Originally Posted by
SpeedRanger
For about six months I've been washing my bikes using water generated from a pellet salt softener. I was wondering if this will harm the bikes in the long term as the frames and wheels are aluminum with a mix of carbon or aluminum stems and seat post. Groupsets are all mid range Shimano.
Should I switch over to using city supplied water or stick with the salt water?
Technically, hard water is “salt water”. It just doesn’t happen to be sodium chloride water. A “salt” is any inorganic chemical that results from the combination of negatively charged ion and a positively charged ion. In chemical nomenclature, the positively charged ion is first in the name while the negatively charged ion is the second part. “Sodium chloride”, for example has positively charged sodium ions and negatively charged chloride ions in equal proportion. In solid form they are in a crystal lattice and in solution they are loosely combined with each other in the liquid matrix. In hard water, the common “salt” is calcium carbonate or magnesium carbonate...often both.
Magnesium and calcium are the problem. They interfere with detergents often causing the surfactant to crash out of solution which makes it ineffective as a cleaner. Ion exchange resins “exchange” two sodium for each magnesium or calcium in the carbonate resulting in a sodium carbonate. Sodium carbonate is “softer” because it doesn’t interfere with the surfactant. There isn’t any chloride present because the only thing exchanged was the sodium.
Chloride is what does the damage to metal parts. It can react with iron and aluminum to make both iron and aluminum chloride. Both of those are less stable then the oxide of aluminum and iron which results in exchange of the chloride for oxygen and release of the chloride. The chloride is free to go back and pluck out more of the metal.
Bottom line: It’s okay to wash your bike with softened water.
If you want even more nerdy information, we humans can’t drink water with a lot of sodium chloride in it because it draws water out of our tissues and causes dehydration. (Cats can drink salt water because their kidneys filter out the salt.) We can tolerate a higher load of other kinds of salts like carbonates.