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View Full Version : Why I don't like Zamac........



J Tiers
04-14-2008, 12:00 AM
Here is a prime example.......

It is (or WAS) a flywheel from an old Bogen AM/FM tuner that a friend of mine brought over for me to check out a problem on. He mentioned the AM was jammed, and when I looked at it this was the flywheel (for making the tuning action feel smoother and more "quality").

This is typical of bad zamac.... probably had some contamination, possibly lead. Cracks, splitting, growth, etc.

Of course it might be a slightly different zinc casting alloy, but the various zamac varieties are/were quite common, and it very probably is one of them.

I will happily admit that when made right, the alloy holds up as well as most metals, and within its strength limits. But there was enough bad alloy used (such as this example) to "poison" the reputation of the material.

Even extensive users such as Atlas Press got burned with bad batches, and they had quite an incentive to keep good QC...... since their products used a lot of it.

http://img.photobucket.com/albums/0803/jstanley/zamac.jpg

lazlo
04-14-2008, 12:17 AM
Zamak was intended as a low-cost substitute for grey cast iron. Zamak 7 has the same tensile strength as Class 40 cast iron, but doesn't have the vibration damping capabilities of grey cast iron.

With modern technologies and the cost of raw materials, especially the Zinc and Copper, it doesn't seem like a financially viable alternative these days.

It melts at low temperatures, so you can easily cast it in a home shop, but it's currently running $2.85 /lb, and Versa-Bar and Dura-Bar (continuously-cast grey or ductile iron) is running $1.80/lb.

J Tiers
04-14-2008, 12:40 AM
Oh, you wouldn't want to use it, probably.

But there have been some "it's perfectly good, why you doggin it?" responses in prior threads. I thought I would show an example of the bad kind so folks who didn't understand could see the nature of the problem I (and many others) have seen.

rantbot
04-14-2008, 02:22 AM
It looks like a piece of mystery metal afflicted by zinc pest. That is avoided by keeping the lead content down. Zamak made to specification does that. Mystery metal, of course, may not.

HTRN
04-14-2008, 04:33 AM
Yeah, that's zinc pest (http://en.wikipedia.org/wiki/Zinc_pest) allright.


HTRN

wirewrkr
04-14-2008, 07:36 AM
Well ya learn something new everyday. Zink Pest. that explains several oddly destroyed cast BMW motorcycle parts from the post war era that I have seen.
Sure does machine easy though. when it's not pesty anyhow.
R

boslab
04-14-2008, 08:44 AM
high residual dissolved oxygen, >1000ppm, same thing in steels [the old datsuns eat themselves away too]
mark

J Tiers
04-14-2008, 09:06 AM
The lead issue is a problem.......

"Mystery metal"? I imagine it was NOT supposed to be "mystery metal", but instead, a known zinc alloy, probably zamac. The fact that it ended up as mystery metal is no doubt cost-driven.

The use of lead apparently made the alloys flow and fill the mold better. Of course, lead is NOT part of the actual formula for zamac, but the temptation to throw in some lead to get production out without losing money must have been considerable.

With the generally more complex parts used in the Atlas products, I would suppose the temptation must have been severe. Thin sections, the need for complete filling for appearance and function, and strong pressure to keep costs down. All would have pushed the casting vendor to cut corners.

After all, the entire reason for using zamac was to cut costs.

Of course even a company that had standards and decent QC would not necessarily FIND the problem. It only appears after many years of use, long after any chance of tracing back and getting satisfaction from the casting vendor is long gone. Chemical analysis would probably not have been considered back then, since the problem was not suspected.

So the casting supervisor at some nameless subcontractor is the person who controls whether or not your Atlas lathe (or other item) is usable or just another worthless item to be "parted out".

The good news, I suppose, is that RoHS would rule out such shortcuts these days.

JCHannum
04-14-2008, 09:13 AM
It first should be pointed out that Zamak was a trademarked name for a family of zinc alloys that were made for specific applications. It is only one of a very large number of alloys that make up the materials usually referred to as "die cast". Simply because a part is made of die cast material, it does not follow that it is Zamak.

Yep, Zamak and other die cast parts do not last forever. Die cast was the material of choice in the early part of the last century as an economical substitute for cast iron, brass or machined steel parts. It was relatively inexpensive and accurate cast parts requiring little additional machining could be cast from it. It has been replaced by plastics in many of these applications.

While that failure is typical, it is not necessarily a fault of the material. It is the result of someone doing something wrong. A proper alloy, that has not had scrap or contaminants added, and is applied properly will give an acceptable service life. What is the age of that tuner?

J Tiers
04-14-2008, 09:25 AM
Simply because a part is made of die cast material, it does not follow that it is Zamak.


Quite true, a fact I pointed out.



What is the age of that tuner?

Early/mid 1960s. Old enough to be tube, recent enough to include FM stereo.

Rather new for such an advanced case of "rot".

A.K. Boomer
04-14-2008, 10:06 AM
Thanks for the warning, that stuff looks like overheated bakelite, What junk...

tony ennis
04-14-2008, 10:15 AM
So you pulled from a 40 year old radio a rotted tuner flywheel that may or may not be made of ZAMAC...

Therefore, Atlas lathes are bad.

lolz.

Optics Curmudgeon
04-14-2008, 10:21 AM
Wanna get fired from a die casting plant? Just bring in a lead hammer, goes over like a cockroach in an operating room. Also, die castings, especially those a little "off" in their formulation, can be very sensitive to the environment they are stored in. Then again, so are many other metals, like the table saw I stored in a friend's shed, which was also used to store a small quantity of pool chlorine. The saw (all cast iron) was barely salvageable a year later, it looked like it was stored in salt water.

Joe

JCHannum
04-14-2008, 10:57 AM
Rather new for such an advanced case of "rot".

Not necessarily. The material is probably not Zamac, and quite likely is substandard. If the radio had been stored in an unheated attic or a garage shelf for a year or two, it could have happened in a very short time. It would not be surprising to find that it has spent the last twenty years of it's life in some such of a storage area, not in daily use.

I would seriously doubt that every other component of the radio was in excellent, as new condition, and the only faulty part was the diecast tuner wheel.

macona
04-14-2008, 12:38 PM
In all reality I am sure the maker of the receiver never expected someone to still be using it 40 years down the road.

Murphy
04-14-2008, 04:32 PM
I've been a locksmith for over 25 years, and the locks in cars for years have their major parts made of a Zamak or similar alloy, and they last for years, with little or no maintainence.

Likewise, Sargent & Greenleaf have used Zamak for the bodies of their combination safe locks, again with excellent results,both in accuracy of part and long lifespan.

Zamak alloys have a odd quirk to them - they form a hard wearing surface on the outside that is much softer once the surface is broken, Try drilling the stuff, you've never seen a drill bit go dull so damn fast in your life!

All in all, it has its place in the scheme of things, like making cheap-ass .25ACP pistols, like the Raven pistol,or the Lorcan and Jennings pocket pistols!!!

Allen

J Tiers
04-14-2008, 11:05 PM
There is some interesting other information to go with the picture......

1) there was an IDENTICAL flywheel on the FM section of the same tuner. It is perfectly OK, with no particular problems. Certainly NO radical zinc pest issue....

2) the radio, for the doubters, works.


As far as the composition, of course it may not be a true zamac... in fact, its condition almost proves it isn't, since I have zamac parts on older machines (Some of them Atlas, Mr very insulted Ennis), which were stored/kept in worse conditions, and are ok. (and some that were unusably bad, though none THAT bad)

But, it is a zinc casting alloy, of a similar general composition to zamac. The good condition of the second flywheel (and a number of zamac items on my Atlas stuff) shows that GOOD material OF THE SAME TYPE won't rot away.

Naturally, since the two were 8 inches apart for the last 40+ years, they had identical environmental conditions. One "rotted", one didn't. Go figure.

Now that I think about it, there were zamac split collets on my Atlas 18" industrial drill press. All were swelled, cracked, etc. So was the depth control slider. But two OTHER zamac parts on the drillpress were OK.

I WISH the split cotters had been that bad, they were still solid, and had to be driven out of their holes with a heavy hammer and lots of PBlaster. They were almost 1 1/2 inches diameter. If they had been all split, they might have been easier.




So you pulled from a 40 year old radio a rotted tuner flywheel that may or may not be made of ZAMAC...
Therefore, Atlas lathes are bad.
lolz.

How very odd that you would draw that out of my post. I didn't say that.

If you want to be insulted, be my guest. But it IS a bit tiresome, so do it in silence, if you please. :rolleyes:

wierdscience
04-15-2008, 12:54 AM
J,that is bad,I was tld once by a man who worked for Carter carburators that even if the correct alloy of Zamak was used it could be ruined by overheating before the pour.A malfunctioning thermo-couple or an in-experienced operator was all it took according to him.

wierdscience
04-15-2008, 12:59 AM
Well ya learn something new everyday. Zink Pest. that explains several oddly destroyed cast BMW motorcycle parts from the post war era that I have seen.
Sure does machine easy though. when it's not pesty anyhow.
R

BMW?Are you sure that was zamak? BMW is famous for using magnesium which rots when soaked or immersed in fresh water.There was a write up on a fellow who restored BMW aircraft engines from WWII.He said it took him four engines worth of castings to get enough sound parts to make one working engine because of the disappearing nature of mag in rain water.

Come to think of it VW used lots of mag,stands to reason since Germans are facinated with things that burn and blow up:D

IOWOLF
04-15-2008, 07:16 AM
So you pulled from a 40 year old radio a rotted tuner flywheel that may or may not be made of ZAMAC...

Therefore, Atlas lathes are bad.

lolz.


Sounds like it, But I can't believe that is what he means.

JCHannum
04-15-2008, 09:03 AM
There is some interesting other information to go with the picture......

1) there was an IDENTICAL flywheel on the FM section of the same tuner. It is perfectly OK, with no particular problems. Certainly NO radical zinc pest issue....

2) the radio, for the doubters, works.


As far as the composition, of course it may not be a true zamac... in fact, its condition almost proves it isn't, since I have zamac parts on older machines (Some of them Atlas, Mr very insulted Ennis), which were stored/kept in worse conditions, and are ok. (and some that were unusably bad, though none THAT bad)

But, it is a zinc casting alloy, of a similar general composition to zamac. The good condition of the second flywheel (and a number of zamac items on my Atlas stuff) shows that GOOD material OF THE SAME TYPE won't rot away.

Naturally, since the two were 8 inches apart for the last 40+ years, they had identical environmental conditions. One "rotted", one didn't. Go figure.


I guess I don't understand the point of your post. I seem to gather that the reason you hate Zamac appears to be because parts that might not be made of Zamac deteriorate when stored in a humid environment while parts that might be made of Zamac don't.

Zinc alloys used for diecasting can have many different compositions, and collectively are often referred to as "pot metal". Pot metal can be considered the mystery metal of these alloys. Some of these alloys do not hold up well for whatever reason, while others last for years. The auto industry has used diecast alloys for years with success, and continues to with many components.

For some reason many people think all pot metals are Zamac. That is not the case any more than all steels are Bethelem. It is no more possible to identify a part as being made of Zamac by looking at it than it is possible to identify the manufacturer or a particular steel alloy by looking at it.

I have no doubt that the radio works, I simply question whether the single component that has failed over the forty some years of it's existence is the pot metal flywheel.

Does Zamac fail under adverse conditions or misapplication? It most certainly does, but name one material that does not.

J Tiers
04-15-2008, 09:25 AM
THE POINT IS NOT THAT ANY BRAND OF MACHINE IS BAD.

THE POINT IS NOT THAT "MISAPPLICATION" (NOT APPLICABLE HERE) IS WHATEVER YOU SAID IT WAS OR WAS NOT.

The point is simply that I have been severely slammed for saying that various zinc casting alloys, generally termed "zamac" (correctly or incorrectly) were not a good choice of material because they have a history of "going bad".

Here we have two pieces of presumably identical material, stored in what the most fussy and fanatical proponent of "zamac" cannot deny were identical conditions.

Neither part is even stressed in its usage, it simply has to be one piece, and stay in place. Hardly a tough application. The point of the radio working is (obviously) that it was not dug out of the mud, etc, it was stored in a house, without roof leaks etc.

ONE "went bad" and the other did not.

Quite obviously the conditions of assembly and storage (in same unit, inches apart) totally eliminate the "adverse environment" argument.

And they tend to preclude the "well it was a bad batch" argument, unless two parts that clearly came out of the same bin at the same time were from wildly different batches, one very bad, one fine.

Anyone who actually read the thread would have noticed the point much earlier......


But there have been some "it's perfectly good, why you doggin it?" responses in prior threads. I thought I would show an example of the bad kind so folks who didn't understand could see the nature of the problem I (and many others) have seen.

Done deal, JC..... THAT PICTURE is typical of the sort of failure you have obviously never seen, and consequently do not understand. Known zamac has had very similar failure, regardless of what this particular part was or was not composed of.

Now that you HAVE seen it, you will from now on understand why those of us who have had the problem do not particularly like the material..... It has the very strong potential to turn an otherwise usable piece of machinery into useless scrap, when an essential and complicated cast part fails.

rantbot
04-15-2008, 09:48 AM
I still don't see how the failure of a part which almost certainly isn't made of Zamak (which we can reasonably conjecture from the failure mode itself, which isn't typical of any of the real honest-to-gosh Zamak alloys) tells us anything about failure of parts which are made of Zamak.

John Stevenson
04-15-2008, 09:56 AM
Oh sht here we go YET again.

Fetch my violin............................


.

A.K. Boomer
04-15-2008, 10:03 AM
JT and JC, come on now -- its almost summer out there --- git along now er im fixin to git sideways on someone (the fightin kinda sideways):eek:

It is kinda strange around here -- its like were still in the dead of winter sometimes, take pill if you have to - yeah, imagine that - me telling someone else to chill out:rolleyes:


Signed; Roy D. Mercer

Bill Pace
04-15-2008, 10:18 AM
Another unfortunate example of a guy starting an interesting thread sharing an experience, and his thoughts on it ... only to get belittled, berated, tarred and feathered, boiled in oil ----GEEEZ! its no wonder this site is suffering from interesting content ..who in their right mind wants to put up with these kind of responses......

JCHannum
04-15-2008, 10:55 AM
No prolonging of a discussion, I have never denied that diecast will fail as pictured and I am quite familiar with it. I have also seen just about any other material you can name fail at one time or another. It is a simple fact of life.

Tinkerer
04-15-2008, 12:40 PM
Here we have two pieces of presumably identical material, stored in what the most fussy and fanatical proponent of "zamac" cannot deny were identical conditions.

Neither part is even stressed in its usage, it simply has to be one piece, and stay in place. Hardly a tough application. The point of the radio working is (obviously) that it was not dug out of the mud, etc, it was stored in a house, without roof leaks etc.

ONE "went bad" and the other did not.

Quite obviously the conditions of assembly and storage (in same unit, inches apart) totally eliminate the "adverse environment" argument.

And they tend to preclude the "well it was a bad batch" argument, unless two parts that clearly came out of the same bin at the same time were from wildly different batches, one very bad, one fine.


What was the wheels proximity to the tubes in the radio? Some types have a greater radiant heating effect than others. I've seen similar effects on plastic wheels and gears that were to close to a heat source dried out and deteriorated. So if one heated up more so then the other moister/humidity could of had a greater effect on it over the many years. Or it could of been the daily heating and cooling cycle that did it.


Just because some tires go flat... does not mean all tires will go flat... and to condemn all tires based on a few bad tires really hold no air. :)

TGTool
04-15-2008, 01:15 PM
To me, the most useful information is how variable some parts can be in aging. Assuming (yes, I know...) that both parts were supplied by the same manufacturer to the radio builder, we learn that quality control in casting those parts wasn't very good. And we see a good example of very extreme deterioration.

The unfortunate part is including Zamac in the title of thread since one or another or both of these parts may not be Zamac. That simply hasn't been established. And generalizing from here to too broad a class doesn't seem warranted. Just because some diecast parts, which we believe to be Zamac with a high degree of confidence, don't degrade is no guarantee that some other part in some other machine won't.

The most we can say with confidence based on this evidence is that with age some pieces can turn to crap. Interesting example but no surprise.

aboard_epsilon
04-15-2008, 01:16 PM
Here is a prime example.......

It is (or WAS) a flywheel from an old Bogen AM/FM tuner that a friend of mine brought over for me to check out a problem on. He mentioned the AM was jammed, and when I looked at it this was the flywheel (for making the tuning action feel smoother and more "quality").

This is typical of bad zamac.... probably had some contamination, possibly lead. Cracks, splitting, growth, etc.

Of course it might be a slightly different zinc casting alloy, but the various zamac varieties are/were quite common, and it very probably is one of them.

I will happily admit that when made right, the alloy holds up as well as most metals, and within its strength limits. But there was enough bad alloy used (such as this example) to "poison" the reputation of the material.

Even extensive users such as Atlas Press got burned with bad batches, and they had quite an incentive to keep good QC...... since their products used a lot of it.

http://img.photobucket.com/albums/0803/jstanley/zamac.jpg

you know what ...
that part reminds me of something that has dried out ...not corroded ..

maybe ...it had something in it that evaporated over time .

J Tiers
04-15-2008, 09:18 PM
you know what ...
that part reminds me of something that has dried out ...not corroded ..

maybe ...it had something in it that evaporated over time .

That seems very doubtful..... I mean, it IS "metal". And one just like it did not do it.

As far as the proximity to tubes........... it was in storage, not in use.

And I already mentioned that this piece may not be "zamac", BUT IT DOESN"T MATTER....

Despite the fact that a few folks decided to get off the train a few stops too early........................ and missed the point.......

This IS THE SAME TYPE DETERIORATION that cast parts (which we do not know were zamac either) from various manufacturers have had.........

So whether it is "really zamac" isn't the point, it is an example (extreme, of course) of what can and DOES happen...............

bhjones
04-16-2008, 08:39 PM
Then why did you use Zamak in the title of this thread. It should have been "why I don't like unknown zinc based alloys".

These last two lines are a great example of double speak. Between the title and the closing line that this "Does" happen (I presume you mean to Zamak since it's the title to this thread), your claims that people are missing the point rings hollow.



This IS THE SAME TYPE DETERIORATION that cast parts (which we do not know were zamac either) from various manufacturers have had.........

So whether it is "really zamac" isn't the point, it is an example (extreme, of course) of what can and DOES happen...............

J Tiers
04-16-2008, 11:59 PM
Then why did you use Zamak in the title of this thread. It should have been "why I don't like unknown zinc based alloys".

These last two lines are a great example of double speak. Between the title and the closing line that this "Does" happen (I presume you mean to Zamak since it's the title to this thread), your claims that people are missing the point rings hollow.

:D :rolleyes:

lazlo
04-17-2008, 12:20 AM
He's got a very good point Jerry :)

J Tiers
04-17-2008, 01:28 AM
No, actually the "point" you refer to does NOT exist. It appears to be simply trolling activity...... since the issues were previously dealt with, I don't know why I bother to even reply and explain yet again....... but........ (sigh).......

Atlas are generally considered to have used "zamac".

Of the 15+ pieces of cast zinc material I have had to replace in machines due to deterioration of a type similar to that (extreme) case in the picture, 12 have been from Atlas.

Accordingly, we can presume they were "really zamac".

The others (non-atlas) may well have been as well. They had a similar problem, looked the same, etc.

There are a lot of types of zamac, and at one time or another apparently 70% of the zinc castings made in the US were some form of zamac. More like 90% if you include closely allied (but not that actual brand) alloys. That info is from one of the references I found, probably through a wikipedia footnote.

The statement the apparently spiteful poster gleefully points to as "irretrievably damning" was an ironic comment based on the fact that I don't of my own knowledge know that Atlas truly used zamac. And it is pretty irrelevant anyway. The poster is pretending to be dense, but we know he is not.

While it is widely accepted, and the TERM "zamac" is in common usage for the Atlas material, I could not "swear in court" that it is zamac. Can you?

We know what is meant without needing nitpicking, pettifogging quibbles.

It is a case of debating the details by people who can't argue the real point, and so refuse to see the picture as simply an example (an extreme example, of course) of the exact same problem that I have seen on the "zamac" castings from a number of brands of equipment, including, but not exclusively, on Atlas. Not all of them are even metalworking machinery.

I thought it would be instructive to show what the problem looks like, because there is a certain amount of "zinc pest denial". There has been considerable comment along the lines that there is no such problem, apparently because the persons denying the issue have never seen it.

It's been fun, and it's been real, but it hasn't been real fun.

Whatever.

lazlo
04-17-2008, 02:24 AM
Jerry, I'm not picking on you, but if you read through the replies, I don't think most of us understand the point of your post.


Why I don't like Zamac

This is typical of bad zamac.... probably had some contamination, possibly lead. Cracks, splitting, growth, etc.

Then you go on to say that the the tuner flywheel is probably not Zamak.

Atlas used authentic Zamak (spelled with a 'K') -- a registered trade mark of the New Jersey Zinc Company. It was licensed from a Germany company which invented the alloy -- ZAMAK is an acronym for Zinc, Aluminum, MAgnesium, and Kupfer (German for copper).

http://www.lathes.co.uk/atlas/

So how is the Zamak in your Atlas lathe related to the tuner flywheel? :confused:

rantbot
04-17-2008, 03:37 AM
Of the 15+ pieces of cast zinc material I have had to replace in machines due to deterioration of a type similar to that (extreme) case in the picture, 12 have been from Atlas.
If the picture accompanying the original post had been one of those decayed Atlas parts, this might have been an informative thread. But it wasn't, it was a photo of some miscellaneous junk. That tells us nothing at all about the behavior of properly engineered alloys.

A.K. Boomer
04-17-2008, 08:20 AM
Sweet muther of christ here we go again, I actually think Aboard _epsilon is right on the money with his reply of;


"you know what ...
that part reminds me of something that has dried out ...not corroded ..

maybe ...it had something in it that evaporated over time ."



That's a much better description of the part than corrosion --- corrosion does not single out those kind of paths unless the part was not "mixed" properly and then it will not even remotely resemble that pattern --- you can see great fissures form the same kind of patterns in dry lake beds and such, I think the part shrunk --- while at the same time losing its elasticity --- this directly equates to it moving in smaller "blocks"...:cool:

JCHannum
04-17-2008, 08:49 AM
It is definitely some form of corrosion. It may be intergranular corrosion or a close relative. Intergranular corrosion occurs with stainless steel and other alloys including aluminum and titanium under certain circumstances. The appearance and result is somewhat similar. The material virtually crumbles into dust.

http://www.corrosion-club.com/intergr.htm

oldtiffie
04-17-2008, 09:11 AM
As a slight diversion, from post-war to some time after, just about every "shiny aluminium-looking" die-cast item was known as "Sh*t metal" - and quite often for very good reasons. It was weak, had "mold-flashes" and surface cracking everywhere, lost its shine readily and melted easily.

Local legend had it that it came from post-war Japan. Probably so tho' I'd guess that some of the "locals" either trying to get (re)established might have been offenders too.

Same sort of (lack of) "quality" issues applied to many cheap (Asia/Japan) pressed-metal toys etc.

J Tiers
04-17-2008, 09:32 AM
If the picture accompanying the original post had been one of those decayed Atlas parts, this might have been an informative thread. But it wasn't, it was a photo of some miscellaneous junk. That tells us nothing at all about the behavior of properly engineered alloys.

Laslo, you are hereby awarded the prize for the day. it is not an honor.

You have just stated, but COMPLETELY MISSED, the point.

THE PROBLEM IS NOT WITH PROPER ALLOYS. I said this, but you missed it.

THE FREAKING PROBLEM IS THAT THERE ARE SO MANY PARTS THET WERE SUPPOSED TO BE MADE WITH THE RIGHT STUFF, BUT THEY WERE MESSED UP, AND SO THEY FAIL JUST LIKE THAT

I said that but you missed that too.

They LOOK just like "good" parts, but they ARE GONNA FAIL.

I DON'T LIKE THE STUFF BECAUSE A BAD PART LOOKS THE SAME AS A GOOD ONE UNTIL IT CRUMBLES.

WHEN IT DOES CRUMBLE, IT LOOKS LIKE THE BAD PART IN THE PICTURE.

YES, THAT IS CORROSION. IF YOU DON'T LIKE THAT, TOO BAD. LOOK UP ZINC PEST.

FACTS TAKE NO ACCOUNT OF YOUR PERSONAL LIKES OR DISLIKES. Sorry to burst your pretty bubble.

A.K. Boomer
04-17-2008, 09:58 AM
[QUOTE=JCHannum]It is definitely some form of corrosion. It may be intergranular corrosion or a close relative. Intergranular corrosion occurs with stainless steel and other alloys including aluminum and titanium under certain circumstances. The appearance and result is somewhat similar. The material virtually crumbles into dust.





Ill see your corrosion club and raise you a corrosion doctors; www.corrosion-doctors.org/Forms-intergranular/intergranular.htm - 10k -

Although that pic is an example of 7075 aluminum it is a great example of intergranular corrosion --- Im not saying there is none of this occurring in JT's pic but there is another factor going on there, too much gaps while other pieces are holding together --- almost like the piece was under a tension battle over the years, perhaps the corrosion etched a path and then it just went crazy because the piece would open up more and more for it, also if you look at the massive fissure from the center hub it looks like the outer beef on the inner hub is oval --- this is not from corrosion, this is from the part being relieved of tension from the crack and actually changing its shape...
its no secret that parts that are under internal tensions yet have been cast into a pre-determined shape can develop issues with BOTH corrosion AND shrinkage and or growth, telling them apart actually takes some study, many times the study will amount to both being a factor or without one the other would not exist...

JCHannum
04-17-2008, 10:40 AM
Boomer, I merely said it is possibly something similar to intergranular corrosion. Both I/G corrosion and the failure of diecast parts can have very different appearances with different alloys and conditions. With diecast, it seems to when the part is exposed to damp conditions.

Why is JT abusing Laslo for a quote by rantbot? Is because it is a quote like Laslo would make if he had made it? Honestly, it all gets so confusing.

rantbot
04-17-2008, 11:33 AM
I DON'T LIKE THE STUFF BECAUSE A BAD PART LOOKS THE SAME AS A GOOD ONE UNTIL IT CRUMBLES.
This is true of most materials. So what metals do you like?

You're still mired in your basic misidentification problem. By "the stuff," do you mean Zamak, as identified in the title of the thread, or do you mean the crap alloy in your picture? They're not the same thing.

lazlo
04-17-2008, 12:04 PM
Why is JT abusing Laslo for a quote by rantbot? Is because it is a quote like Laslo would make if he had made it? Honestly, it all gets so confusing.

I'm pretty sure JT meant to say "Rantbot" in his rant. :confused: Either that, or he meant to put my quote with that post. I think my post was pretty civil -- oh well :)


You're still mired in your basic misidentification problem. By "the stuff," do you mean Zamak, as identified in the title of the thread, or do you mean the crap alloy in your picture? They're not the same thing.

I think Jerry's point is: "Zinc alloys suck. Zamak is a zinc alloy, therefore Zamak sucks."

My corollary is: "Steel rusts. 304 Stainless is steel, therefore 304 rusts."

A.K. Boomer
04-17-2008, 12:08 PM
Why is JT abusing Laslo for a quote by rantbot? Is because it is a quote like Laslo would make if he had made it? Honestly, it all gets so confusing.


I think he got upset because like you stated it might be a quote like Laslo would make, and JT's no dummy, he knew that ahead of time, but because Laslo didnt make it thats actually what upset him, If Laslo made the quote then he would have had proof positive and he would have got upset but not as much as this because he knew Laslo wanted to and didnt -- in which case logic follows that if Laslo did make the comment Rantbot would have taken the beating for it ---- so he kinda thinks Laslo took the easy way out, but he didnt because he got beat on even worse for not making the comment, for me its incentive that we all keep talking about things we dont have a clue about --- were still going to get beat on, but at least we got to have a say before it happened and in doing so the beating should be a little less also...

lazlo
04-17-2008, 12:14 PM
A.K., have you tried to read your post? You have a 6-line paragraph without a single period. :)


it might be a quote like Laslo would make,

So... what's a quote like Lazlo would make? :rolleyes:

A.K. Boomer
04-17-2008, 12:26 PM
So... what's a quote like Lazlo would make? :rolleyes:









"A.K., have you tried to read your post? You have a 6-line paragraph without a single period. :)"


;>}

Please change all my S's to Z's on your name, I was copying someone else and repeated there mistake over and over...

lynnl
04-17-2008, 12:32 PM
I think some people got up on the wrong side of the lathe bed this morning. :D

JCHannum
04-17-2008, 09:02 PM
Sorry about the s's, I missed the z's too.

John Stevenson
04-17-2008, 09:05 PM
OK come on and fess up, it's an old bathplug isn't it ?

http://img.photobucket.com/albums/0803/jstanley/zamac.jpg



.

aboard_epsilon
04-17-2008, 09:09 PM
OK come on and fess up, it's an old bathplug isn't it ?

http://img.photobucket.com/albums/0803/jstanley/zamac.jpg



.

yeah had a few bath plugs that went like that ...
think the stuffs called mazak in the uk

all the best.markj

bsmith
04-17-2008, 10:02 PM
I think I am the kind of person JTiers was hoping to help with this thread. I have heard for some time about the various problems zinc alloys and pot metals can have, but I never had a good idea of just how severe they could be. The picture JTiers posted was quite enlightening although it is an extreme example.

I am also amazed at how many people want to defend these cheap alloys. The point I am taking from this thread is that I want to avoid owning any machine that uses a significant amount of zinc alloy parts.

I think the anecdotal evidence is very strong that a machine using zinc alloy parts has a higher likelihood of early part failure than a similar machine that uses cast iron or steel for the same parts. I really don't see how anyone can argue that point.

JTiers, thank you for creating this thread. As I acquire more machinery I am going to do my best to avoid zinc alloys and pot metals and this includes even a machine that claims to have perfect composition Zamak in it.

lazlo
04-17-2008, 10:12 PM
A couple of counter-examples of zinc alloy that are successful: the step pulleys and belt guards on a lot of machines, including the Bridgeport E-Head (Shaper head) are some kind of zinc alloy. I know this because I bought an E-Head that was dumped off a fork-lift, and I got to see, and attempt to repair, the inside of the pulley stack and the belt guard :) The end-bells on many (quality) three-phase induction motors are zinc alloy. American pennies made since 1982 are 97.5 percent zinc and 2.5 percent copper. Many (most?) household faucets and shower fixtures are zinc alloy (presumably Zamak 3).

And as "Murphy" the locksmith pointed out, zinc alloys are used a lot in the locksmithing industry. There's a How Its Made episode about the American company that makes the card reader locks for hotel doors. The entire chassis is zinc alloy.

Like several folks have already said, there are many different zinc alloys, including pot metal, and the Zamak family are very specific zinc/magnesium/aluminum/copper alloys. So it's tricky to extend generalizations about mystery alloys and pot metal to specialty alloys like Zamak.

Edit: according to Wikipedia (I had to wait for Tiffie to get done using it ;) ), most of the zinc die casting in North American is made with Zamak 3 (Zinc + Aluminum), so there's a good chance that the hotel door locks are Zamak-3:

ZAMAK 3

ZAMAK 3 is the de facto standard for the ZAMAK series of zinc alloys; all other zinc alloys are compared to this. ZAMAK 3 has the base composition for the ZAMAK alloys (96% zinc, 4% aluminum). It has excellent castablity and long term dimensional stability. More than 70% of all North American zinc die castings are made from ZAMAK 3.

J Tiers
04-17-2008, 10:53 PM
I dunno WHO to quote, the quotes are quoted and re-quoted.

Whatever.

If you WOULD please read the post before spouting........ I at least TRY to understand the sometimes tangled sequence of quotes........ and quotes that are not quoted the standard way


if anyone had said this, it would be a quote when shown like this

but this wouldn't look like a quote, even if it were one

anyway...

For the 4th (?) time, in simple words (yet again)... Considerable amounts of what was presumably SUPPOSED to be zamac (which lasts VERY well, actually) was apparently polluted, which I suppose makes it technically NOT zamac, whatever the print called for. The polluted stuff, which may have had only a little too much lead, corrodes, sometimes horribly, sometimes just enough to be brittle.

The pollution could have been accidental, a bad analysis, etc.

OR it could have been a deliberate act by a foreman who wanted the easier molding that a bit of lead is said to provide, and who did not give a hootski how long the part lasted.

So ranty-bot, that is the point...... Real, unpolluted "zamac" isn't identifiable by visual appearance, or smell.

If a machine uses it, you have NO CLUE by looking at it as to whether it is bad stuff that will start to corrode after it is moved into your particular environment, and fall apart, or if it is good stuff that will work as well as it can.

You can't tell if the seeds of corruption are in there, or not. So it is something of a crapshoot. It might be in an environment that prevents corrosion, like up in the frozen North at low humidity. You change that environment, and you may get mush......

Since it was usually used for intricate parts that are a pain to make in any other way, you will feel the pain if you lose your gamble. The worst part is that you may have to re-engineer the part, and mating parts, if there is substantial distortion of the part when you discover the problem.

The exception seems to be if you live down South. Any zamac that survives in Missouri and points South is probably good stuff, and you may be pretty safe with it. if it was gonna go bad, it probably already would have.


As for the doubters, who say there is some funny biz with the picture.

First, thanks for thinking I am a liar. I appreciate it, you don't know how much. :rolleyes:

Second, this part was simply pressed onto a knurled part of a shaft. That probably started some stress corrosion, but there was no other force etc on it. It just got typical humid Missouri storage.

The egging out seems to be the result of simple gravity acting on the part. There wasn't any other force acting, once the part cracked and relieved the forces due to pressing on.

I have actually tried to break it, assuming that it would likely crumble. As bad as it is, and as much as it fails to work in its application, that part is still reasonably strong.

No force that I was comfortable applying by hand (visualizing zinc splinters sticking in me) will break it....

Another added point that I had forgotten......

The part was jammed hard between some other parts...... It had clearance before it cracked and expanded. The corrosion ACTUALLY FORCED IT APART, SO THAT IT WEDGED INTO A PLACE THAT IT USED TO HAVE CLEARANCE IN.

That is the most interesting part. The corrosion exerts force as it proceeds, expanding the part........ That explains the odd sort of cracking that you see in the pic.

oldtiffie
04-17-2008, 11:06 PM
Thanks JT for a good and cautionary "heads up" and discussion as regards potential problems with some zinc-alloy die-cast parts.

I'd have never thought to see if it was marked "Zamak" (sp?) or what-ever.

So far as I am aware, there is no "spark test" or "rule of thumb" to determine what the material is (or is not).

All too often those "die-cast" "bits" are very hard to duplicate and all but impossible to weld or repair if they fail.

Thanks for the good "pointer".

bob_s
04-18-2008, 01:43 AM
I the early 1970's General Dynamics investigated the loss of two F111a swing wing fighter jets.

The cause, the failure at low stresses of the 4340 wrist pins.

Tests on a large sample of the high strength alloy pins showed that failure on a small number of the pins could occur at stresses of less than 10,000 psi, about the equivalent of mild steel!

JCHannum
04-18-2008, 07:38 AM
[QUOTE=bsmith]I am also amazed at how many people want to defend these cheap alloys. The point I am taking from this thread is that I want to avoid owning any machine that uses a significant amount of zinc alloy parts./QUOTE]

If that is a concern, you will have to strike just about any automobile made off your list of purchases. While it is being replaced by "engineering plastics" in many areas, it is still widely used in the auto industry and many other applications.

When the "engineering plastics" fail they become reclassified to "cheap plastic sh*t".

Forrest Addy
04-18-2008, 01:21 PM
All I can contribute is my usual blather:

Bad metallurgy can bite any material. I have a 1960's Pow'r-Kraft (yup, says so right on the label) jointer made of cast iron. Over time it turns into a pretzel. The material isn't stable: the infeed and outfeed tables warp concave - bum metallurgy. Every few years I have to prep it and haul it to Seattle to get the table ground and it's been that way for 40 years. I would have replaced it long ago but it was my dad's.

I remember some cast bronze bow door bolts made for an LST given to the Vietnamese Navy. The raw castings laying on a pallet had cracked over the week end in a giraffe pattern. Too much zinc in the alloy.

A friend of mine cooked up a batch of mystery aluminum and cast a binnicle for his boat. He dropped it on DIRT and it shattered.

I've seen die cast alloy parts in stuff 70 years old performing as well today as it did in the '30's. There's nothing wrong with die cast parts if they are designed well and the material selected is suitable for the application. It has a number of virtues and a few vices but that could be said of any material. So it's brittle. It's also stiff, corrosion resistant, stable, pressure tight, die casts reliably to highly accurate very complex shapes, and low in per part cost in volume production. That's a good trade-off in most situations. But the metallurgy has to be right.

Broadcast condemnation of diecast zinc aluminum alloy is silly but I've done it myself when confronted with a cracked part and there's no way to repair it. It can't be welded, soldered, brazed, or nothing if a reliable repair is to be effected.

Foundries and metal alloy suppliers maintain large Q/A staffs headed by metallurgists for a good reason: uncontrolled matallurgy poses as many traps and hazards in its way to the end user as the worst tropical swamp full of crocodiles, piranhas, snakes, hungry cats, bugs, and disease to under-equipped explorers.

lazlo
04-18-2008, 03:18 PM
Great post Forrest -- definitely not blather in my book!

J Tiers
04-18-2008, 08:01 PM
Foundries and metal alloy suppliers maintain large Q/A staffs headed by metallurgists for a good reason: uncontrolled matallurgy poses as many traps and hazards in its way to the end user as the worst tropical swamp full of crocodiles, piranhas, snakes, hungry cats, bugs, and disease to under-equipped explorers.

Yep, they do NOW.........

But our issue originated 50 years ago, when it all looked like an unbeatable good deal.

Some is perfect. Some is so-so. And some is rotten.

Can you tell which is which. which will be fine and which will go bad, BEFORE IT DOES, by looking at it?

John Stevenson
04-18-2008, 08:21 PM
I still think it's an old rubber bath plug :D

.

oldtiffie
04-18-2008, 10:08 PM
I still think it's an old rubber bath plug :D

.

Probably right John.

I thought it was a fly button from the pants of some old "dribble dick". No wonder it was "corroded" and "eaten out".

(For this purpose, any kid will tell you that enyone (else) over 30 is "old" and almost by definition a "dribble dick").

After living in boarding-houses, single-mens quarters and the Navy (none had a bath - only showers) there is NO WAY that I'd bend over to look at or for or pick up the bath-plug - or the soap!!!.