Abstract: 1,2-Ethane diphosphonates of the general formulaM.sub.2 O.sub.3 P--CH.sub.2 CH.sub.2 --PO.sub.3 M.sub.2wherein M is hydrogen, metal ion, ammonium, alkyl ammonium or mixtures thereof, are disclosed as inhibiting the corrosion of metals by oxygen-bearing waters. The 1,2-ethane diphosphonates can be employed either alone or in combination with certain thiols, 1,2,3-triazoles, zinc salts, chromates, silicates, inorganic phosphates, molybdates, tannins, lignins, lignin sulfonates, certain calcium and magnesium salts and mixtures thereof.

Abstract: Carboxylated lactones of the general formula ##EQU1## wherein R.sup.1 and R.sup.2 are individually selected from hydrogen, hydroxy, alkyl, hydroxyalkyl, --COOM, --CHOHCOOM, --CH.sub.2 COOM and a 1,3-dioxolane, 5-oxo group, and R.sup.3 is selected from hydrogen and --COOM, wherein M is hydrogen, alkali metal, ammonium or alkylammonium, provided that at least one of R.sup.1, R.sup.2 and R.sup.3 contain a carboxyl group, are disclosed as inhibiting the corrosion of metals by oxygen-bearing waters. The carboxylated lactones can be employed either alone or in combination with thiols, 1,2,3-triazoles, zinc salts, chromates, silicates, inorganic phosphates, molybdates, tannins, lignins, lignin sulfonates, calcium and magnesium salts and mixtures thereof.