zinc pest is different from a superficial white oxidation process ("Weissrost") that may affect some zinc articles, and is not related to tin pest.

Thanks guys--the cars in question are the NYC 20th Century Limited Heavyweights (one car is numbered 1186). I took my K-Line NYC 28th Anniversary set off the shelf and looked at those couplers. They appear to be holding up very well, but also look like they're made of a different material--and they have a shinier finish to them. This is my first experience with zinc pest, and I'm glad it's with modern couplers and not one of my prized prewar trains! The search goes on for replacements.

John

I've also read, on these forums, about some K-Line GG1s having the same issue with the motor truck side frames.  Short of actually seeing the disintegration happening, is there any way to know if the locos I have would be a candidate for Zinc pest ?

rattler21...do you have the part number for the Williams by bachman trucks?