Rust(?) Spots in new Keggle

[stratslinger]

I'm in the process of setting up a new keggle and HLT, hoping to brew with both next weekend, and yesterday I noticed what appear to be a handful of rust spots in the bottom of the keggle.

Now, these could be beer stone - I've never seen the stuff before, so I'll admit I could be mistaking the one for the other. So, a picture to help identify:

What's the best way to handle this? I do not have an angle grinder, but I do have a few different drills and such, and plenty of elbow grease to apply.

 

[janivar123]

Do not try to grind away the rust, it will just get worse fast

Hydrocloric azid and a kitchen scrubby/sponge thingy
You will need chemical gloves and need to work outside
Rinse well and set to dry

I hear barkeepers friend work too

 

[Brew-ta-sauraus]

Barkeepers friend is what I used for same issue. Store your keggle dry going forward and you won't have a problem.

 

[dutchoven]

Beer stone, at least what I saw in my kegs after cutting them open, is a hard, light-colored, almost chalky surface coating.

How did you cut your lid? Plasma torch? Those spots almost look like slag marks on the bottom?

Bar Keeper's friend should take care of it. I wouldn't recommend using hydrochloric acid ... it will further deteriorate the passive layer on the stainless, making the rust worse.

 

[stratslinger]

Yeah, had it cut with a plasma cutter... If they're slag spots, any differences in how I deal with them?

Thanks for the advice so far!

 

[OneHoppyGuy]

Beerstone (Calcium oxalate, as 'beerstone', is a brownish precipitate that tends to accumulate within vats, barrels and other containers used in the brewing of beer. If not completely removed in a cleaning process, beerstone will leave an unsanitary surface that can harbour microorganisms.[1] Beerstone is composed of calcium and magnesium salts and various organic compounds left over from the brewing process; it promotes the growth of unwanted microorganisms that can adversely affect or even ruin the flavor of a batch of beer.) does not occur until you have actually used the kettle.

When the keggle was cut hot slag landed in those spots forcing the chromium in the steel away from the surface. The surface must be repassivated. An acid is required to draw the chromium back to the surface. The method janivar123 mentioned will work fine. When welding stainless we use Star San concentrate (machine shops use nitric acid).

 

[stratslinger]

So, if I'm getting this right, I need to use some sort of acid solution (sounds like a higher concentration of starsan - what concentration would be good here? 1oz:1gallon? more/less?) and a SS scrubby to get rid of the rust and re-passivate the stainless. And then maybe hit the whole thing with a good scrub down with bar keeper's friend for good measure?

And if the starsan solution won't do it and I need to use something stronger, where would I go to acquire it? What exactlty would I look for?

 

[janivar123]

Im guessing consentrate mean undiluted star-san
I wouldnt use a metal scrubby, kitchen sponge with the green scrubby surface should be plenty

 

[OneHoppyGuy]

a few drops of Star San on the keggle bottom and a plastic scrubby... then clean up with Barkeepers Friend

 

[lpdjshaw]

So, if I'm getting this right, I need to use some sort of acid solution (sounds like a higher concentration of starsan - what concentration would be good here? 1oz:1gallon? more/less?) and a SS scrubby to get rid of the rust and re-passivate the stainless. And then maybe hit the whole thing with a good scrub down with bar keeper's friend for good measure?

And if the starsan solution won't do it and I need to use something stronger, where would I go to acquire it? What exactlty would I look for?

All you need is Bar Keepers Friend and a sponge. Don't use too much water - you want it to be like a thin paste.

 

[stratslinger]

Well, early results in, and as usual, HBT folks rock!

I used a scotch brite pad and bar keeper's friend in a thin paste as described, and the rust is gone. I also used the same to clean out the HLT (no rust, but it just still looked a little dingy), and now both kegs look nice and clean.

You can definitely see on the kettle that those rust spots are absolutely slag - the little bits are still there now. I'm thinking I'm not concerned, since everything in there will be boiled, and I'll be chilling using a CFC, so nothing inside the keggle should ever fall below pasteurization temps.

I'm going to give this a few days, maybe a brew or two, before I call it an official win, which is why I haven't yet posted an official "after" picture.

One thing still bugs me a little bit - if the bar keeper's friend is supposed to be helping to repassivate the stainless steel, should I have left it in contact with the steel for some amount of time before rinsing everything, or is just a good scubbing and subsequent rinse enough? I probably spent 5-10 minutes scrubbing the whole thing out, bottom to top, so the bottom (where the worst of the slag/rust was) was in contact with the bkf paste for 5+ minutes...

 

[stratslinger]

Ugh... So, first attempt turned out not so great.

I still had three or four sizeable slag "nuggets" stuck to the bottom of the keggle that I just couldn't get loose, and those continued to rust despite repeated treatments with bkf. I wracked my brains over what to do about them. Since I have no angle grinder, a stainless steel wire wheel or flapper are kind of out of the question, and I certainly didn't want to take any chisels or anything similar to the keggle and risk embedding other rust inducing metals into the keg.

Then a momentary flash of brilliance came upon me (well, I hope it was brilliant, anyway): I still have my SS keg spear! I used that as a scraper and scraped away the slag spots, then I used some clean 220 grit sandpaper to sand down any scrape marks, hopefully removing anything that was still embedded in the surface of the keggle. The again, I mixed up some BKF paste and coated the bottom of the keggle and left it overnight. It's currently sitting in a couple gallons of water (I had to take apart a couple fittings - I discovered another bit of slag I hadn't noticed earlier directly under the bulkhead!) re-testing for leaks, and when I empty it tonight I'll let it air dry and check in the morning again for any signs of rust. With luck, this thing will finally be good to go - with little time to spare, since it's innagural brew is on Saturday!

 

[ghart999]

so any news on this???

 

[stratslinger]

Well, the bottom's looking good.

That said, there seem to be possible signs of slag splatter (is that really possible?) on the sides of the keg now...

Once re-assembled, all the fittings definitely held leak free, and the bottom air dried rust free, but there appeared to be some thin rust like spots of rust forming along the sides now. But those wiped away, so I'm not altogether convinced that they weren't just some residue.

Gonna give this thing one more good wipe down with a wet cloth tonight to make sure that all the BKF residue is gone (and do the same for the HLT), and tomorrow it's off to the races. If the rust/residue/whatever along the insides returns, I'll be looking into some sort of fine grit sanding pads or sponges that I can put on my random orbit sander and see if that can't knock the remainder of the crap out of there.

 

[ghart999]

That's really strange. I mean I have never even washed mine down after cleaning and its never seen the slightest sign of rust even if what sits in it for days.

 

[stratslinger]

But was yours cut with a plasma cutter? Mine was, and I think that's what's getting me - I think it's the residue from the plasma cutter. The problems on the bottom were definitely due to a couple of grains of plasma cutter slag, and I'm assuming that what I saw on the inside was either more of the same, or just dried BKF paste residue with some more muck mixed in (which would be the best case scenario - meaning I have no further problem!).

Once I give it one last good rinse and wipedown, then brew with it once or twice, I should know for sure. I'm certainly wishing I had thought to ask the guy to fill the kegs up with water before he ever lit up his cutter though...

 

[ghart999]

But the rust on the sides should not have anything to do with plasma slag? That's more of what's getting me.

 

[stratslinger]

I see what you're saying... If it's not just BKF schmegma that wipes away cleanly, I'll get a pic and post it.

 

[stratslinger]

Well, first brew day with the new kegs was a success!

However, during cleanup, I'm fairly sure I spotted signs of the rust-like substance on the side walls of both kegs. And of course, in the midst of cleanup, I failed to snap pictures of either one of them. I'll try to grab those tonight, see what folks think.

 

[Homercidal]

I had enough forewarning when I cut mine to know to fill the keg with water before I started cutting. This caught all of the sparks and globs (well, almost all, I'm sure) in the water and cooled them before they could stick to the inside of the keg.

I still had to do a bit of scrubbing when I got them home, but it was mostly some hazy smoky residue and it cleaned up very well.

 

[stratslinger]

OK, here are the long awaited pictures. After re-examining everything, it turns out that my HLT actually looks considerably worse off than my BK, which is the exact opposite of what I had thought I was dealing with.

Anyway, the HLT:

And a close-up of one of the sides walls:

And now the BK:

And again, close up:

This sure looks like rust to me, but maybe someone can put my fears to rest. And the HLT definitely looks worse off.

Assuming this IS rust, can I just use a fine grit sanding sponge (say a 160 or 220) and go to town on these things by hand, or am I just asking for major hand cramps? Is there any chance I can get my random orbit sander in there, or am I looking to borrow/rent/purchase a grinder and flapper wheel? Obviously I'd have treat everything with BKF again after whatever abrasive treatment is done...

 

[janivar123]

Well if all that is rust your best bet is azid cleaning
A sponge or a syntetic cloth and hydrocloric azid 30%, and it should wipe right off

A minimum of protection is good gloves and goggles

Oh and remove all fittings first sinse there not easy to rinse clean

 

[audger]

you shouldnt suggest using such agressive acids to people who may not know the correct way to use them. that is a good way to get people hurt or at very least make the kettle even worse.

OP- if you arent up on your ASTM standards (ASTM A967 specifically), you should get a new green scrubby sponge, make a thick paste out of barkeepers friend and some water, (adding some lemon juice or vinegar works too), and scrub the hell out of the insides.

the goal here is to create a passive layer of chrome oxide on the surface of the steel. stainless steel contains a few % chromium in the mix, and you need to use an acid in the presence of oxygen to draw out some of that chromium to the surface of the metal and oxidze it to form the passive layer (barkeepers friend = oxacilic acid, which is both an acid and contains oxygen for the chromium to combine with). if you use a very strong acid incorrectly, you can not only strip off the passive layer already on most of the surface, but you can deplete the chromium content of the metal and then you will never again be able to form a passive layer.

yes you can also do this with hydrochloric acid (also called muriatic acid, sold as floor etching chemical at home depot), but you can also make things worse if you use a concentrated acid incorrectly. barkeepers friend is not harsh enough to cause problems even if its misused.

you may not get 100% of the rust off with BKF if there is heavy pitting, but even if there are some small dark spots left over, they should be dark grey instead of brown/rust colored, and they will not continue to rust any further and are harmless.

 

[stratslinger]

Thanks for the attempt audger... But I've done exactly what you describe with the Bar Keeper's Friend a couple times now, and I'm still left with the pictures you see.

I'm not comfortable using HCl, wouldn't know where to pick it up anyway, and I'm not going to attempt it. Someone earlier in the thread suggested using undiluted starsan as an alternative to HCl - just a little on a scotchbrite pad or a green scrubby. Would that also serve to take out the rust and repassivate the stainless? Or maybe that in conjunction with a good treatment of BKF?

 

[stratslinger]

OK... For anyone still reading along: apparently, a scotchbrite pad and undiluted starsan will indeed take this sort of rust right off of a keg. Not sure how long I should have left it exposed to build up a good passive layer - I left it for a couple hours anyway before thoroughly rinsing everything off.

I've now rinsed and dried everything, and it looks squeaky clean. We'll see in a day or two if it remains so.

 

[OneHoppyGuy]

Yay!!

 

[Kaleco]

OP - Update?

 

[stratslinger]

I'll try to remember to double-check them again tonight, now that a few more weeks have gone by with both kegs untouched. But last I had looked at them, both had been treated with undiluted starsan. The starsan removed all signs of rust from both kegs. I treated the HLT, which was definitely in rougher shape than the BK, first, and that one showed no signs of further rust a week or two after being treated. I gave the same treatment to the BK and knocked off all remaining signs of rust there as well. I haven't looked at either of the kegs in a couple weeks, so I'll go and check on them both tonight, and maybe even post a couple pics.

 

[stratslinger]

Sorry for being so delinquent in getting back to this post - I hadn't realized a full 2 weeks had slipped by...

Anyway - I not only checked out both kegs over the weekend, but I brewed with them. I didn't take pictures, but I am happy to report that there is no new sign of rust on either of them. The star san treatment worked flawlessly!

Thanks again folks!