New here, but not so new to shooting, handloading, and electrochemical bonding.
Non-identical alloys, atmospheric moisture, and the presence of acidic/alkaline intervening coatings can produce a bond between the two dissimilar metals. It literally interchanges ions between the two alloys, and some pretty sturdy bonds can result.
To understand the process, look up how dry or wet cell batteries do their thing. Pretty much the same thing occurs when we assemble ammunition. In my own case, I've seen it with cases tumbled in walnut dampened with some dilute CLR as a cleaning additive, and also when doing sonic cleaning with Lemishine. The cases retain some acidic coating and when the bullets are seated the bonding begins immediately; slowly, and sometimes not so slowly.
I occasionally broke down a randomly selected cartridge from storage using my RCBS collet puller. On occasion, the bullets are so firmly bonded that they come out with actual cartridge brass bonded directly to the bullet. It's not a welding process so much as an electrochemically driven ionic transfer process.
Since my discovery of this, I no longer use any overtly acidic or alkaline products in my case cleaning processes, and am slowly researching a way to interpose a dielectric barrier between brass and copper on my ammunition making.
Another description of the process is bimetallic corrosion.
Researching the sonic cleaning process, I learned that additives like Lemishine, etc., really aren't needed. The ultrasonic agitation actually breaks down water into a vapor at the interface between the water and the brass. The resulting surface is as clean as it would have been after treatment with soldering flux. In some ways, the cleaning process is really much like steam cleaning. If one simply must use a cleaning agent, a simple drop or two of Dawn is literally all you need.
The problem can result in over-cleaning, where all oxidation is stripped off the brass; thus sensitizing it to the ionic transfer process.
My goal is to find a liquid additive to the rinse water that leaves a very thin dielectric coating on the brass, thereby insulating the brass from electrochemical ionic transfer.
NASA developed Teflon as an intervening coating or mechanical device to prevent a process known as vacuum welding. Though different in nature, it achieves bonds very similar to what we see between bullets and case necks.
The only issue I worry about when considering Teflon as the intermediate coating is whether or not some necessary chemical will have a negative effect on the propellant.
Greg
PS Jrod, I just caught up reading the other posts and saw your reference to Imperial dry lube. Thanks to you. I probably have my solution.
I did so when I got to thinking about how insignificant "spit necks" are.
