Red means Iron.  Yellow means sulfur.  Blue-Green means copper.  Regarding the way water works with metals.  (Not a chemist...Ha-ha!)

But like Dennis said, magnets won't hurt.  Oh.....Gasoline tanks are made of steel; somehow water vapor gets inside of them, just a little bit at a time.  And then it goes downhill.  Gathering together the rust flakes (and they can be much bigger than dust) and holding onto those awful critters.  Also...it is my conjecture that the rust will happen slowly inside tank....and then just blurp.  And then they sink down.  And then they await for a low fuel tank fillup....and then they just naturally go for the easiest exit, taking with them whatever dirt or debris has somehow gotten into the tank.
Still thinking strong magnets to hold them (rust particles) in position are a reasonable idea.  Not perfect.  Way better than nothing.  And cheap.

    On Friday, September 6, 2019, 5:37:41 PM PDT, Richard Koerner <rjkinpb@sbcglobal.net> wrote:  
 
  Yep, it sure is; that red rust and all; it's Iron, just like those magnificent hills in the Southwest USA.  

OK...need somebody to go out to get some red dirt....with a magnet....and see if anything collects.  I'm sure it will happen.

    On Friday, September 6, 2019, 5:22:03 PM PDT, David Beierl <dbeierl@GMAIL.COM> wrote:  
 
 >
> So, instead of all these rust particles naturally flowing to the outlet,
> they are stuck at the 12 points.  Could buy a lot of time, decades even.

I don't believe ordinary red rust is magnetic...

Yrs,
d

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