[AJD] washing soda

[Duane Larson]

Steve,
Gosh, speaking as a physicist and appreciating your nice explanation I guess 
chemists maybe are ok...
Merry Christmas, and Best Regards,
Duane

----- Original Message ----- 
From: "Steve Treimer" <steelerhawk at yahoo.com>
To: "Antique John Deere mailing list" 
<antique-johndeere at lists.antique-tractor.com>
Sent: Friday, December 23, 2005 3:36 PM
Subject: Re: [AJD] washing soda


> David,
>  You were right on track too, just thought some might be interested in the 
> why not just the what.  Always helps me remember that way.  I thought some 
> more last night about it.  Wish I had the time to pursue the research, but 
> Duane can understand that too, right!
>  The cathode should be connected to the part needing to be derusted.  The 
> cathode is where the hydrogen is made when water is split into hydrogen 
> and oxygen.  Hydrogen actually serves two purposes here.  The primary and 
> most important purpose is to dislodge the rust and scale.  But also 
> there's another neat property of hydrogen that helps us too.  Something 
> that is bathed in hydrogen gas is in a "reducing" atmosphere.  Rust is 
> iron oxide, the oxygen that got to the iron part "oxidized" it.  That 
> opposite of oxidation is reduction, so by bathing the part in bubbles of 
> hydrogen, the hydrogen passivates the part, at least temporarily.  It's 
> too bad that we don't recovert that iron oxide back to iron, but this 
> would be a truly monumental feat.  But once the scale is off, the bare 
> metal comes out glistening clean because the hydrogen bubbles are 
> preserving the bare iron.  The high pH of the bath prevents oxygen from 
> forming at the anode which in turn allows hydrogen to be produce
> d at the
> cathode instead.  This is where the term "efficiency" kind of applies. 
> Actually, you're just changing the ingredients of this reaction to get the 
> product that you want - that is hydrogen bubbles at the cathode and no 
> bubbles at the anode.  If you were in an acidic bath, oxygen would come of 
> your anode quite readily when voltage was applied and long before any 
> hydrogen was ever produced at the cathode and all you'd do is 
> ruin/dissolve/oxidize the anode and the acid would be able to oxidize your 
> iron part even though it was connected to the cathode.
>  Sorry everyone is that is just TMI, just kind of fun revisiting the stuff 
> I let grow dusty in the closet I sometimes call a brain.
>  Have great holidays!
>  steve
>
> David Bruce <davidbruce at yadtel.net> wrote:
>  Steve,
> You did a much better job than I explaining things. Back in the old
> days lye was always Potassium Hydroxide but now it seems the term is
> used for KOH and NaOH both. (potassium hydroxide and sodium hydroxide).
> My thoughts is soda ash (washing soda) would provide a high enough pH
> but maybe sodium bicarbonate (baking soda) wouldn't when looking at
> electrolysis.
>
> David
> NW NC
>
> Steve Treimer wrote:
>
>>For electrolysis, the primary thing you need is an electrolyte to allow 
>>the charge to pass through the solution to work on the metal. This could 
>>be as simple as table salt depending on what your goal was.
>> For derusting electrolysis, baking soda would work just fine as an 
>> electrolyte, except the pH of the solution it produces when dissolved is 
>> fairly low. Someone was correct when they said the carbonate (not the 
>> bicarbonate in baking soda) is more alkaline/basic, i.e., it generates a 
>> bath that has a higher pH. Sodium Hydroxide (Lye) would produce an even 
>> more alkaline bath (higher pH). The only precaution you must use is that 
>> sodium hydroxide is aggressive enough to burn if you don't treat it with 
>> respect. It is referred to as a Strong Base in chemistry.
>>
>> Why do you want a high pH solution from a strong base to do this job? 
>> Efficiency is the correct answer, but I'll explain. Oxygen is produced at 
>> the anode. Hydrogen at the cathode. If you understand how these are 
>> produced from the splitting of water, you see that how easily it is made 
>> depends on how acidic the bath is (how much H+ ion is in there for those 
>> that care). You don't want oxygen to be made easily when doing this 
>> procedure. It reduces your electrolysis efficiency. So the higher the pH 
>> the better. If I were doing it, I too would use regular old Lye and just 
>> use care with it and make sure my kids knew it was off limits.
>>
>> Hope it helps.
>> Steve
>>
>>
>>DAVID BRUCE wrote:
>> Not really being familiar with a 'Hot Tank' solution I risk going out on 
>> a
>>limb but ...
>>Probably the hot tank solution is basically lye (potassium hydroxide or
>>sodium hydroxide) in solution. If that is true, the hydroxide solutions
>>are "stronger" than Washing Soda (sodium carbonate or soda ash) but other
>>than taking the appropriate safety precautions I would think it will work
>>as well for the electrolytic rust removal. Now using washing soda in a
>>'Hot Tank' might not work as well. Just my opinion with a significant
>>lack of information - ymmv - and I'm sure there are others here that have
>>more practical experience than I do.
>>
>>David
>>NW NC
>>
>>
>>
>>>Possibly a dumb question,
>>>
>>>So is Soda Washing similar to a 'Hot Tank'
>>>solution? Or will it remove rust as well? This
>>>sounds like something I need to try...
>>>
>>>Chris
>>>
>>>
>>>
>>
>>
>>
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