Firimor
Harmless
Posts: 1
Registered: 17-9-2005
Member Is Offline
Mood: No Mood
|
|
Help me
Hey guys, i just bought a new cheap ass pewter ring and put it in some HCl to see what happens. I was hoping it would remove some of the oxidation,
but it ended up taking away all the shine and made it look more tarnished than ever.
I currently have two theories:
1. The HCl dissolved some kind of coating that made the metal shiny, and nothing can reverse process
2. Some kind of precipitate was formed that coated the ring, making it appear black, and there may be a way to remove new substance.
I don't have time right now to look all over for some kind of reaction, so I was hoping that you guys, with your vast knowledge of chemistry,
could identify the problem and possibly find a solution to bring my ring back to normal.
All I can tell you after running a wikipedia search is that pewter consists mainly of tin. The rest consists of a mixture of copper and either
bismuth or antimony. I dont think the tin or copper would have reacted at all, so it must involve the antimony or bismuth.
Thanks for the help.
|
|
|
neutrino
International Hazard
Posts: 1583
Registered: 20-8-2004
Location: USA
Member Is Offline
Mood: oscillating
|
|
I'm betting it was #1. Have you tried scrubbing at it to make sure it isn't #2?
|
|
|
Fleaker
International Hazard
Posts: 1252
Registered: 19-6-2005
Member Is Offline
Mood: nucleophilic
|
|
It was probably the antimony and the tin, both of which take time to dissolve in cold HCl.
Bismuth and copper won't react with cold HCl to my knowledge.
|
|
|
The_Davster
A pnictogen
Posts: 2861
Registered: 18-11-2003
Member Is Offline
Mood: .
|
|
While doing my own experiments with antimony/tin alloys, as the tin dissolved the surface of the alloy would darken from the unreacting antimony left
on the surface. This was when dissolving the alloy electrolytically in HCl and I was able to collect a great deal of this antimony. For me I was
never able to simply dissolve this alloy in HCl, it would never react, but I guess the composition of our alloys are different and yours is more
reactive. The antimony coating on your ring will stain everything as it is very fine.
According to Braurer, antimony is insoluble in HCl, but my own experiance here differs, if any air is present and the antimony is very fine it will
dissolve rather well.
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
So yeah, you've etched it... chemical means are no good here, get a buffing cloth and do it the old fashioned way.
Tim
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
