The bottom rim is where an aerosol can rusts
Context
I was specifying an aerosol cleaner for retail. Forming leaves bare metal exposed on the underside rim of the can.
What happened
Nothing went wrong with mine. I had watched it happen to cans in my own house, shaving cream mostly, where the underside rusts and leaves a ring on whatever it was sitting on. A can that fails that way fails months later, in a customer's hand, long after everyone involved has moved on.
What I changed
I had the line paint the underside along with the body, before the first production run.
Result
Almost nothing per unit and the failure mode is gone. The observation came from cans I had used myself, not from a spec sheet. Most of what I know about how things fail came from using them.