Stainless Steel Rusting?

[tonydav]

I've got an old SS keg that had a moderate amount of rust and crap on it. Using the angle grinder and stiff brush I cleaned the rust off. Well two weeks later it's getting more rust just sitting in the shed. Before I redo the cleaning I thought I'd check if there's some sort of treatment that stops it rusting after cleaning as I don't want to keep doing the angle grinder thing.

On another note, I have a 22L keg that has stopped pouring (at 90% full). Definitely not a problem with gas, lines etc so all I can think is that a hop pellet(s) has become stuck in the intake tube (it is an American Pale Ale and had a lot of hops in it). Does anyone have any suggestions on how to fix the problem?

thanks,
tony

 

[Aussie Claret]

Don't know about the first problem, but with the second attached a black beer disconnect to your gas supply and blow some CO2 into the keg through the outpost, down the spear which if anything is blocking should remove it.
AC

 

[randyrob]

I've got an old SS keg that had a moderate amount of rust and crap on it. Using the angle grinder and stiff brush I cleaned the rust off. Well two weeks later it's getting more rust just sitting in the shed. Before I redo the cleaning I thought I'd check if there's some sort of treatment that stops it rusting after cleaning as I don't want to keep doing the angle grinder thing.

On another note, I have a 22L keg that has stopped pouring (at 90% full). Definitely not a problem with gas, lines etc so all I can think is that a hop pellet(s) has become stuck in the intake tube (it is an American Pale Ale and had a lot of hops in it). Does anyone have any suggestions on how to fix the problem?

thanks,
tony

Heya,

was the angle grinder brush made of ss or another form of metal because it will inbed that metal into the
keg and cause it to rust more.

if the keg is blocked you could try attaching the gas line to the 'beer out' and give it a squirt?
just an idea

Rob.

 

[Adamt]

Stainless steel will rust if you scratch the outer coating. There's some treatment information somewhere on the forums (cant remember what it was) that helps restore stainless steel's protective layer.

As far as teh stuck keg... maybe attach your gas line to your liquid post (with your liquid disconnect) and give it a short blast? Make sure you have a check valve installed before doing this.

 

[devo]

It's the brush fibres that you have inbedded into the stainless steel that are most likely causing the rust to spots not the SS itself.

 

[TidalPete]

Stainless steel will rust if you scratch the outer coating. There's some treatment information somewhere on the forums (cant remember what it was) that helps restore stainless steel's protective layer.

Nitric acid is the thing for treating stainless steel to prevent rust spot, etc.

:beer:

 

[tonydav]

Good answers thanks guys. I'll try the gas thing - have to change a disco first.

Any ideas where to get nitric acid?

tony

 

[Keifer]

I made the mistake of using an angle grinder on my ss and it started to rust everywhere. I just scrubbed it with a scourer pad, each time less rust showed up. 3 goes later theres very little rust left. Remember if you scratch the surface, make sure it dries up for a while so the protective layer can reform.

 

[Finite]

I made the mistake of using an angle grinder on my ss and it started to rust everywhere. I just scrubbed it with a scourer pad, each time less rust showed up. 3 goes later theres very little rust left. Remember if you scratch the surface, make sure it dries up for a while so the protective layer can reform.

I had a similar experiance. I used an angle grinder to cut the tops off all my kegs and the tiny sparks can while hot stick to the sides and bottom of the keg and cause little rust spots. After I cut each one I always rinse very well then scrub with a scourer to get all the marks off. I then let it drain upside down and dry over night. I also treat any grinded or filed edges with some course sandpaper then a finer grade.

I used the same method of starting at a course grade sandpaper and working to a finer one for the outside of my keg. It came up very shiny and hasnt had a speck of rust since.

I posted the process here: http://www.aussiehomebrewer.com/forum/inde...c=13099&hl=

 

[Dan`]

stainless dosent have a protective layer. i think you might be thinking of alloy or something there, but anyway

if any sanding/grinding equipment is used for stainless it will implant small ammounts of what ever its been used on before. so if you use a grinding wheel that you have cut mild steel with before, or a sanding disc you will implant steel onto the surface of the stainless and then obviously it will rust. keep all the stuff you use on your shinny stinless only for your stainless. then you wont get any problems.

ive been working with stainless for ages, but theres nothing worse than making something, then a week later realising you reused a sanding belt that was previously used for mild... :wacko:

 

[Adamt]

stainless dosent have a protective layer. i think you might be thinking of alloy or something there, but anyway

Sorry, completely and utterly false. Besides, stainless steel IS an alloy. Stainless steel is teh generic term for a steel alloy containing at least 10% Chromium. The Chromium forms a Chromium Oxide layer on the outside of the metal which is effectively inert against corrosion. As I said earlier in the thread once this layer is broken corrosion can occur very quickly. The Chromium Oxide layer will return over time, its quickness depending on the atmosphere (absence of Oxygen prevents this) and the stainless steel composition (of Chromium and other metals such as Nickel, Titanium, Molybdenum and Niobium).

...this thread was dead anyway!

 

[domonsura]

Sorry, completely and utterly false. Besides, stainless steel IS an alloy. Stainless steel is teh generic term for a steel alloy containing at least 10% Chromium. The Chromium forms a Chromium Oxide layer on the outside of the metal which is effectively inert against corrosion. As I said earlier in the thread once this layer is broken corrosion can occur very quickly. The Chromium Oxide layer will return over time, its quickness depending on the atmosphere (absence of Oxygen prevents this) and the stainless steel composition (of Chromium and other metals such as Nickel, Titanium, Molybdenum and Niobium).

...this thread was dead anyway!

Absolutely right AdamT.

 

[chillamacgilla73]

Good answers thanks guys. I'll try the gas thing - have to change a disco first.

Any ideas where to get nitric acid?

tony

Tony - you won't be able to buy nitric acid(Pickling/passivating paste) as it is extremely dangerous and corrosive and I believe in WA it is only sold under licence with traceability. A scourer and abrasive creme cleaner(Jif, Gumption etc) will remove the rusty layer but it is a PITA. Stainless fab shops use scourer discs fitted to grinders but I believe they are well pricey. Ring a few sheetmetal fabricators and see if they can help you out. It's amazing what will get done for a few king browns.

Cheers

 

[Sammus]

I can walk in and buy pickling paste from BOC. I wouldnt use the stuff though after reading about the hydroflouric acid in it (try a search on wiki...)

if you grind only use proper SS grinding discs, if you get little ferrous bits inpregnated in the stainless itll rust a lot.

The best cheapest ways to repassivate (the protective layer on stainless) is to go and buy some oxalic acid from bunnings or something (sold as paint remover), scrub it with a green scrubby, let it sit for 10 mins, do it again, then rinse thoroughly and dry. according to palmer you should let it sit for a few days or a week to completely repassivate.

Ive also succesfully used citric acid from the supermarket (sold as crystals, make up as stong a solutions as you can - its not very soluble). Citric takes a lot longer though.

 

[bigfridge]

The best cheapest ways to repassivate (the protective layer on stainless) is to go and buy some oxalic acid from bunnings or something (sold as paint remover), scrub it with a green scrubby, let it sit for 10 mins, do it again, then rinse thoroughly and dry. according to palmer you should let it sit for a few days or a week to completely repassivate.

Guys,

We aren't building space rockets or components for nuclear power stations here - just brew pots.

The cheapest way is just to grind with a wheel/disc that has not been used on mild steel, wash with your favourite cleaner/detergent, rinse and leave for a day or two. The oxide layer forms real fast - which is why stainless is a buggar to solder (need a corrosive flux to remove the rapidly re-forming oxide layer).

John Palmer originally maintained that the layer took weeks to form but during a private conversation I was alble to show that this was a bit conservative - hence the few days that he now advocates.

It really is a simple, chemical free process.

David

Metallurgist with 8 years experience in a steelworks producing stainless steel castings, forgings and bars.