"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 4.170...
"Jim Wilkins" fired this volley in
news:mn7cqm$2di
:

Here is the relevant corrosion mechanism those articles omitted:
https://en.wikipedia.org/wiki/Concentration_cell
"Concentration cell corrosion occurs when two or more areas of a
metal
surface are in contact with different concentrations of the same
solution."


Jim,
First, the phenonemnon you're referring to almost never happens in a
'mixing' environment. Second, the degree of 'concentration' must be
significant -- not horribly high, but higher than what you'd get
from
differences in the stream in a well.

Third... nah... not in a well. You don't see those sorts of things
going
on in a water well intended for human consumption.

This case is pure-and-simple mechanical abrasion from particulates.
I'll
bet there's a 4' deep 'sand pack' in that lift pipe before it turns
on,
which gets veritably BLASTED against the side of the pipe for a
second or
two every time the them pump comes on.

Lloyd

http://inspectapedia.com/water/Well_Casing_Leaks.php
Did you notice this:
"On the other hand, as corrosion in a well casing may be local to the
usual top of the static head in the well, the repair sleeve approach
may make sense."
That's the outer casing where water meets air, not within the delivery
pipe.

-jsw