Is this zinc pest?

Yes, even though I am new to the hobby, I was warned by friends that there was a period of MTH cars known to have zinc pest prone couplers. I consider your picture an example picture I'll use for future reference. FWIW, I just saw zinc pest on a K-line boxcar still in the original box- it plagued the industry.

https://ogrforum.com/...ilure-degraded-metal

https://ogrforum.com/...ssenger-car-couplers

It doesn’t look good. I have a set of MTH Premier coaches from around 1999 and the entire five car set needed new couplers. They didn’t have as much surface corrosion, but the coupler armature would snap right off with minimal force. The knuckles would also snap.

I believe you can contact MTH and they will replace the couplers for free. Replace them all if they have the corrosion on them.

the new, replacement, couplers have a stamped steel armature not cast like the defective couplers...

Tom

WOW, time for a new coupler!   It looks like it's just the coupler arm that's affected.

That looks more like corrosion from a wet environment than zinc pest. Normally, zinc pest is characterized by swelling and a pattern of cracks on the affected item.

While that corrosion looks bad, it does not usually affect the structural strength of the metal although it damages the surface. Wire brushing will remove some of it.

Zinc pest:

Jim

Thanks Jim because MTH is firm about nothing being warranted after five years. I will try a wire brush wheel on a Dremel. The coupler glad hands and arms seem to be very solid but frozen and nonfunctional.  I'll try the wire wheel first, then soak them in brake fluid to see if that frees them up. The only thing I ever owned with ZP was the infamous Weaver Troop Cars. Your pictures really helped me out...Rich

Jim Policastro posted:

That looks more like corrosion from a wet environment than zinc pest. Normally, zinc pest is characterized by swelling and a pattern of cracks on the affected item.

While that corrosion looks bad, it does not usually affect the structural strength of the metal although it damages the surface. Wire brushing will remove some of it.

Zinc pest:

Jim

Jim, I have parts which looked like these for years and when replacements  are not available I used water thin CA glue to fill and seal those crevices and it seems to stabilize the part. Not a perfect solution but a solution none the less.  cyanoacrylate glues are hygroscopic "water seeking" and will bind with water molecules in the joints and seal air out, greatly slowing the electrolysis.          j

Looks more like a reaction of some type of die lubricant.  Similar to the white film that appears on many Gilbert AF vintage pieces.  Or perhaps stored in a manner where the couplers got cold in a humid environment.

Jim,

I agree whole heartedly with your assessment. Spot on!

John, While the water thin ACC glue is a good idea, it will not stop the corrosion from continuing. The problem is what is in the alloy: Too much lead! And it permeates the entire casting. So you can apparently slow the effect down, but in reality, it just keeps going. Eventually the only thing holding the casting together will be the glue. Everything else will be dust. And the problem is NOT limited to one brand of train ! ALL of them have had it at one time or another. The source of the problem is  currently in China, where most of not all these castings are made. They use little mom and pop foundries (for lack of a better term) that neither know nor care what goes into the melt so long as it goes in. Zinc alloys are VERY particular about the amount of lead in the melt. and it does not take much to ruin the entire batch. The good news is, the process is batch driven, so the next batch can be perfectly fine. It's all about the QC of the melt.

Chris

LVHR

Jim's spot on!

lehighline posted:

Jim,

I agree whole heartedly with your assessment. Spot on!

John, While the water thin ACC glue is a good idea, it will not stop the corrosion from continuing. The problem is what is in the alloy: Too much lead! And it permeates the entire casting. So you can apparently slow the effect down, but in reality, it just keeps going. Eventually the only thing holding the casting together will be the glue. Everything else will be dust. And the problem is NOT limited to one brand of train ! ALL of them have had it at one time or another. The source of the problem is  currently in China, where most of not all these castings are made. They use little mom and pop foundries (for lack of a better term) that neither know nor care what goes into the melt so long as it goes in. Zinc alloys are VERY particular about the amount of lead in the melt. and it does not take much to ruin the entire batch. The good news is, the process is batch driven, so the next batch can be perfectly fine. It's all about the QC of the melt.

 

Chris

LVHR

OK Chris,  don't think I said it would stop the corrosion?   I think I said it would greatly slow the electrolysis, which it does.  I have zinc wheels on prewar locos that look like a spider web but have not deteriorated further since a CA bath.  The current lead problem is common knowledge you do business with the chinese and this is what you get.  The worst mistake this country ever made was selling, I mean giving,  china "Most Favored Nation" status.    I just happen to have a photo handy of a MTH smoke unit which I took out of a MTH 20-3029-1  SP Daylight loco that I bought new in 1999,by 2002 I had to replace it.  The bottom of the blower cage and the motor fell out.  I decided to see if I could save the thing and made a new bottom out of plastic and doused the rest of the casting in CA. Well, that was at least 16 years ago.  I pulled it out of a box of parts  a couple of months ago and it has not deteriorated to any noticeable extent since I washed it in CA. Though it is swollen a full 1/8" wider than original it seems solid and works fine.  So I put it in a Lionel 18000 B6 switcher when I added TMCC this summer.  As I said it's not a perfect solution but a solution none the less.           j

JohnActon posted:

lehighline posted:

Jim,

I agree whole heartedly with your assessment. Spot on!

John, While the water thin ACC glue is a good idea, it will not stop the corrosion from continuing. The problem is what is in the alloy: Too much lead! And it permeates the entire casting. So you can apparently slow the effect down, but in reality, it just keeps going. Eventually the only thing holding the casting together will be the glue. Everything else will be dust. And the problem is NOT limited to one brand of train ! ALL of them have had it at one time or another. The source of the problem is  currently in China, where most of not all these castings are made. They use little mom and pop foundries (for lack of a better term) that neither know nor care what goes into the melt so long as it goes in. Zinc alloys are VERY particular about the amount of lead in the melt. and it does not take much to ruin the entire batch. The good news is, the process is batch driven, so the next batch can be perfectly fine. It's all about the QC of the melt.

 

Chris

LVHR

OK Chris,  don't think I said it would stop the corrosion?   I think I said it would greatly slow the electrolysis, which it does.  I have zinc wheels on prewar locos that look like a spider web but have not deteriorated further since a CA bath.  The current lead problem is common knowledge you do business with the chinese and this is what you get.  The worst mistake this country ever made was selling, I mean giving,  china "Most Favored Nation" status.    I just happen to have a photo handy of a MTH smoke unit which I took out of a MTH 20-3029-1  SP Daylight loco that I bought new in 1999,by 2002 I had to replace it.  The bottom of the blower cage and the motor fell out.  I decided to see if I could save the thing and made a new bottom out of plastic and doused the rest of the casting in CA. Well, that was at least 16 years ago.  I pulled it out of a box of parts  a couple of months ago and it has not deteriorated to any noticeable extent since I washed it in CA. Though it is swollen a full 1/8" wider than original it seems solid and works fine.  So I put it in a Lionel 18000 B6 switcher when I added TMCC this summer.  As I said it's not a perfect solution but a solution none the less.           j

I have a MTH 20-3029-1 GS4. The locomotive itself was made in South Korea. So the only way the Chinese were at fault for the smoke unit zinc rot is if the smoke units at that time were made in China. 

To show how random the problem is the GS4 has been converted to PS2 and still has its original 20 year old smoke unit. Works great (I have changed the wick).

Lou your right I just dug out the GS4 box and sure enough it says made and litho in Korea.   I stand corrected.  However it was chinese food additives used in Walmart pet food which killed my cat.  And the smoke unit blower casting has been stable for 16 years after a bath in CA.                     j

Interesting statement on Wikipedia, don't know if it has any validity.

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.

gunrunnerjohn posted:

Interesting statement on Wikipedia, don't know if it has any validity.

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.

Perhaps it is the paint sealing the surface which delays or prevents it and not the acid bath. Assuming a complete wash neutralizing the acid.  We need a REAL metallurgist.  I remember either a chemistry or physics course having a chapter on it but that was over fifty years ago and I can't remember what I had for lunch yesterday.  Just as a mental exercise imagine batches of molten zinc having differing levels of lead contamination and cooking in the pot for different times.  The longer it cooks the more thoroughly the lead is blended into the zinc and the web pattern gets tighter and tighter till it disappears. The lead did not go away but broke down into small clumps of molecular pairs. Would that not explain differing patterns of rot on the surface. Some show the web pattern on the surface and some have a uniform cover of metallic salts.  The next question which comes to my mind, does the process start inside the casting or does it start on the surface and move inward. I think it starts on the surface where there is air and water and moves inside and the more moisture the faster it progresses. That explains why coating the casting with paint or in my case CA slows the process.    Gotta be one metallurgist in the group, how bout getting in on this.           j

You would think that after nearly a hundred years of dealing with this problem they would have solved it by now.

gg1man posted:

You would think that after nearly a hundred years of dealing with this problem they would have solved it by now.

The US factories figured it out a long time ago. Making the same types of toys for many years, they have to stand by the results of their work.

The Asian factories might take longer because they do not see the results of their work. As already mentioned, there are lots of mom and pop foundries that never see the results years later because they are either closed, or making something else. They never have to make reparations or honor guarantees.

To avoid a shark attack, stay out of the water.  (SURVIVOR TV series survival handbook.)

To avoid zinc pest, avoid zinc!

Dominic Mazoch posted:

To avoid a shark attack, stay out of the water.  (SURVIVOR TV series survival handbook.)

To avoid zinc pest, avoid zinc!

In other words don't buy Lionel,  MTH,  Williams,  Atlas , Weaver .........Trains ?    That doesn't work for me, bet I'm not alone.           j