1-Hydroxyethanediphosphonic acid sodium salt is an organophosphonic acid scale and corrosion inhibitor that can form stable complexes with various metal ions such as iron, copper, and zinc, and can dissolve oxides on metal surfaces. It maintains good scale and corrosion inhibition at 250℃, remains stable at high pH, is not easily hydrolyzed, and is generally not easily decomposed under light and heat conditions. Its acid and alkali resistance and chlorine oxidation resistance are better than other organophosphonic acids (salts). It can form hexagonal ring chelates with metal ions in water, especially calcium ions, thus exhibiting good scale inhibition and a significant solubility limit effect. When used in combination with other water treatment agents, it shows an ideal synergistic effect. HEDP-Na is most suitable for scale inhibitors and detergents in acidic formulations. It is hydroxyethylidene diphosphonic acid.