Jack,
Not sure how to explain this.
There will be no reaction between the magnesium & it's inner support core.
Sacrificial anode --
The steel tank & the magnesium anode along with an electrolyte form a
battery in which the magnesium is gradually consumed. For this to
work, there must be a COMPLETED CURRENT PATH/LOOP between the two metals.
One portion of the connection is the point where the tank & anode are
physically joined. For a current to flow, there must be a completed
circuit. It has to flow in a loop, electrically speaking.
The other half of the electrical circuit is the current flowing
between the steel tank & the anode through an electrolyte, in this
case water. No electrolyte, no current, no protection.
As originally intended, in the water heater, the anode is more or less
centrally located, totally immersed in electrolyte, & the entire inner
surface of the tank is protected.
If you lay the anode in the bottom of the tank & it is immersed in
water, a protective current would flow between the anode & tank
through the water. There would be no current flow between the portion
of the tank & anode that did not have the electrolyte (water) between
them.
So yes, the very bottom of the tank might be protected but not the
remaining 99%.
The key is a complete current flow path, tank - electrolyte - anode -
tank to anode connection.
Personally I would rather drain the tank & keep it dry instead of
intentionally leaving water in the tank in hopes that the anode might
provide a bit of protection.
Regards,
Dave
Jack Brooks wrote:
> Dave,
>
> No, I don't think so.
>
> If the anode is connected to the steel tank, the magnesium anode
> will react with the steel it is in contact with. I believe that
> the reaction will take place between the magnesium and the steel
> center rod it is formed around, instead of between the magnesium
> and the water. At least that's how it looks logically to me.
>
> Back to my initial logic.
>
> Putting the anode at the bottom of the tank, provides a long
> contact area, and any water at the bottom of the tank would provide
> that electrolyte.
>
> Now I am back to thinking. . . . . Which is better?
>
> Jack
>
> -----Original Message----- From: Dave & M
> [mailto:rusd@sitestar.net] Sent: Friday, August 10, 2007 11:48 AM
> To: Jack Brooks Cc: 'Shop-Talk List' Subject: Re: [Shop-talk] FW:
> Anode for compressor
>
> Jack,
>
> What are you going to use for electrolyte, fill the tank with
> water? Otherwise, it will be just like a battery with no
> electrolyte in it.
>
> Dave Russell
>
> Jack Brooks wrote:
>
>> Thanks for all of the responses.
>>
>> I do believe that having a solid connection to the tank has
>> merit. I had not thought about that. While I'm not going to
>> weld or bolt up to an certified tank, I'm looking at ways that I
>> can attach the anode to the 2 inch (+/-) plug in the tank. It
>> could then be screwed in.
>>
>> Yes, I am aware of how nicely Magnesium burns. We used to use it
>> in the manufacture of 75 and 90mm artillery sabots and I happen
>> to be near a milling machine when they ignited one. YIKES!
>>
>> Jack
_______________________________________________
Shop-talk mailing list
http://autox.team.net/mailman/listinfo/shop-talk
|