Keg passivation problems

[DarkHobo]

Hey, so we were passivating some kegs but we ran into some problems during the rinse. Our passivated kegs would not go above 5.5-6 ph no matter how much we rinsed. The first set we tried we did cold water first around 7 1 minute, 10 30 second, and 10 10 second rinses. We then tried hot water and rinsed for 5 1 minute, 5 30 second, and a few 10 second rinses. Then we swapped back to cold water because the hot water wasn't making a difference and did a bunch more. We tested the pH after every rinse. Many ph strips hit the trash this day.

Eventually we just sanitized about half of them and did 2 30 second rinses first to get the pH to the same level, 5.5-6.

I have three questions. Is there any problems, health or flavor wise, with filling those kegs with beer as is? Should we neutralize the kegs with a mild caustic? Or is there something we are missing?

 

[zachattack]

Some tap water comes out at pH 6.

 

[DarkHobo]

True, but ours is 7.5-8 and we tested the water out of the tap. Out of our first water pipe and into the keg. They all came out at 7.5ish

 

[DarkHobo]

I am just interested in whether the pH indicates there is enough acid mix left to alter flavor or ,however unlikely, pose a health risk.

 

[gnef]

If all you are concerned about is the residual acid, I would just pour in some baking soda, add some water, and slosh it around, then rinse it out, add fresh water, and check the pH, repeat if needed.

 

[DarkHobo]

That's what I was thinking. But at this point the sanitized all the kegs as is. So the question that remains is, will it affect the flavor or cause health issues? I kind of doubt it besides maybe just making the beer ever so slightly more tart. But, since many places have water at 6 ph I really don't think the concentration is enough to make a detectable difference.

EDIT: My worry about the flavor and the health part stem from a worry about residue. I am thinking that maybe the reason the pH won't go up is that there is a residue built up on the walls of the keg. And if we fill them with beer and let them sit they will dissolve more of the acids than the water could. I am thinking, if they will let me, to fill a keg with beer/water and let it sit for a few days then check the pH and compare it to the initial pH.

 

[day_trippr]

After all this does it really make sense that there could be enough "residue" to significantly shift the ph of rinse water?

Something ain't right...

Cheers!

 

[DarkHobo]

That is what I was thinking. There shouldn't have been enough "residue" to shift the pH of that sheer amount of water.

EDIT: I have been doing a lot of research into this now and everything I have been reading says you shouldn't need to neutralize the acid and a rinse should work fine. Why the heck is our rinse not working then?

One place did recommend a caustic rinse after the passivation but that was for "Free-machining grade stainless" which were listed as some 400 series alloys. But the 300 series only needs caustic cycle, passivation, and then rinse/sanitation. Or at least it should.