Kegan
Member
Thank you for the discussion. Very informative
CASTING PARTS FROM TIN OR ZINC?
- Thread starter Kegan
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Followed up on the reference to "zink pest" in you post. Interesting. I saw plenty of examples in automotive parts like door handles and mount brackets in the '40s and '50s in my dad's garage. That's apparently where zink die castings got their bad name.
The pot metal stuff gave zamak a bad name.
All of the old toys made from it that I got from my dad crumbled.
New stuff is suppose to be better.
The Zamak 27 is very strong stuff.
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All of the old toys made from it that I got from my dad crumbled.
New stuff is suppose to be better.
The Zamak 27 is very strong stuff.
.
Just to be
Here is a page from one of the links I posted previously.
It seems like at some point they transition from calling it "Zamak" to calling it a "zinc aluminum alloy".
I think the melting point goes up as the number goes up, and the strength of the material also goes up with the number.
Call it what you will; I generally group them in the same category just like Dynacast does, because they are so similar.
When they get above 7, they start uing the "ZA" designation.
From Wikipedia:
(I think the second sentence explains the difference between the Zamak and ZA designations)
ZAMAK (or Zamac, formerly trademarked as MAZAK[1]) is a family of alloys with a base metal of zinc and alloying elements of aluminium, magnesium, and copper.
Zamak alloys are part of the zinc aluminium alloy family; they are distinguished from the other ZA alloys because of their constant 4% aluminium composition.[2]
The name zamak is an acronym of the German names for the metals of which the alloys are composed: Zink (zinc), Aluminium, Magnesium and Kupfer (copper).[2] The New Jersey Zinc Company developed zamak alloys in 1929.
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It seems like at some point they transition from calling it "Zamak" to calling it a "zinc aluminum alloy".
I think the melting point goes up as the number goes up, and the strength of the material also goes up with the number.
Call it what you will; I generally group them in the same category just like Dynacast does, because they are so similar.
When they get above 7, they start uing the "ZA" designation.
From Wikipedia:
(I think the second sentence explains the difference between the Zamak and ZA designations)
ZAMAK (or Zamac, formerly trademarked as MAZAK[1]) is a family of alloys with a base metal of zinc and alloying elements of aluminium, magnesium, and copper.
Zamak alloys are part of the zinc aluminium alloy family; they are distinguished from the other ZA alloys because of their constant 4% aluminium composition.[2]
The name zamak is an acronym of the German names for the metals of which the alloys are composed: Zink (zinc), Aluminium, Magnesium and Kupfer (copper).[2] The New Jersey Zinc Company developed zamak alloys in 1929.
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I failed to put a smiley face on my post - I was intending it to be humorous (as indicated by the strike-outs) - I hope it came across that way!
Its all good for me.
I am just here for the fun of it, and for the learning that can be had.
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Likewise!
If I recall correctly Dinky Car Toys were made from the same or very similar material.
Not to hang a left turn here but is there anyway to stabilize a part once the sink rot starts? Bob
I think Zinc-rot is generally a sacrificial loss of Zinc to Zinc Oxide due to moisture conducting an electrical path - e.g. across the surface of some paint - between a pin-hole in the paint and the steel (or other metal) the other side of the painted surface. The white stuff (Zinc "Rust") is Zinc oxide, as used medially as a sterilising chemical.
Think of an electrical circuit: Steel bits of Myford machine exposed to air, and about to oxidise... bolted to a block containing mostly Zinc, but painted except for a pin hole or 3.
DRY - there is no circuit for the zinc to electrolytically corrode, so the steel rusts, but when covered in a fine wet surface of condensation, the "return path" to develop a current for the electro-potential between the steel and zinc will causes the zinc to corrode sacrificially instead of the steel rusting. I.E. the lathe is a Zinc-Iron battery, discharging when the Cold lathe meets warmer moist air....
Zinc blocks are used on ships to prevent the bronze propellers and steel hulls from corroding, as the sacrificial zinc blocks corrode first due to the electro-potential therein.
I keep my machines blanketed, so the temperature differences have trapped air insulation around them and this mostly prevents the nasty corrosive condensation from attacking the steel - and any zinc.
(QED? (Latin for Quote-me-not?).
K2
Think of an electrical circuit: Steel bits of Myford machine exposed to air, and about to oxidise... bolted to a block containing mostly Zinc, but painted except for a pin hole or 3.
DRY - there is no circuit for the zinc to electrolytically corrode, so the steel rusts, but when covered in a fine wet surface of condensation, the "return path" to develop a current for the electro-potential between the steel and zinc will causes the zinc to corrode sacrificially instead of the steel rusting. I.E. the lathe is a Zinc-Iron battery, discharging when the Cold lathe meets warmer moist air....
Zinc blocks are used on ships to prevent the bronze propellers and steel hulls from corroding, as the sacrificial zinc blocks corrode first due to the electro-potential therein.
I keep my machines blanketed, so the temperature differences have trapped air insulation around them and this mostly prevents the nasty corrosive condensation from attacking the steel - and any zinc.
(QED? (Latin for Quote-me-not?).
K2
All metals oxidize and what do you do is to coat them with oil. The parts of a lathe or mill should be coated that are steel or cast iron I coat since they sit in my garage.
I think the problem is more than just electrolytic corrosion. This article about "zinc pest" from Wikipedia discusses it.
https://en.wikipedia.org/wiki/Zinc_pest
https://en.wikipedia.org/wiki/Zinc_pest
Good article Don. I was looking at Caswells catalog and they sell a plating material for pot metal/zinc. Presumably it will seal the part and maybe add a little to the appearance.
Thanks, Good information: Zinc Pest is a problem with OLD castings, due to impurities of lead... in localised concentrations.
"Zinc pest is not related to tin pest, and is also different from a superficial white corrosion oxidation process ("Weissrost") that affects some zinc articles".
I was only aware of the "white rusting" and corrosion blisters and pitting of (e.g.) chromed zinc alloy parts (like post-1950s car door handles, etc. ) that are primarily an electrolytic sacrificial electrolytic reaction especially in high humidity and salty environments (e.g. the UK.).
Or so I was taught at work in the car factory...
The modern "failure equivalent" is the sort of thing classic vehicle restorers meet when plastics simply fall apart as they were chemically designed to become brittle and the plastic actually decays after about 15 years... More pronounced with polypropylene parts on more modern cars... ? Many thermo-plastics and acrylics are used in place of the previous Zinc alloy parts, for weight and cost saving...
No wonder old cars get scrapped!
K2
"Zinc pest is not related to tin pest, and is also different from a superficial white corrosion oxidation process ("Weissrost") that affects some zinc articles".
I was only aware of the "white rusting" and corrosion blisters and pitting of (e.g.) chromed zinc alloy parts (like post-1950s car door handles, etc. ) that are primarily an electrolytic sacrificial electrolytic reaction especially in high humidity and salty environments (e.g. the UK.).
Or so I was taught at work in the car factory...
The modern "failure equivalent" is the sort of thing classic vehicle restorers meet when plastics simply fall apart as they were chemically designed to become brittle and the plastic actually decays after about 15 years... More pronounced with polypropylene parts on more modern cars... ? Many thermo-plastics and acrylics are used in place of the previous Zinc alloy parts, for weight and cost saving...
No wonder old cars get scrapped!
K2
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