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Old 04-12-2010, 04:28 PM   #1
shushikiary
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Default electric heating element rust prevention

Hi all, so I've been doing some reading about using eletric heating elements in SS kegs and ran into people talking about the mild steel face plate of the heating element rusting due to galvanic cathode reactions (like those in hot water heaters, go figure, lol).

I saw that some people put JB weld on the surface, one suggested POR-15 (http://www.por15.com/POR-15/productinfo/1GB/), and some have suggested a sacraficial anode such as an aluminum block or magnesium fire starter.

So I have a few questions about this. First off, if you put JB weld or POR-15 on just the face plate, wont you still get rust on the threads the water has access to inside the nut that holds the element on? Then if you do put it on the threads, you'll have to do it at the time of insersion in which it now becomes a fairly permanent installation (maybe get it out with a breaker bar? haha). I dont like the idea of it being permanent. But what if I plastered the thing in teflon tape to protect the threads?

I dont like the idea of sacraficial anodes because I'm worried about the added magnesium or aluminum ions floating around in the water/wort that might effect the taste of the beer (I suppose the aluminum anode would effect taste less), or are the concentrations of the ions so low that it doesnt matter?

The other crazy idea I had, though kind of expensive, is a powered anode such as: http://www.sdsmarket.com/9006247005_...node-short.htm

A little expensive I know, BUT then you have no metal ions running around and no galvanic reactions.

I'm trying to find the best solution for the price. I could build my own powered anode from scratch if I could get a schematic for one, but I cant seem to find one (much cheaper than buying one I bet).

I wouldnt mind using the POR-15 solution (it seems to be a nice one) but I dont want a permanent instalation, and just doing the face plate I'm worried about rusting the threads.

Oh, and here's the elements I'll be using: (the normal camco ones) http://www.ronshomeandhardware.com/5...t-p/808790.htm


Are there any better idea's/solutions per cost? or are my pressent concerns not valid?

thanks!


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Old 04-13-2010, 04:10 PM   #2
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I suggest using the aluminum anode. Fears about aluminum are unfounded; for some reading check out this link: http://www.homebrewtalk.com/f11/faq-...kettles-49449/

People using aluminum boil kettles have no rust issues with their elements because of the nature of the mild steel/aluminum. I personally use an ~2.5" x2.5" piece of aluminum flashing ($0.25 at the local hardware store) drilled to slide over the threads of my elements. Works perfectly-- zero rust.



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Old 04-13-2010, 05:57 PM   #3
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i understand about the aluminium kettles, but being that it's used as a sacrificial anode, doesn't that pretty much guarantee that it's ending up in the beer? does your aluminium corrode or need to be replaced?
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Old 04-13-2010, 05:59 PM   #4
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With an aluminum pot, given that you have a mild steel as the face plate of the element, the aluminum pot will act as the anode and will "pit" as the ions are replaced, but with a pot like that my guess would be that it would take 100 years for you to really wear your pot down (or longer), and given its very large surface area, the pits are likely so small that every time you scrub the pot they go away, so you'll never notice, and the pot will more likely ware out for other reasons before it does for being the anode. Typically in a hot water heater, 40 gallons, constantly heating 40 gallons of water a day, a typically 42 inch long 1 inch thick anode rod will last 6 years.

Given that it would take a long time to effect your pot, and the flashing suggested above will eventually ware out, by pitting, then breaking apart, and when it does, you simply replace it.


Aluminum flashing eh... that sounds like the right price and it has a larger surface area for good conduction to act as the anode.... After reading the FAQ it seems that there isnt enough aluminum ions infused into the wort over a 1 hour boil to cause any issues...

Given the cheapness of the flashing, and its ease of install, I think I'll just go with that, and then replace it after its been eaten away (after how many years of use? haha).

Wayne at bargain fittings sells aluminum 1 inch NPS hex nuts for the heater elements too, and they are only a few dollars more than the SS ones, but the flashing is so cheap and easy I think I'll just go with that.

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Old 04-13-2010, 06:44 PM   #5
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kezgin,

As shushikiary states, there will only be trace amounts of aluminum (less than what is found in a "Daily" vitamin)... I have had my flashing anode in use for ~6 months now without any physical change to the naked eye, and it spent almost two weeks completely submerged too. Under microscopic conditions I am sure there is something happening, but again, that is going to be statistically insignificant amounts for a 5 gallon batch boiling for 60-90 minutes.

But, def do what you feel comfortable with, but I also warn against being afraid of the bogeyman!

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Old 04-13-2010, 08:44 PM   #6
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I have been dealing with this same problem since I made my electric keggle HLT. I recently tried using and aluminum bolt to act as the anode, but I still have been getting rust. Does the sacrificial anode have to contact the element base? or since the rusting had already started ( I cleaned it really well between tests ) it's too late to stop? Or I just have a really crappy water heated element?

I was really excited about this project, but now not so much if I'm going to get rust every time I use my HLT.
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Old 04-13-2010, 08:53 PM   #7
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I think you guys are over-analyzing this.

Food grade silicone on the element face and threads (once installed) will prevent further rust and still allow removal in the future. Simple, safe, long-lasting, and inexpensive.
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Old 04-13-2010, 08:58 PM   #8
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The way cathodic protection works by way of sacraficial anode, you need to have a GOOD connection between the anode and the electrical path to the cathode. Meaning that you need a fairly good connection between your metal brew pot and the sacrificial anode, as well as it being IN the water.

The easiest way to make sure this works right is to have direct contact to the cathode as you just mentioned, but it's not required to work.

The other way is to use a metal that is MUCH more "sacrificial" like magnesium instead of aluminum. This is why the mag fire starters can just be dropped in, because they dont need as good of a connection to work as well (higher potential, therefore higher resistance is ok).

Here we can see the table of the potentials of each metal: http://en.wikipedia.org/wiki/Cathodic_protection

Notice the magnesium is over 2x the negative potential of the aluminum, it's a better sacrificial anode.

Of course there could be other problems with your setup that we dont know about. It is entirely possible that you left some rust behind in the pits of the face plate and that is what is coming back.

Perhaps it would be a good idea to remove your whole element, and soak it in a rust removing solution to make 100% sure you got all the rust off.


Lamar guy: I think that might also work as a solution and not make it permanent, but does it seal well enough, and how did you seal it, did you just plaster the whole element nut and parts in the water (maybe a picture of exactly what you did would be helpful)?

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Old 04-13-2010, 09:22 PM   #9
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That's is an excellent answer and feel better about getting this to work without a band aid fix. Just to show what I have here is a picture. I have the element installed with a stainless nut and o-ring and a aluminum bolt that I screwed into the pot. I thought this was enough contact but maybe it's not. Also I believe I have some residual rust left behind.



Thanks for the help!

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Old 04-13-2010, 09:30 PM   #10
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Quote:
Originally Posted by cyberbackpacker View Post
kezgin,

As shushikiary states, there will only be trace amounts of aluminum (less than what is found in a "Daily" vitamin)... I have had my flashing anode in use for ~6 months now without any physical change to the naked eye, and it spent almost two weeks completely submerged too. Under microscopic conditions I am sure there is something happening, but again, that is going to be statistically insignificant amounts for a 5 gallon batch boiling for 60-90 minutes.

But, def do what you feel comfortable with, but I also warn against being afraid of the bogeyman!

gotcha. i wasn't sure if there would be any negative impact on water chemistry or not, but if it's hardly decaying i can't imagine it's that bad


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