Washing a car with hard water is a pain, because you get water spots.
However, softened water has sodium in it, and I have always heard that salt (sodium chloride / potassium chloride) is bad for cars, because it produces corrosion.
Is the sodium present in softened water also harmful to cars, or do chloride ions need to be present as well for that to be the case?
I swear replied to a similar thread not to long ago but I couldn’t find it.
Yes sodium is bad for cars.
The amount of actual sodium added to the water is so insignificant I doubt anyone could produce a study showing washing a car with softened water is any more harmful then unsoftened water.
I’ve always used softened water when washing my cars. Conveniently one of the places I’ve worked for for the past 16 years is a water treatment company. The water there is softened and is a nice strong 90 psi.
my understanding on corrosion is that common salt ( sodium chloride) is bad mainly due to the chloride which complexes with the iron rather than the sodium. There may be a general effect due to the enhanced conductivity of the water in some cases due to teh sodium though in galvanic corrosion.
Many corrosion inhibitors are sodium salts! e.g. sodium silicate and sodium phosphate - which protect by a combination of pH control and forming a protective layer.
from http://www.harriswater.com/corrosion.htm
"The simple replacement of hard water calcium and magnesium with soft water sodium or potassium has no detrimental effect on water contacting materials. In fact, the non-scaling characteristic of soft water is a benefit to such pumping and plumbing appurtenances. Ion exchange water softening neither causes nor controls corrosion. "
Great, thanks for the info guys.