Cathodic Protection For Aluminium Kettle

[aaronpetersen]

I have recently installed an electric element (like this) into my aluminium kettle. I brewed with it for the first time on the weekend and it now has very obvious pitting, which never occurred when I used a gas burner. I've done a little reading about ways to prevent pitting and according to this source, connecting the kettle to the negative pole of a DC source will solve the problem. I'm therefore planning to attach the kettle to a 12V battery with a length of copper wire clamped to the kettle handle.
Has anyone tried doing that? Did it work? Any other methods people have successfully used to prevent pitting? I could use a sacrificial anode made of magnesium but the battery method sounds easier to me.
If your recommendation is to get a stainless kettle then keep it to yourself
I will mention that my kettle has a stainless ball valve if that makes any difference.

 

[insane_rosenberg]

G'Day Aaron,

That's a strange one mate. I read through your links (the element one needs repair), and as an electronic engineer, I think you'll really have to look into that battery thing a bit further.
Simply linking the negative pole of a battery to the pot will not do anything if the positive pole is just floating.

If you're sure you're seeing galvanic corrosion (the description does seem to fit), you might have more luck with the insulation method. If there is no metallic contact between your stainless (tap and element) and your aluminum then galvanic corrosion cannot occur.

Sorry I don't actually have any experience with your problem, just looking at it from a scientific standpoint.

 

[Bongchitis]

Have you used any caustic cleaning solutions on your pot? Caustic and aluminium are not friends.

As shane says there really shouldn't be an issue if there is no contact of dis-similiar metals so if you have them insulated then all should be sweet. That kind/degree of corrosion does not happen without unfavourable environment and I would check everything about your element installation. If it has pitted that much after 1 brew then you are getting alzhiemers early and your kettle will be useless in the not too distant future.

My reccomendation is to get a stainless kettle h34r:

 

[aaronpetersen]

Thanks guys. From what I have read, it seems that water high in chlorides can also cause galvanic corrosion on aluminium. I always add CaCl2 to my brew water so it could be that causing the corrosion and not the stainless valve. Having said that, why then didn't I get pitting before I installed the electric element? Maybe it is the stainless causing the corrosion and adding an extra lump of stainless (the new electric element) has just sped the process up?
With regard to insulating the ball valve from the kettle, doesn't the wort act as a fairly effective conductor thus making it impossible to do that, even if there is no physical contact?

Edit: I've only ever cleaned the kettle with water, no caustics.

 

[Bongchitis]

It would seem then something surrounding the installation of the element is to blame if nothing else has changed. If it was due to just contact with dis-similar metal it would be localised corrosion but if the pitting is everywhere that the water was I am guessing some kind of cell has been set up and somehow your element is to blame. Have you checked for earth leakage? Is the element touching the kettle? Is there any way that the kettle has become part of the circuit? Other than that I really don't know.

 

[kjparker]

The element would be electrically touching, as the backing nut would be against the walls of the kettle.

You could possibly put a fiber washer in between to insulate it, and make sure that the threads of the element do not touch the kettle, completely isolating the element.

doing this however would leave the kettle unearthed in the event of a fault.... Probably not a good idea..

 

[insane_rosenberg]

With regard to insulating the ball valve from the kettle, doesn't the wort act as a fairly effective conductor thus making it impossible to do that, even if there is no physical contact?

Without going into the full details (ions and such), Galvanic Corrosion occurs when there is a closed circuit, one half being the path through the metal, and the other being the path through the liquid. If you insulate between your two metals, you break the circuit. No more galvanic corrosion.

 

[kevo]

Had to do a double take - thought this was Catholic protection for an aluminium kettle.

What would Jesus brew?

 

[razz]

Had to do a double take - thought this was Catholic protection for an aluminium kettle.

What would Jesus brew?

Wine?

 

[the_new_darren]

Wine?

Nah Hebrews