Reply to "Rusty Brown Coolant"

Interesting, RR. The color change you observe is good. Iron oxide comes in two varieties: Fe2o3 is fully oxidized ferric iron, brown in color. FeO2 is partly-oxidized ferrous iron, black in color, so that treatment removed some oxygen from the iron (as well as some iron, too). Unless your coolant stays on the 'base' side with a pH of 7.0 or higher as measured by swimming pool test strips, the iron will slowly revert to the more stable form of red/brown. Keeping coolant on the basic side also slows corrosion of any aluminum in the system: radiators, water pumps and cylinder heads. Good info.