[TheForge] Diesel fuel tank qry (Was: Re: fire steels)

[paul]

Peter Fels & Phoebe Palmer wrote:
> Jerrry: I'm confused, again.
> I'd assumed that a dielectric element in a mixed metal assembly would be 
> non-conducting, like plastic, ceramic,mica and so on...that wouldn't 
> pass on current.
> If you use copper, wouldn't that accelerate the corrosion on the iron?
> What do i have wrong here?...pete f
> 
> Jerry Frost wrote:
>> Uh. Yes, bronze dielectrics. Are they made from something else? Look 
>> like bronze but you know how copper alloys can fool ya. There's one in 
>> every connection between copper and iron in the house plumbing too.
>>
>> Frosty

We used to use dielectric unions between dissimilar metal to prevent 
electrolytic (galvanic) corrosion. After a while the almighty 
mucky-mucks in the code world determined that dielectric unions did not 
really help as the problem occurred through the electrolyte (water with 
dissolved minerals) between the metals. We are now directed to use 
transition adapters, ie copper to brass to iron, in an effort to reduce 
electrolytic corrosion. Don't know how successful that is, best not to 
mix metals, or in the case of a water heater with an iron tank and 
copper piping, add an anode rod of aluminum or magnesium, a sacrificial 
anode.
Normally the mixing of copper and iron (galvanized iron) piping results 
in the earlier death of the iron pipe. An exception to this is rust 
particles carried out of a dying water heater left to lie on the bottom 
of a copper pipe. This seems to cause pitting of the copper to the point 
of 'rust' through... this from the
Copper Institute on 'Ask This Old House' some time ago. The only holes 
were in the bottom of the pipe, electrolytic corrosion seems to occur 
wherever it damn well pleases.

-- 
Paul Sperbeck
WB9HCO
jadap

  "The difference between genius and stupidity is that
genius has its limits." -Albert Einstein
"Life is hard...it's harder if you're stupid" John Wayne - Sands of Iwo Jima