Citric acid is an excellent chelating agent, binding metals by making them soluble. It is used to remove and discourage the build-up of limescale from boilers and evaporators. It can be used to treat water, which makes it useful in improving the effectiveness of soaps and laundry detergents. By chelating the metals in hard water, it lets these cleaners produce foam and work better without need for water softening. A solution with a six percent concentration of citric acid will remove hard water stains from glass without scrubbing. In industry, it is used to dissolve rust from steel and passivate stainless steels. Citric Acid is also used as a pH-control medium in slurry- & water-treatment facilities.