This was touched on in another thread, but I didn't want to hijack, so I'll begin anew.
Here's picks of my freeze plug I had replaced about 2 weeks ago:
Notice that there's no visible outer wear when you look at it. I figured this was due to some sort of coating, possibly zinc plating as otherwise I would expect it to be green if it were copper or brass, or rusty if it were steel. I elected to let the shop replace it as it was directly behind an engine mount and I didn't wanna mess with pulling that.
Here's what it looked like on the inside:
Note the heavy corroded wear at the bottom of the plug. Basically, the plug corroded from the inside out. I know it's probably hard to see, but underneath some of that caked on antifreeze, the plug looks exactly like the outer side. It's just the bottom edge that corroded, which leads me to my question:
What are these things made out of? I'm curious because the the mechanic said it was due to electrolysis, but I'm curious as to what exactly am I "electrolysizing"? Why would I be creating an electrical current in my A/F? Do I have a bad ground somewhere? Am I going to have all my other freeze plugs blow out on me?
I'm really hoping that the plug was plated and accidentally scored upon installation and eventually failed by corrosion due to compromised plating.