Questions tagged [metallurgy]
Chemical and physical characteristics of metals and alloys.
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Why does the reaction with copper and nitric acid change with concentration? [duplicate]
Depending on the concentration of nitric acid, copper undergoes two distinct reactions. For dilute concentrations of nitric acid, the reaction is
$$3\text{Cu}+8\text{HNO}_3\rightarrow 3\text{Cu(NO}_3\...
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0answers
55 views
Brass - is this corrosion or oxidation and why did it happen?
I have bought a new brass Y-split water valve which is plain brass but inside is a more polished one, it was packed nicely and I opened it 2 days ago, washed it off with water for some reason, then ...
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1answer
116 views
What exactly is the parasitic white layer that forms after iron parts are treated with ammonia? [closed]
I have little to do with chemistry and my only background is the inorganic chemistry I learned at school when I was 13-14 years old.
I need to have a basic understanding of the nitrating process (for ...
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34 views
Eutectic Phase Diagram of Al-Si Analysis
Hello,
How can I know from this phase diagram:
1. The composition of the alloy Al-Si that allows precipitation to occure?
2. The range of temperatures where the Al-Si is soluble?
3. The range of ...
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1answer
34 views
Can gold cause tin or other metals to corrode?
I stumbled upon the following article while trying to identify some old RAM modules:
https://www.techrepublic.com/article/quickly-identify-ram-chips-with-these-tips/
In the article, it mentions the ...
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1answer
42 views
Substitute molten salt bath with temperature range from 400–500 °C
I'm looking for a suitable substitute for a $\ce{NaNO2/KNO3}$ salt bath (for quite obvious reasons due to the other applications of the latter chemical). The salt mixture needs to have around 400 to ...
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1answer
53 views
Should I plate cast iron with copper first before nickel plating?
I have some antique handplane lever caps I would like to retore back to their former glory. They are made of nickel plated cast iron. The plating pin holed and flaked in areas, creating rust spots.
...
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3answers
685 views
Are risks (hexavalent chromium) during Chrome plating temporary, or remain with the product?
Since some chrome plating production processes generate hexavalent_chromium compounds, which are reportedly highly toxic/carcinogenic, I wonder:
Do the hexavalent chromium substances only occur (...
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1answer
30 views
How is traditional thermite powder stored such that it doesn’t corrode?
I watched some guy talk about redox reactions. Then he was going to do the good old thermite demonstration. He just had a bottle of thermite mixture. I’m wondering, why didn’t it have a chance to ...
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2answers
152 views
Different formulas for copper pyrites and bauxite
In my book in the chapter on General Principles and Processes of Isolation of Elements, I found that the formula for copper pyrites was stated as $\ce{Cu2S.Fe2S3}$ at one place, $\ce{CuFeS2}$ at ...
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What are Technetium's physical stress characteristics?
I've looked at periodic and data tables from several sources, but none give mechanical / engineering property data on Technetium. Why is this?
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0answers
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Can hexavalent chromium be created by exposure of chromium alloys to air at room temperature?
I believe that Cr on its own (as in chrome coating) oxidizes as Cr(III) when exposed to air, and similarly I think that it is the same for Cr as a component of stainless steel.
Is it always the case ...
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1answer
610 views
What is the black slag formed when sterling silver is melted with borax? [Edited with images]
What is the black graphite looking slag that is formed when sterling silver is melted with borax? Is there a way to remove it from the surface of the sterling silver? It appears to be indestructible!...
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0answers
46 views
Is awaruite to nickel sulfate possible?
Much time has passed since my basic chemistry and I am trying to determine if an awaruite mine proposed by FPX Nickel Corp ("FPX") might serve as feed-stock to nickel sulfate for battery production.
...
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0answers
37 views
Lead's affinity for oxygen in the cupellation refining process
My inorganic textbook says
Cupellation is a process, where crude gold is taken in a small bowl called cupell and melted in the presence of air. Due to high oxygen affinity of Pb, it is converted to ...
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1answer
55 views
How can I make an alloy wetter?
I'm trying to make a Bismuth-Indium based low-melt alloy wetter (specifically, better at wetting to solid metals and glass). I've tried adding gallium, which obviously works, but due to its metal-...
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2answers
83 views
How does Nickel harden steel?
Nickel :
Does not harden austenitic stainless steel
Ease the tempering of martensitic stainless steel
Harden maraging steel by forming precipitates
I also read people saying that it harden ferritic ...
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1answer
103 views
Effect of oxidation aluminium reflectivity
Aluminium is a fairly good reflector, but oxidation will reduce it's optical reflective properties.
Aluminium is used for reflectors either being deposited on a substrate, or polished and protected ...
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0answers
152 views
Find alloy composition by density
I have a square piece of metal from a processor heat sink that looks a lot like copper. I'm trying to find the alloy composition but I'm not sure how.
I happen to have both a digital caliper and a ...
6
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1answer
1k views
Why is the ore generally converted to an oxide and then reduced? [closed]
In the elementary extraction of metals from their concentrated ores, why is the ore generally converted to an oxide, and then reduced? Why is the reduction of these metal oxides easier than the other ...
4
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1answer
144 views
Which karat gold is harder, 24 kt or 18 kt?
$\pu{24 kt}$ gold indicates that $24/24$ part of it, i.e. $100\%$ of it is gold. $\pu{18 kt}$ indicates that $18/24$ part of it is gold. As gold is a soft element, I reckoned that $\pu{18 kt}$ gold ...
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2answers
246 views
Forging steel inside a zero oxygen environment
Intro: I have watched one too many blacksmithing videos and now I have a question: is it possible to forge steel (either just reshape or "forge-weld") inside a no-oxygen environment?
Scenario: ...
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1answer
5k views
Will we ever run out of gold, silver, copper and other important conductors? [closed]
Conductors are very important in technology. At the current rate of extraction how long until the world's reserves of copper are depleted?
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1answer
190 views
Extraction of metals using electrolysis
I came across a question that goes as:
The electrolytic method of reduction is employed for the preparation of metals that are:
Less electropositive
Moderately electropositive
Highly ...
7
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0answers
60 views
What is required to achieve 999.9999 or finer gold?
After doing some research on gold purity, I found that the current record of gold fineness is at an astounding 999.999 fine achieved by the Perth Mint, Australia 1957. However, I could not find any ...
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1answer
299 views
How can we separate a mixture of two sulphide ores using froth floatation method? [closed]
As we know froth floatation method makes use of the wetting properties of mineral particles.
Mineral particles (sulphide) become wet with oils, while gangue particles get wet by water
According to ...
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1answer
52 views
Thermal oxidation of gold(I) sulfide
As far as I know the chemistry of $\ce{Ag}$ and $\ce{Au}$ are almost the same; because $\ce{Ag}$ belongs to the 4d series and $\ce{Au}$ belongs to the 5d series, we know the size of 4d and 5d are ...
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1answer
81 views
Is it possible to dissolve gold in zinc?
I know you can dissolve gold in mercury, but i do not have access to any. Would it be possible to dissolve it in molten zinc instead mercury.
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53 views
What metal is used to back this mirror?
My father is attempting to remove the mirror from a piece of glass. We stripped the black paint from the back and exposed the shiny surface with acetone. In the past he has been able to remove ...
2
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1answer
250 views
Froth floatation process - Use of stabilizers in froth floatation method
How exactly do the stabilizers affect the process of Froth floatation method? I mean how do they stabilize the froth in the process?
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1answer
35 views
How would ceramic coating inside the reactor affect heat transfer? [closed]
With the ceramic coating, would I be able to get its internal temperature raise upto 520.
I would like to get a reactor fabricated for plastic pyrolysis. The temperature would maintained around 520C. ...
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1answer
26 views
Paint removal from metal [closed]
What chemical product works well to strip paint off to reveal bare metal in this instance a small tin (guessing to be aluminium or steel) with as good a finish as possible.
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1answer
86 views
How to separate platinum from steel?
I'm currently extracting some platinum from an electrode. One part seems stuck in some way (possibly welded) to a piece of steel. I'm guessing it's steel because it's magnetic. I did a heat test on ...
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1answer
49 views
What is the reason behind the 2% increase in silver metal composition just after melting the raw silver alloy (55% silver)? [closed]
I determined the silver composition from an alloy obtained from a jeweler to be 55% and wanted to extract silver out of it. However, upon melting around 5 kgs of alloy, the silver composition went up ...
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0answers
169 views
Refining Tin (Sn)
I am a Copper Cookware Tinner & have a problem in reusing much of the tin that I end up sweeping off the floor etc. Prob about 5kg over the year & it would be great to save this?
Now, my ...
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0answers
58 views
Copper pyrite representation [closed]
What is the oxidation state of iron in $\ce{CuFeS2}$? And also could you please tell it's proper representation: $\ce{Cu2S.FeS.FeS2}$ or $\ce{Cu(I)FeS2}$?
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1answer
1k views
Why is ZnO reduced in this reaction?
Consider the following Ellingham diagram.
At 673K, the Gibbs energy value of oxidation of Zn is more negative than the Gibbs energy value of oxidation of C (coke). So, Zn should be oxidised to ZnO. ...
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2answers
292 views
Brass Instrument: Dezincification or just scrubbed off?
I do own a brass instrument (a trombone). The lacquer is damaged.
I asked how to deal with it here.
Now I learned that the brass contains zinc, and there is a corrosion process called "...
2
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1answer
201 views
Zinc Sulfate Purification
In the process for electrolysis for zinc, three things must be done:
Leaching the ZnO
Purifying the ZnSO4 by means of cementation
Performing the electrolysis
However, step 2, as it is presented by ...
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0answers
107 views
How nickel plated copper strip can be welded? What is the optimum thickness of nickel layer?
I have a trouble with (resistance) spot welding of nickel plated copper strip to 18650 battery. I tried to weld 0.1mm, 0.2mm and 0.3mm copper strips with 5 micrometers and 10 micrometers nickel plate ...
13
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2answers
651 views
Ellingham Diagram
My textbook says the following about the Ellingham diagram:
Each plot is a straight line except when some change in phase ($\ce{s -> liq}$ or $\ce{liq -> g}$) takes place. The temperature at ...
2
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1answer
112 views
How to differentiate magnetite from metallic iron?
Both metallic iron and magnetite, $\ce{Fe3O4}$, are magnetic. Now, iron is grey in color, whereas hematite is black, so that they can be distinguished visually.
Now, I have a powdery mixture of iron/...
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1answer
147 views
Does carbon monoxide form or carbon dioxide forms when carbon reduces metal oxide?
I would like to discuss this in context of ellingham diagrams.
When $\ce{C -> CO}$ line is below metal oxide line, CO is produced.
Similarly, in other case $\ce{CO2}$ is produced.
But when both ...
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0answers
44 views
Iron-platinum refining
If I have an iron-platinum alloy, can I put this into a solution of $\ce{HCl}$ to dissolve the iron, leaving a $\ce{Pt}$ precipitate?
I know that Fe dissolves in $\ce{HCl}$ to form $\ce{FeCl2}$ and $\...
2
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1answer
412 views
What does negative current reading in galvanic couple mean?
I used a multimeter in a galvanic testing between two metals. I connect one to metal A and the another end to metal B. Then I immersed the 2 metals in a salt solution, securing that they are apart in ...
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1answer
63 views
What is the shiny structure under a metal coating?
I performed a hot dip aluminizing on steel for 15 seconds. Then, after I bent the steel to remove the coating easier, the steel under was rough, shiny, and metallic, and was different from the ...
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1answer
79 views
Which corrodes faster at 5% NaCl solution at room temperature: Steel or Aluminum? [closed]
Which corrodes faster at 5% NaCl solution at room temperature: Steel or Aluminum? Is it true that Al has high corrosion resistance? Or is it just a myth as stated in this article.
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1answer
44 views
What can be a metal cleanser for aluminum?
I want to remove corrosion products in aluminum, but I don't have supply of nitric acid, as suggested by an ASTM method. Which can be a good substitute?
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1answer
535 views
Aluminum to prevent Iron corrosion
I have heard of how zinc is used to prevent corrosion of iron. So why not use aluminium coat instead? After all Aluminum oxide forms a stable coat over the surface.
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1answer
57 views
Is it possible to have negative corrorion rate and weight loss, meaning specimen [steel] gained weight after immersion in electroyte solution?
Regarding this article, I have read that the corrosion rate and weight loss of a steel specimen after immersion in different corrosive media is negative. I'm surprised that this is really possible. Is ...
