Stainless fittings on Aluminum kettle

[stixobutta]

Galvanic Corrosion of my Kettle

I bought a heavy gauge aluminum 40qt pot and also some Stainless 304 weldless fittings ( hop screen, ball valve and thermometer).

I drilled and installed all the fittings and decided to wet test the kettle for a few hours. Ended up not going back to it for almost a day.

I should have known better than to leave it for so long as the next day I found slight pitting of the aluminum at areas where the stainless screen and washers had been in contact while submerged.

The dissimilar metals and water started electrolysis. (slaps forehead) I was surprised that it was that noticeable in such a short time. I've owned boats and also work on naval ships so I have dealt with the very same issues a hundred times before. I should have known better from the start.

This is really is only a problem if you where going to leave water in the kettle for hours on end all the time.

This is just one more thing to consider when equipping your all grain setup.

I don't feel that this is overly detrimental to my brew so long as I am meticulous about my cleaning and drying after each use.

 

[sonex]

I have been working in the metal trades for over 20 years and believe me pitting did not happen in one day from electrolysis. it takes along time to see any damage. the electrical reaction is so minute it usually takes years for damage. more than likely the hard metal of the ss on the soft aluminum scratched or indented the aluminum.

 

[stixobutta]

I would have agreed with you yesterday but the pattern at which the pitting appeared is what confirmed it for me.

The stainless braid I installed is long enough to sit around the inner circumference of the kettle and the pitting (enough to feel with my finger though slight) appeared on the kettle bottom an side exactly in the same shape as the screen. There was definitely no abrasive action from simply laying the screen in place.

I will fill it up again and see if my meter tells me anything.

 

[Golddiggie]

Did you condition the pot before installing the fittings? I did with mine and had no issues at all. It continues to get used by my brew-buddy and it shows no corrosion. It doesn't have a bottom screen in it, but there is a stainless 3 piece ball valve installed. I did place a silicone o-ring on the inside, against the aluminum before the locknut. The outside has another silicone o-ring against the ball valve body. Maybe that's enough of a barrier to not have any reaction. Although the nipple is still going through the wall of the pot.

 

[stixobutta]

I did condition it, and also did a couple of extract brews in it while building my mash tun. And like I said, I have no reason to ever leave water in it except while brewing. Just while checking the fit up did I get distracted.

I cleaned the tiny oxide spots off and will probably never see any more corrosion so long as I don't leave everything submerged for days on end.

This was more of a Hey by the way, don't leave the two metals submerged for extended periods.