What's this grey stuff on the inside of my keggle?

[btino]

A few years ago I had a friend give me his old keggle he used as a boil kettle that I would like to use as my HLT. It’s been in my attic waiting for me to complete my single tier brew stand (which is now in the kettle/plumbing phase). I have two other keggles that have cleaned up rather nicely with a green scrubber and Bar Keepers Friend.

I can’t seem to figure out what is inside this keg that has all but drained my elbow grease and disintegrated my scrubbing pads. Is this greyish spray paint like coating, beer stone?

I know I also have some work ahead of me knocking off the rusted slag and it looks like somebody tried scrubbing the rust with something more harsh than BKF and scrub pad and made more progress on removing the grey stuff than me.

My biggest concern is off flavors but I’d like it to look somewhat nice without throwing hours of sweat and tears at it.

Ive read so many threads that I’ve stumped myself and would appreciate any advice. Do I use abrasives to polish the entire inside or can I use a cleaner on the grey stuff and sand only the rust spots?

Here’s the Molson keg I am working with, along with a close-up, compared to an AB keg I would like it to match with. (visually of course)

Thanks for any advice on next steps!

 

[fork]

Maybe he bumped it with the grinder when he cut the lid off, or it got heated and discolored from sparks from the grinder when it was being cut. Whatever you do, don't sand it or grind it with something that has been used on non-stainless steel, or it will begin to rust, also, don't use steel wool.

 

[LKHA]

may have boiled a PBW or Oxi clean dont ask. mild scrub down while doing test will have you ready to rock..

 

[btino]

If you look real close at the top picture, you can see that the grey stuff is completely covering the inside of the keg. From the bottom all the way to under the cut top. Almost like a sprayed on coating of some sort.

The actual small areas that look different are what is more "polished" around the the rust spots (highlighted in the middle close up). You can kinda see the swirls made from whatever abrasive they used.

The bottom picture is another keg I have all nice and shiny.

 

[LKHA]

boiled PBW will leave a discolor use a brilo pad and clean it up if worried no problem

 

[day_trippr]

boiled PBW will leave a discolor use a brilo pad and clean it up if worried no problem

Whoa! Ya don't scour stainless with steel wool!

Cheers!

 

[LKHA]

no not steel wool the 3M style brillo pad

 

[BSD_Glass]

It is really had to tell from pictures but it almost looks sand blasted.

Have you gotten ANY of it to scrub off?

Just a guess.

BSD

 

[AndrewD]

Might be mineral build up from boiling hard water repeatedly. Have you tried acid )vinegar) on a test spot?

 

[btino]

I appreciate your comments!!

It's not like a sand blast or pitted. I was thinking the same thing as Andrew. Some sort of build up or beer stone. Which ive never seen either one of so I can only assume.

BKF did a better job than soap and water in making the grey stuff cleaner and taking out some of the rust.

Last night I poured a couple ozs of white wine vinegar in the bottom ring and let it sit in the garage for about 18 hours at 50ish degrees. I just now used one of Kroger's heavy duty green scouring pads rubbing pretty hard for about 30 seconds and cleaned off half that bottom circle (1-2 inches square?). Not sure I'll survive doing the entire inside. Bobby_M's grinder method is looking like an easier option...

I think I remember reading about some vinegar/acid soak at 170+ degrees somewhere in a different thread so I'll do more reading.

 

[Monster Mash]

Acid #5 works wonders for cleaning stainless, you may want to try that. I use it on my boil pot and it gets rid of beer stone without scrubbing.

 

[AndrewD]

Not sure what Acid #5 is like, but some sort of gel or foam acid cleaner might allow you to soak the surface without investing in 15 gallons of cleaner.