Cleaning Metal Samples.

[Guest StrontiumRed]

Hi,

 

Firstly hello everyone. I can't believe it's taken me so long to discover this site, I've been collecting elements for about 18 months and could have exchanged views with others ages ago.

 

I was wondering how I might best clean up some of my samples that are starting to look a bit tired. Worst offenders are Y, Sm, Gd and Tb Metal. (Interestingly From Dy to Lu the samples have hardly deteriorated at all, and my La, Ce, Pr, Nd and Eu are under mineral oil). What substance would best remove the oxide that forms on these lanthanides?

 

Thanks,

 

SR.

[jdurg]

Some elbow grease and some fine grain sandpaper would probably be the best thing. It's a good idea to store Samarium under mineral oil as well, since although it doesn't oxidize nearly as quickly as La, Ce, Pr, Nd, and Eu do, over time it does develop a nasty layer of oxidation. It also reacts slowly with water, so you don't want to put any water on the surface of it. Therefore, the best solution is to take some fine sandpaper and polish them up a bit, or use a soft brush on a dremel tool and polish them up like that.

[akcapr]

i know hcl clean coppoer really well- possibly for some of those.

[collector]

I once tried to clean a piece of neodymium. The metal is easily etched with diluted HNO3, and the surface is cleaned with water, and dried with acetone. Immediately after, I polished the surface with polishing compunds, resulting in a mirrorlike surface finish. But there the luck stopped.

I immersed the shiny metal under paraffinum oil, but the metal corroded heavily within years. Nothing could stop the corrosion on depth. Even sodium behaves (and is preserved) better than Nd for a long time immersed under paraffinum oil!

 

When I purchased the lanthanide metals from David Hamric (eBay, "rare earth metals set"), I observed the same problem within a year. Finally, I solved that problem by simply purchasing La,Ce,Pr,Nd and Eu as metal pieces in sealed glass ampoules under argon gas (most of these also from Hamric).

 

My experience is that the reactive lanthanides should be kept under Ar in sealed glass ampoules. These metals should NOT be kept under paraffinum oil, at least not for an element collection.

The heavier lanthanides (from 66 Dy up to 71 Lu) does not corrode in air.

Sm corrodes slowly, and the commercial metal is often oxidized on the surface.

Gd also (and to some extent Tb), but much slower.

[collector]

The purity of the metal is important!

I have some zinc rods and copper foil of analytical purity. These samples does not show any surface oxidation when stored in air.

But technical grade pieces of the same metals are rapidly oxidized under the same conditions!

 

Purity is vital.

[JoyZhong]

I once tried to clean a piece of neodymium. The metal is easily etched with diluted HNO3, and the surface is cleaned with water, and dried with acetone. Immediately after, I polished the surface with polishing compunds, resulting in a mirrorlike surface finish. But there the luck stopped.

I immersed the shiny metal under paraffinum oil, but the metal corroded heavily within years. Nothing could stop the corrosion on depth. Even sodium behaves (and is preserved) better than Nd for a long time immersed under paraffinum oil!

 

When I purchased the lanthanide metals from David Hamric (eBay, "rare earth metals set"), I observed the same problem within a year. Finally, I solved that problem by simply purchasing La,Ce,Pr,Nd and Eu as metal pieces in sealed glass ampoules under argon gas (most of these also from Hamric).

 

My experience is that the reactive lanthanides should be kept under Ar in sealed glass ampoules. These metals should NOT be kept under paraffinum oil, at least not for an element collection.

The heavier lanthanides (from 66 Dy up to 71 Lu) does not corrode in air.

Sm corrodes slowly, and the commercial metal is often oxidized on the surface.

Gd also (and to some extent Tb), but much slower.

Hi just want to ask, I've bought Nd ingot also ,but they come in small pieces (5mm-10mm) and was previously immerse in certain kind of mineral oil. so there's a dark surface on the metal, is there any chemical that can wash away this dark surface without hurting Nd metal itself too severely? I've thought about diluted HNO3, but just afraid the Nd will react with it and won't left me anything behind, cause my Nd ingots are quite small.

[studiot]

I would try in this order.

The organic solvents can't damage the metal itself.

 

Petroleum?

Petroleum-ether?

 

Acetone?

Cellulose paint thinner.

 

Jenolite (phosphoric acid metal surface cleaner?

Brasso metal polish?

Silvo metal polish?

 

 

Note this thread is ten years old.

Edited September 11, 2015 by studiot

[Sensei]

The organic solvents can't damage the metal itself.

How come?

f.e. acetic acid is organic polar solvent.

And with many metal it's going into reaction creating acetate.

f.e.

Zn + 2CH₃COOH-> Zn(CH₃COO)₂ + H₂

(This one is pretty slow at room temperature)

If there is reaction between metal and solvent, then how come it's not "damage of metal".. ?

 

Hi just want to ask, I've bought Nd ingot also ,but they come in small pieces (5mm-10mm) and was previously immerse in certain kind of mineral oil. so there's a dark surface on the metal, is there any chemical that can wash away this dark surface without hurting Nd metal itself too severely? I've thought about diluted HNO3, but just afraid the Nd will react with it and won't left me anything behind, cause my Nd ingots are quite small.

If you will polish, or do whatever you can to remove oxide layer, and leave on air again, it will go into reaction with oxygen sooner or later..

 

Quote from

https://en.wikipedia.org/wiki/Neodymium

"Metallic neodymium has a bright, silvery metallic luster, but as one of the more reactive lanthanide rare-earth metals, it quickly oxidizes in ordinary air. The oxide layer that forms then peels off, and this exposes the metal to further oxidation. Thus, a centimeter-sized sample of neodymium completely oxidizes within a year"

 

ps. There is needed such solvent which reacts with oxide layer, but not with metal alone.

Edited September 11, 2015 by Sensei

[studiot]

 

How come?

f.e. acetic acid is organic polar solvent.

And with many metal it's going into reaction creating acetate.

f.e.

Zn + 2CH₃COOH-> Zn(CH₃COO)₂ + H₂

(This one is pretty slow at room temperature)

If there is reaction between metal and solvent, then how come it's not "damage of metal".. ?

 

 

 

Thank you for the correction, Sensei.

 

I really should have said non polar solvents which I listed (which all happen to be organic).

 

That is why listed them first.

 

I don't recall listing acetic acid or any organic polar soubstance, any more than I recall the questioner listing zinc, a fairly reactive metal.

 

Neodymium is also a reactive metal so any cleaning method is going to remove some metal: the objective must be to minimise this.

 

My remarks are adressed to today's question only, in post#6.