How to remove rust from a bad passitivated solder

[copachono]

hi all, well i got a ferrule that its rusting from inside and probably this was non passitivaded after the solder, so im not sure it scrubbing will help out then starsan pure about 1 onz per gallon so i can passitivate this

 

[schmurf]

Make a paste with baking soda and water and rub it on the rusty parts. Usually works well.

 

[copachono]

im gpnna try this one, its gonna be though since its a 1/2" trai clamp, but im gonna try to remove it this way and passitivate

 

[Jayjay1976]

Barkeeper's Friend will remove the rust and passivate at the same time.

 

[LarMoeCur]

If the fitting was soldered in using Silver Solder then is sounds like heat tint. Heat tint is also called bluing but it can be yellow or brown or even rainbow colored depending on the heating process. In a nutshell the stainless was heated to a point which depleted the Chromium Oxide layer. Normally, the Chromium Oxide layer is self healing referred to as Chromium creep by welders. For lack of proper terms the Chromium in the Stainless is being blocked by the heat tint preventing it from creating a new Chromium Oxide layer. It will continue to rust until you strip away the heat tinted area.

Elbow grease and some sort of acid is the fix. I think most home brewers use Bar Keepers Friend which contains Oxalic acid. I would mix it BKF into a thick paste with some water. Then scrub/polish the rusted area. Maybe if you can get a dremel with a small polishing wheel/tip into the affected area. Wear PPE if you use a dremel! You do not want BKF in your eyes. You can also mix baking soda and vinegar into a paste and do the same thing.

Once all the impurities (heat tint layer) has been striped away. A clean layer of Stainless steel will be exposed. Then the Chromium will instantly bond with Oxygen and reform the Chromium Oxide layer which prevents corrosion.

Sorry all that to say scrub the hell out of it with acid. I talk to much.

 

[Golddiggie]

I just passivated the latest sparge arm I got back from the welder (during lunch). Cleaned up a bit with BKF and then put into a pot with some hot citric acid solution (~10% concentration). Had it at a low simmer for 10 minutes, then turned it up for a harder simmer for another five minutes. Does a real nice job of things. Probably not as good as a true passivation process (either electrical or high concentration acid dip) but more than enough for this use.

 

[day_trippr]

Actually 4-10% hot citric acid is one of the preferred methods...

Cheers!

 

[Golddiggie]

Actually 4-10% hot citric acid is one of the preferred methods...

Cheers!

I'm working my way through a 5# bag of citric acid powder. Using it for passivation. I had thought about trying to use some in the wet tumbler (for cases) but didn't end up needing any due to using a different cleaner.

 

[Bobby_M]

hi all, well i got a ferrule that its rusting from inside and probably this was non passitivaded after the solder, so im not sure it scrubbing will help out then starsan pure about 1 onz per gallon so i can passitivate this

If it really is rust, it would more likely be due to not washing the flux off completely. Post a picture of the situation.

 

[copachono]

If the fitting was soldered in using Silver Solder then is sounds like heat tint. Heat tint is also called bluing but it can be yellow or brown or even rainbow colored depending on the heating process. In a nutshell the stainless was heated to a point which depleted the Chromium Oxide layer. Normally, the Chromium Oxide layer is self healing referred to as Chromium creep by welders. For lack of proper terms the Chromium in the Stainless is being blocked by the heat tint preventing it from creating a new Chromium Oxide layer. It will continue to rust until you strip away the heat tinted area.

Elbow grease and some sort of acid is the fix. I think most home brewers use Bar Keepers Friend which contains Oxalic acid. I would mix it BKF into a thick paste with some water. Then scrub/polish the rusted area. Maybe if you can get a dremel with a small polishing wheel/tip into the affected area. Wear PPE if you use a dremel! You do not want BKF in your eyes. You can also mix baking soda and vinegar into a paste and do the same thing.

Once all the impurities (heat tint layer) has been striped away. A clean layer of Stainless steel will be exposed. Then the Chromium will instantly bond with Oxygen and reform the Chromium Oxide layer which prevents corrosion.

Sorry all that to say scrub the hell out of it with acid. I talk to much.

dont worry i know its kinda the thing to do, scruff the hell out of it and passitivate, but scrubbing a 1/2" hole its quite hard, i tried barkeppers friend and baking soda, next comes a paste, its a lemon acid paste i have that its meat to clean SS, its quite strong, the BKF and soda, did romove some of the rust but i can see still some there aound the black mark of the solder.

the fittings are from a pump i bought a chugger pump for backup, so im not in the need of them and they were tig solder, it look like a really good solder but this wasnt cleanned as it should, there are still some blue marks from the exposure on the outside, but the inside look black with rust, i thin the last thing to do would be to machine thi out alittle bit to expose the SS metal then do a full passitivation on the metal, but for the moments im still trying to clean this out

 

[copachono]

If it really is rust, it would more likely be due to not washing the flux off completely. Post a picture of the situation.

that could be the case, but this thing must be really old solder, so i think i have to remove all this layer of oxide and rust before, i was thinkinh also on a pickling solution, when i worked on SS this was wha we used to cleand and passitivate afther soldering, but im no sure on this old solder if it will work

 

[Golddiggie]

TIG doesn't include 'solder' it's welding. Soldering is typically used with things like oxy-acetylene brazing/soldering/welding (welding can be used for all the processes, but soldering and brazing not so much).

IME, it doesn't matter if the fusion is new, or old, provided it was done correctly. Also TIG doesn't use ANY flux for the process. Flux is used when shielding gasses are NOT used.

Get some citric acid, make up a strong solution and let it soak (use hot solution to reduce the time needed). Or make up a thick paste and use that.

IME, if the passivation was done decently, you wouldn't get any 'rust' to return. At this point you need to decide if it's worth trying to fix this or just toss and not worry about it. If it's a 'backup' item, then I really wouldn't spend much time on it. Since you can buy stainless pump heads in either NPT or TC connections easily enough, I wouldn't waste any more time on the problem one. Either toss or take to a local scrap yard and get <$1 for the item.

 

[copachono]

my bad, I totally forgot about it in Spanish welding or soldering its the same word, so that was my mistake, this were welded and the weld were pretty good, and buffer on the outside on the inside it seems that it were machined after the welding so, this may be the proble, but i mage to clean an passivate this pumps heads, first i tried with a Ecolab product called lemon ez, and it clean it fine but there were some mark and some rust on the walls, so i decided to not give up and pick up a pickling gel from my local SS shop, and that made it so clean, the bad thing about it its that i need to buff some parts of the head because they got dull due the strong acid, but so far so good, i will passivate on Citric acid this night

 

[LarMoeCur]

my bad, I totally forgot about it in Spanish welding or soldering its the same word, so that was my mistake, this were welded and the weld were pretty good, and buffer on the outside on the inside it seems that it were machined after the welding so, this may be the proble, but i mage to clean an passivate this pumps heads, first i tried with a Ecolab product called lemon ez, and it clean it fine but there were some mark and some rust on the walls, so i decided to not give up and pick up a pickling gel from my local SS shop, and that made it so clean, the bad thing about it its that i need to buff some parts of the head because they got dull due the strong acid, but so far so good, i will passivate on Citric acid this night

You do not need to passivate it again. The pickling gel you used is most likely Nitric Acid or Hydrofluoric Acid or both of them. Any acid can be used to remove the impurities and free iron on the surface of the stainless caused by the welding process. Once your rinse the acid off. The oxygen in the air bounds with the Chromium in the stainless steel and instantly oxidizes. Putting the stainless steel in a "passive" condition. The pickling gel is more then enough acid to complete the passivating process.

 

[copachono]

This were before, later will post how it went