Abstract: This invention relates to a corrosion inhibitor for protecting metallic surfaces which are in contact with water, in particular circuits, apparatus and devices which use water as energetic or thermic fluid, said corrosion inhibitor being a fluorophosphate compound selected from the group consisting of:(i) compound of the formula M.sub.2.sup.I PO.sub.3 F, xH.sub.2 O(ii) compound of the formula LiM.sup.I PO.sub.3 F, xH.sub.2 O(iii) compound of the formula NaM.sup.I PO.sub.3 F, xH.sub.2 O(iv) compound of the formula M.sup.II PO.sub.3 F, xH.sub.2 O(v) compound of the formula M.sub.2.sup.I M.sup.II (PO.sub.3 F).sub.2, xH.sub.2 O(vi) compound of the formula M.sup.I PO.sub.2 F.sub.2, xH.sub.2 O(vii) compound of the formula M.sup.II (PO.sub.2 F.sub.2).sub.2, x H.sub.2 O(wherein M.sup.I is Na, K, Rb, Cs or HN.sub.4 ; M.sup.II is Mg, Ca, Ba, Sr, Zn, Cd, Mn, Ni or Co; and x is an integer or a fractional number comprised between 0 and 6) and(viii) mixtures thereof.

Abstract: The present invention relates to an anti-corrosion composition, which contains:(a) at least a polyamine with a molecular weight greater than or equal to 320 and answering to the general formula:R--[NH--(CH.sub.2).sub.3 ].sub.n.sbsb.1 --NH.sub.2wherein R is a saturated or unsaturated aliphatic C.sub.12 -C.sub.22 hydrocarbon radical; and n.sub.1 is an integer varying between 1 and 7 inclusive, R and n.sub.1 being such that the molecular weight of the said polyamine is greater than or equal to 320; and(b) at least one alkylenephosphonic acid derivative selected from the group constituted by the aminoalkylenephosphonic acids derivatives and the alkylenepolyphosphonic acid derivatives.The invention further relates to the method for preparing the said composition.Said composition is useful to inhibit the corrosion of metallic surfaces caused by water, in liquid or steam form.