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Re: baseplate differences


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11/8/2004 7:45 PM
Dr. Strangelove
Re: baseplate differences
Joe Gwinn wrote:
quote:
"Nickel Silver is prettier, though. A classic solution seems to be a stainless steel baseplate and a nickel silver cover."
All you need to do is figure out how to solder them.  
 
I haven't tried 2% silver solder but it might work.  
 
-drh  
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11/9/2004 7:04 AM
Joe Gwinn

[QUOTE]Joe Gwinn wrote: Nickel Silver is prettier, though. A classic solution seems to be a stainless steel baseplate and a nickel silver cover. All you need to do is figure out how to solder them.  
 
I haven't tried 2% silver solder but it might work.[/QUOTE]  
 
Nickel Silver solders like brass, I think, so regular Kester 44 flux ought to work, if the metal is clean and bright.  
 
I haven't tried 2% silver solder (the rest is tin and lead), but I suspect that for stainless steel a zinc chloride based liquid flux will still be needed, as described at length in a prior thread. I'll have to try the 2% silver solder; I've heard it's very nice to work with, albeit expensive.  
 
Just tin the place the ground wire will go, or the places where the cover will be soldered down, and clean all flux and residue off the baseplate before soldering the wire or cover down to the pre-tinned spot with radio solder. Use a powerful soldering iron (or gun), so the metal heats up quickly.  
 
If one uses a water-based flux (like Kester 331) core in the solder used for tinning (along with the zinc chloride flux), washing the tinned baseplate with hot water will remove all flux residues, without use of acetone or any such solvent.  
 
The radio solder flux need not be removed, except for appearance.  
 
One can also tin the nickel silver with these water-soluable fluxes, if necessary. Still need to wash the flux residue off with hot water.
 
11/9/2004 1:03 PM
Dr. Strangelove

Joe,  
 
Last time I bought 2% silver solder it was $20-25/lb.  
Not cheap, but not too expensive.  
 
Silver solder was originally intended for soldering to silver-plated wire without dissolving the plating. It also has a good affinity for other metals but the silicon content is usually what makes soldering to stainless steel more difficult.  
 
My google searches suggest that jewelry/crafts people are soldering stainless steel with special fluxes and tin/silver (96/4) solder.  
 
-drh  
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11/9/2004 9:01 PM
Joe Gwinn

On 11/9/2004 8:03 PM, Dr. Strangelove said:  
quote:
"Last time I bought 2% silver solder it was $20-25/lb. Not cheap, but not too expensive."
 
 
I'll have to try some, although the local elecronics store sells little hanks of 2% silver solder for too much. Silver is precious, but not *that* precious.  
 
quote:
"Silver solder was originally intended for soldering to silver-plated wire without dissolving the plating. It also has a good affinity for other metals ..."
 
 
That's my understanding too.  
 
quote:
"...but the silicon content is usually what makes soldering to stainless steel more difficult."
 
 
Silicon? I didn't think that stainless steel alloys had enough silicon in them to matter. What makes stainless steel stainless is the chromium and nickel. The chrome in particular forms a very tightly adhering and strong oxide, which protects the metal underneath. Unless this oxide layer is removed, soldering is impossible. The flux chemically removes the oxide layer.  
 
quote:
"My google searches suggest that jewelry/crafts people are soldering stainless steel with special fluxes and tin/silver (96/4) solder."
 
 
Yes. Those special fluxes are typically acidic, and are often more aggressive than the zinc chloride based tinners fluid (which also works).  
 
Tin/silver solder has the advantages of strength and good appearance, not darkening with age and exposure to sweat. The melting temperature is higher than for tin/lead/silver solders.
 
11/12/2004 10:38 AM
Dr. Strangelove

Joe Gwinn wrote:
quote:
"Silicon? I didn't think that stainless steel alloys had enough silicon in them to matter. What makes stainless steel stainless is the chromium and nickel. The chrome in particular forms a very tightly adhering and strong oxide, which protects the metal underneath."
 
 
Check Matweb.com for specifics. All stainless alloys have silicon in varying degrees.  
 
The tightly-adhering oxide occurs with zinc or galvanized plating. It is visibly white.  
 
Chromium oxides are highly colored, ranging red to orange-black, and are carcinogenic. If they occurred with any alacrity or frequency, we'd see them before we died from them.  
 
Soldering stainless is difficult because it is inherently inert compared to most other alloys.  
 
-drh  
--
 
11/12/2004 7:38 PM
Joe Gwinn

On 11/12/2004 5:38 PM, Dr. Strangelove said:  
[QUOTE]Joe Gwinn wrote:  
 
Silicon? I didn't think that stainless steel alloys had enough silicon in them to matter. What makes stainless steel stainless is the chromium and nickel. The chrome in particular forms a very tightly adhering and strong oxide, which protects the metal underneath.  
 
 
Check Matweb.com for specifics. All stainless alloys have silicon in varying degrees.[/QUOTE]  
 
It's true that many steel alloys have silicon in them, and transformer iron can contain a lot of silicon. Still, that's not why stainless is hard to solder.  
 
quote:
"The tightly-adhering oxide occurs with zinc or galvanized plating. It is visibly white."
 
 
Zinc Oxide is a loosely adhering white powder, but what does that have to do with chromium and nickel oxides?  
 
quote:
"Chromium oxides are highly colored, ranging red to orange-black, and are carcinogenic. If they occurred with any alacrity or frequency, we'd see them before we died from them."
 
 
Chromium oxide, if pure, is almost colorless. Perhaps it's a bit blue, as stainless steel is bluish. Nor is it a poison, or we would have all died from stainless-steel cookware.  
 
quote:
"Soldering stainless is difficult because it is inherently inert compared to most other alloys."
 
 
Stainless steel is inert only in the presence of oxygen. In an anoxic environment, stainless steel will rust. The classic example is stainless steel screws in wet wood, typically below the waterline in a wooden boat: stainless steel screws are soon reduced to nubs. The standard solution is to use silicon bronze hardware in such places. Up in the air, stainless steel works quite well.  
 
Going in the opposite direction, there is passivation of stainless steel, where one exposes the steel to nitric acid. After some gassing, it goes quiet, and the corrosion resistance of the stainless steel is greatly enhanced. Basically, it seems that the acid has removed all the iron from the surface, leaving pure nickel and chrome, which both have tightly adhering oxides.  
 
An even greater contrast is Gold, which does not form an oxide under normal conditions, and is very inert, dissolving only in Aqua Regia (a mixture of nitric and hydrochloric acids), and yet is easily soldered with ordinary rosin fluxes.
 
11/12/2004 11:44 PM
Dr. Strangelove

Joe Gwinn wrote:
quote:
"Chromium oxide, if pure, is almost colorless."
References, please. Be specific as to valence. This is chemical history for 60 consecutive years of the CRC Handbook of Chemistry and Physics where all listings of chromium oxides, hydrated or not, are highly colored.  
 
See MSDS for CrO, CrO2, Cr2O3, and CrO3.  
 
-drh  
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