Almost empty keg has a harsh metallic taste at first

I'm at the bottom of my first kegged homebrew. When I poured a glass last night it seemed to have a bit of a harsh/metallic taste at first. As the beer warmed up a bit that seemed to dissipate and the beer tasted more as I expected. So being new to kegging I figure this is due to three possible things (or combination of them) and was looking for some help

1. Is this what I've seen referred to as "carbonic bite"? The carbonation level in the beer doesn't seem too high. My serving pressure is around 9-10 psi at the moment.

2. Is my fridge/beer temp too cold? My keggerator is in my garage and it's getting a little cooler here, so I've found my fridge temp is drifting towards 36ish rather than the 40 it was at earlier this month.

3. I think this is the least likely, but what are the possibilities for picking something up from the keg itself? It seemed nice and shiny inside when I bought it, and I have it a good pbw wash inside and on all the fittings prior to the sani and racking.

Thanks!

Bump.

I brewed a Sierra Nevada extract clone that tasted amazing after carbing one week in my keg. Slowly the metallic taste has increased and is now undrinkable.

I purged the keg with co2 before racking, dry hopped in primary and cold crashed. This is a new keg, previously soda but I cleaned well with pbw.

Steel tank rusting inside, maybe?
Or maybe just the apocryphal tank of "bad CO2"?

Might try carbing up a gallon of spring water in a cleaned and sanitized keg to see if that picks up the same metallic note...

Cheers!

I bet it's over carbonated due to the low temp. The difference between proper pressure at 33 degrees and 40 degrees is 3psi. I had similar when I took a keg and my CO2 to a friends place for a weekend gathering. My regulator was set at 14 psi for my 45 degree kegerator. His freezer was set about 36 for lagering. First night it was fine, but the following day degraded with a chewing on tin foil taste.

Just lowering the pressure and purging won't eliminate it immediately. It'll take some time for the solution to find a new equilibrium. After a few days back home, my partial kegs were back to normal. Sloshing around and warming up on the 7 hour drive home probably helped accelerate that in my case.

Well my temp is set to 34 degrees, and regulator was set to 14 psi. I poured a pint and let it sit in the fridge till it was flat - same bitter aftertaste/finish. Good aroma through.

Psi adjusted to 9psi, so I'll let them sit for a few days. I'm swapping gas tanks of that doesn't do it.

My understanding is that carbonic acid is created. Just letting it go flat will release the CO2 which in solution, but it doesn't cause the acid to break down. That takes time.

I would have reduced pressure even further, thinking that a bigger change might help drive the reaction faster. Probably worth some Google time to see what drives the reaction. Letting them warm up might be more effective.

I target 2 volumes as my normal level. I now have a freezer (future keezer) for carbonating and keeping the reserves chilled. It's 39 degrees and pressure is set to 7psi. At 34 degrees it would only need 5 psi.

Any change?

I just checked and it does seem a bit better. I lowered the pressure to 9psi and bumped it up a few degrees. I'll check back in a few days.

I don't want to jump to conclusions, but I might have solved the issue. Last night I moved the temp controller probe from the corner of the freezer to actually taped onto a keg.

It might just be a Monday and I NEEDED a beer, but this Harpoon IPA clone was borderline undrinkable yesterday ( I love 100+ IBU beers but this was too bitter). Today it's a pint I'd pay $6 for...

I've seen folks with the temp probe submersed in water inside the freezer. Mine is just dangling in the air. I should check the surface temp of a keg to see how different it is. In my basement with rare opening of the freezer, it barely ever runs though. So except for initial chilling, I imagine it's uniform with the set point.