[Delta p]

My concern relates to the practice and effectiveness of cleaning gun barrels with 3% Hydrogen Peroxide. The folks that I've contacted at a peroxide manufacturing plant and my searches on the internet so far have not produced any answers...

My question pertains to the effect that stabilized 3% Hydrogen Peroxide has on Lead, when combined at ambient (appx. 75 F) temperature. A crude experiment of my own, involving placing a small (1g) oxide-free Lead shaving in a ceramic crucible and covering with appx. 2oz of Hydrogen Peroxide, resulted in about 36 hours of "activity" wherein the Peroxide bubbled vigorously on the surface of the Lead. At the end of this time period the Lead showed no visible signs of oxidation, and still weighed 1g. (my scales are crude...+/- 0.1) The assumption is that the gas given off during this reaction was Oxygen, the how and why is a mystery to me.

My contact at the manufacturing plant informed me that Hydrogen Peroxide, at concentrations <8% will be catalyzed by Lead, and at concentrations >8%, will, conversely, oxidize the Lead. This makes no sense to me. First of all, doesn't a calalyzing reaction require three components, (a catalyst and two reactant compounds) The combination of Lead as a catalyst, and Hydrogen Peroxide as a single reactant, doesn't meet this criteria. Secondly, the explanation that the reaction (whatever kind it may be) completely "reverses" itself, based on the concentration of the Peroxide, seems uh....unlikely.

Any help in understanding what is actually happening would be greatly appreciated.

Thanks,
Bob Dahler

[Mitch]

The reaction is H₂O₂ ---> (1/2)O₂  +  H₂O

Lead would be the catalyst for this reaction. I'm not sure what the reaction would be if H2O2 is greater than 8% you'll probably be making lead oxide.

[jdurg]

Mitch is correct.  Not ALL reactions are A+B -> AB.  Decomposition reactions are very common and are AB -> A + B.  Hydrogen peroxide is not all too stable, so all it takes is a metal or metal ion to catalyze its decomposition into water and oxygen gas.  (The peroxide will decompose on its own, however, but at a much slower rate.  That is why the caps for H2O2 bottles are vented.  It's to allow any built up gas to escape).  

At low concentrations, the amount of oxygen produced and the rate at which it's produced isn't that high.  When you start increasing the concentration of hydrogen peroxide, you increase the amount of oxygen that's produced and the temperature of the reaction.  (Since the decomposition is exothermic, which means that it gives off heat).  So when you reach a certain concentration, the temperature of the system becomes quite high and the presence of oxygen is high as well.  At this point, it's thermondynamically favorable for the lead to combine with the oxygen.  So at >8% the lead is still catalyzing the decomposition of H2O2, but it is then going on to react with the oxygen that is produced.  Henced the lead becomes oxidized.  

[Delta p]

I never imagined that the thermodynamics of the exo-reaction was the key. Just for clarification; if one were to use, for example, 50% H-Peroxide combined with Lead and maintained a low temperature of RX with a chiller...there would be no (or little) Lead Oxide formed?

Regardless, would it be safe to say, H-Peroxide (in the garden-variety 3% concentration found in the health & beauty section at Wal-Mart) is ineffective at removing Lead deposits from a gun barrel, even though it "fizzes" a lot?

[jdurg]

I never imagined that the thermodynamics of the exo-reaction was the key. Just for clarification; if one were to use, for example, 50% H-Peroxide combined with Lead and maintained a low temperature of RX with a chiller...there would be no (or little) Lead Oxide formed?

Regardless, would it be safe to say, H-Peroxide (in the garden-variety 3% concentration found in the health & beauty section at Wal-Mart) is ineffective at removing Lead deposits from a gun barrel, even though it "fizzes" a lot?

Possibly.  But remember, at 50% concentration there will be a LOT of oxygen gas generated as the peroxide decomposes.  Plus, even though it will be at a low temperature, the reaction itself will still generate a lot of heat right at the surface which will lead to some oxidation.  For the 3% part of your question, H2O2 still may be effective in that the effervescence of the decomposing peroxide may loosen up particles which are 'stuck' to the gun barrell, thus allowing an easier cleaning.  Also, the melting point of lead is quite low compared to the metals that guns are made out of, so you could probably melt out any lead by heating the gun up.  (Unloaded, of course.   )  

[Delta p]

For the 3% part of your question, H2O2 still may be effective in that the effervescence of the decomposing peroxide may loosen up particles which are 'stuck' to the gun barrell, thus allowing an easier cleaning.

FWIW : The goal here is to remove lead that has essentially been burnished under very high temperature and pressure into the steel of the barrel. The simple removal of loose particles that might be affected  by a mild effervescent action is not the problem... This "top layer" of crud is easily removed by wiping with a patch, regardless of the liquid used.  

 

Also, the melting point of lead is quite low compared to the metals that guns are made out of, so you could probably melt out any lead by heating the gun up.  (Unloaded, of course.   )  

Cleaning a gun is something that is done every time it has been shot. In my case, that equates to about once a week, so this melting operation, with all it's associated problems, would be impractical. Another major concern, would be the certain destruction of the firearm if this operation was executed... even once. Gun steel is tempered, and the uncontroled heat employed in melting the lead out of a barrel would certainly ruin the steel, rendering the gun useless.

[FISHEYE]

Bob,
the best way to clean gun barrels is to use safety-kleen immersion cleaner in a ultrasonic tank,dont let it sit in the solution for more then 10 min its very corrosive to anything but steel or iron,lead,carbon,it all will dissolve,i use it to clean out supressors.