A chelating agent is the main component of some rust removal formulations.
Citric acid is used to soften water in soaps and laundry detergents. A common synthetic chelator is EDTA. Phosphonates are also well-known chelating agents. Chelators are used in water treatment programs and specifically in steam engineering.  Although the treatment is often referred to as "softening," chelation has little effect on the waters mineral content, other than to make it soluble and lower the waters pH level.