Cleaning Brass, Copper or Bronze

[gordiesgirl]

Very cool, thanks

[sheriobailey]

WOW

[ERnurse]

I think those guys on Mythbusters, got out of jail using chili sauce. It ate thru the bars or something.

[EPC Guy]

Originally Posted by abmm

Sorry for dredging up the necropost... didn't see the need to create a new thread.

We find a LOT of spent rifle, machinegun and pistol cartridges in our travels. Usually they are badly tarnished and we often need to see the data stamped on the base in order to positively identify them.

I did a bit of research on the net and discovered that nuclear chilli sauce (burns twice ) is a great cleaning agent for old brass and other metals. after cleaning, I chucked all of our rare brass into a container and covered it with "Fire in the Hole" brand chilli sauce overnight.

I washed em th enext morning and discovered to my dismay that the sauce had stripped out a component of the brass alloy leaving what looked like a copper cartridge case. Very disappointing! But the data on the base of even the cruddiest .30 M1 carbine shell is now readable. A big lesson learned here was to maybe use ONE less rare shell to test it out rather than a whole container full.

After witnessing how effective the chilli sauce was I found myself thinking "And we eat that stuff?!?"

I'm still experimenting with the right amount of time to leave brass in this stuff. So I'll post my results when they come to hand.

...must be the juice from the peppers...think I'll try experimenting with jalapenos, serranos, etc.

[Tn Dirt Digger]

Good Info....Thanks for taking the time to share that.

[Deefburger]

Originally Posted by abmm

Sorry for dredging up the necropost... didn't see the need to create a new thread.

We find a LOT of spent rifle, machinegun and pistol cartridges in our travels. Usually they are badly tarnished and we often need to see the data stamped on the base in order to positively identify them.

I did a bit of research on the net and discovered that nuclear chilli sauce (burns twice ) is a great cleaning agent for old brass and other metals. after cleaning, I chucked all of our rare brass into a container and covered it with "Fire in the Hole" brand chilli sauce overnight.

I washed em th enext morning and discovered to my dismay that the sauce had stripped out a component of the brass alloy leaving what looked like a copper cartridge case. Very disappointing! But the data on the base of even the cruddiest .30 M1 carbine shell is now readable. A big lesson learned here was to maybe use ONE less rare shell to test it out rather than a whole container full.

After witnessing how effective the chilli sauce was I found myself thinking "And we eat that stuff?!?"

I'm still experimenting with the right amount of time to leave brass in this stuff. So I'll post my results when they come to hand.

You have a couple of things going on here. Chilli sauce has Salts, usually clorides of sodium, calcium, and potassium, as well as Acid, as acetic acid and ascorbic acid, (Vinegar and Lemon). The copper color on the surface could be nacent copper that was re-deposited when the copper oxides and copper salts in the corrosion were converted back to metal. This will leave a thin layer of pure metal on the surface. Since Brass is an alloy of copper and tin and zinc(Bronze too), then any reaction that leaves metal behind, will leave a metal that is a different color than the alloy. In this case, the tin/zinc was removed, as a salt, leaving the copper behind. Buffing will remove this surface layer.

On the other hand, because Chilli Sauce is so caustic, You may have removed a layer of metal plating. I think this is unlikly though, because there is no reason I can think of to plate Copper with Brass. First off, you can't effectively electroplate an Alloy like brass. The different metals making up the alloy behave differently in the plating process and will not form the same alloy on the target piece. And second, It would make the part more costly to produce.

Buff out the coppery portion of one of your pieces with Jewlers Rouge and I bet you get Brass under the Copper coating.

I do not recommend cleaning with Chilli Sauce! It's WAY more chemically active than you might think. Just because you can eat it dosn't mean it isn't corrosive. White vinegar, baking soda are fine for metals so long as you are planning to polish them. If you are not going to polish them, then you are better off using solvents. If the piece is painted, and you intend to preserve it, then your only option is to use mild soap in distilled water.

To remove grease and wax, the method is to use what is known as the solvent chain.
That is, Methanol, then Acetone, then MEK or Methel Ethel Ketone.
Follow this with a dip in HOT TSP and Distilled water solution to remove any grime left behind when the solvent chain removed the oils, waxes, and grease. Then rinse in Distilled water. All that will be left on the surface after this process is insoluable salts, oxides, and metal.

You have two choices for the remaining surface contaminates. Caustics, and elbow grease. The caustics need to be chosen carefully depending on the metal. Some metal alloys, like brass, form soft salts, and oxides, and so a little elbow grease and a mild abrasive will usually do the trick.

For Caustics, be careful. Some metals will get worse in caustic solution, especially when there is more than one kind present! For instance, if there is lead present in a tin lead solder joint, then the lead may form an insoluable salt stain on the piece you are trying to clean, and it won't come off easily! Lead is soft, it's salts are soft, but they are also dark and will fill the little micro pits and scratches in the surface of the piece and stain it dark. They are also sticky. Lead is especially troublesome.

Acid is used to convert oxides. Bases are used to convert Salts. Start with Vinegar, If the corroded area gets darker and the bare metal area remains light, then you are probably ok. The darkening is from the metal being freed of the oxygen and it will lighten up with buffing. If the bare metal is darkening, then you must stop and rinse, and go to a base instead. For a base, start with baking soda. All sodium compounds are water soluable. So, anything the baking soda leaves behind will be in solution. The other part of it is carbonate. This will most likely gas off and bubble out of the solution.

The best metal cleaner I know of is Hydrogen. Heating a metal up in a bubble of hydrogen will clean it up RIGHT NOW! Problem is you gotta get it really hot, and you have to have a steady supply of hydrogen.

Distilled Water is probably the safest thing you can use. It's both an acid and a base, and if you can introduce constant stirring or ultrasound, it will remove darn near anything, just slowly.

That's my two cents

[abmm]

Cool, thanks for the advice Deefburger, you have just made our job easier when it comes to preserving our finds correctly.

Cheers.