No, Reverse Osmosis (RO) and demineralization are not the same at all.
RO water is water forced through a semi-permiable membrane with pores
small enough that most ions don't come through. It is NOT
demineralized, and will contain some dissolved salts. How much depends
on age of membrane, pressure, and initial water supply.
Demineralized water has had ALL the salts, both anions and cations,
removed by ion exchange resins that remove the salt ions and replace
them with either a hydrogen (H+) or hydroxyl (OH-) ion. pH of the
final water will partially depend on the initial mineral content, but
will fall to around pH 4 from the formation of carbonic acid from
dissovled CO2 from the air.
Either can be used to mix antifreeze, but since they are mineral
depleted, they will be more corrosive that low mineral tap water if the
antifreeze doesn't contain sufficient buffering capacity.
Standard green antifreeze uses polyphosphate corrosion inhibitors, and
will form insoluble aluminum phosphate sludge when they become
exhausted -- this is what plugs aluminum rads. It cannot be removed by
anything you want to pour into your cooling system.
Peter
