Another keggle rust thread.

[BargainFittings]

You can repassivate with citric and ascorbic acid in hot water like we do for SS repassivation after welding or grinding and breaking the surface passivation. A 50-50 mix of 1 Lb acid blend in 4gallons of water, heated to 180 degrees, and left to cool for about 6-8 hours will extract the soluble iron and rebuild the oxides to protect the stainless steel where it has been heat affected. This is slower than the nitric acid method but safely do able by the homebrewer, and is the method of choice in the food and beverage handling industry these days. You will only need to cover the weld area, not fill entire keg as only weld or grinding/ polishing area needs attention.

Can the mix be moved to another keg afterwards and used again?

 

[o2nut]

I think the acid mix is your best bet. It will actually repassivate the stainless. I don't thing BKF will actually repassivate it but instead just polish/clean it. Sounds like kludue has a lot of experience with it. I recommissioned a stainless 55 gallon drum once. I had to remove the top and bottom because they were folded over seams and re welded them. I searched in vain trying to find a way to repassivate the tank and welds. One day when I way in HD I was looking at some of the concrete etchers and cleaners when I found one that had nitric and citric acid blend. I ended up dilluting that with water and have never had a rust issue. I can't say it was FDA approved but I use the drum for a fermentation tank for wine and I am still normal (physically that is, mentally I've always had issues).
I work in the welding field so the last option is a product from a company called Harris Welco, every welding supply house will know who this is. It is a compound called 302. I could only find the MSDS sheet on their website. But this is nasty stuff that really works. Prob no one will stock this and the shipping is a pain because it is a corrosive, but this will do the trick.
Hope some of this helps.


http://www.harrisproductsgroup.com/pdf/MSDS/Compound_302.pdf

 

[kladue]

The acid blend should handle more than one keg application, the key to getting durations worked out would be get the solution hot (180 Max) and let it cool back to ambient temperature which will give the iron extraction time to complete. The common industry method used to determine when passivation is done is to monitor iron level in solution, when it plateaus the passivation is usually complete. Having worked with and tormented the folks from Astro Pak with questions about the process, it looks like the acid blend is the easiest and safest way for the home brewing community to repassivate the kegs and plumbing on their rigs.

 

[tasq]

The acid blend should handle more than one keg application, the key to getting durations worked out would be get the solution hot (180 Max) and let it cool back to ambient temperature which will give the iron extraction time to complete. The common industry method used to determine when passivation is done is to monitor iron level in solution, when it plateaus the passivation is usually complete. Having worked with and tormented the folks from Astro Pak with questions about the process, it looks like the acid blend is the easiest and safest way for the home brewing community to repassivate the kegs and plumbing on their rigs.

Where does one acquire the acids?

Thanks!

 

[Berniep]

Where does one acquire the acids?

Thanks!

I looked for something at home improvement stores with nitric acid in it but never found anything. Ended up buying a squirt bottle of citric acid gel made for passivation from someone online. I need some more but I might just have to use the citric acid vitamin c recipe. Should be able to get it at health food stores. Seems like i remember the squirt bottle stuff was pretty expensive.

 

[kladue]

You can find both in powder form on Amazon, or in health food and craft stores, finding Nitric acid is going to be difficult if not impossible for the average person. Leave the Nitric acid to the professionals and go with the citric/ascorbic acid method, a bit slower but safe.

 

[doctorsbro]

what stainless wire did he use? My guess he used the wrong wire, remember some stainless steels still rust, just not as fast, if it was migged then it needs to be a 308 wire with 98% argon and 2% co2. My guess is that judging by the picture, that was mig welded and he just spot welded around the fitting, if thats a tig weld it looks like it was his first time picking up a tig torch. Also, some people when tig welding lay down the weld with filler rod and then go back over the weld to "polish" it and make the weld look better which can cause the weld to rust

I cant believe so many people have problems with stainless rusting.... ive tig'd, mig'd, and stick welded stainless and have never had any weld rust, i think peoples main problems are poor welding/fabrication methods, improper materials, shielding gas, etc... and also contamination of the stainless from using the wrong grinding disks, wire brushes, etc, even drill bits can cause stainless to rust .

 

[Spyksman]

I would use 316 it dosent hurt to step up. We used 316 on any type of vessle repair and even when constructing them. I used to work for Delmonte. you can use Muratic acid "swimming pool acid" just be carefull with the fumes. we used it often to clean up welds. They wanted us to delute it but i would use it straight it works faster and it eats up contanimates "iron of carbon" Some times when welding the cheaper stainless the small amount of carbon would come to the top that is why we used the 316 we used it when mig and tig as well and some times when arc welding as well. Man they hated to buy the 316
Cheap A$$es but they wanted quality.we also used the muratic acid to clean the stainless where some one drug a piece of black iron over it because that would always rust. The other thing you can do is use a new grinding wheel or pad to take it off and then use the acid again. Hope this helps.

 

[doctorsbro]

i was thinking that as well, some stianless's are poorly made, 316 has a much higher content of chromium which means it has even less iron in it. If any of you are buying stainless, get the heat number and manufacturer of the material and find out the parameters.....

 

[tasq]

Wow... bringing this thread back from the dead, eh?. I ended up replacing these kegs and had a REAL welder do the job. I'm much happier with my rig now.

 

[CrowbarKarl]

You can repassivate with citric and ascorbic acid in hot water like we do for SS repassivation after welding or grinding and breaking the surface passivation. A 50-50 mix of 1 Lb acid blend in 4gallons of water, heated to 180 degrees, and left to cool for about 6-8 hours will extract the soluble iron and rebuild the oxides to protect the stainless steel where it has been heat affected. This is slower than the nitric acid method but safely do able by the homebrewer, and is the method of choice in the food and beverage handling industry these days. You will only need to cover the weld area, not fill entire keg as only weld or grinding/ polishing area needs attention.

Not to wake a thread from the dead, but it is ok to leave copper and brass parts such as a copper diptube and brass nut while repassivation of the keg? My HERMS also has a copper coil in the HLT and didn't know if that needed to be removed as well.
Cheers!

 

[theQ]

You can repassivate with citric and ascorbic acid in hot water like we do for SS repassivation after welding or grinding and breaking the surface passivation. A 50-50 mix of 1 Lb acid blend in 4gallons of water, heated to 180 degrees, and left to cool for about 6-8 hours will extract the soluble iron and rebuild the oxides to protect the stainless steel where it has been heat affected. This is slower than the nitric acid method but safely do able by the homebrewer, and is the method of choice in the food and beverage handling industry these days. You will only need to cover the weld area, not fill entire keg as only weld or grinding/ polishing area needs attention.

Starsan is an acid, will that work as well ?

 

[acidrain]

Not to wake a thread from the dead, but it is ok to leave copper and brass parts such as a copper diptube and brass nut while repassivation of the keg? My HERMS also has a copper coil in the HLT and didn't know if that needed to be removed as well.
Cheers!

Probably OK, but when in doubt, I would remove them.

Starsan is an acid, will that work as well ?

No