The alloying of zirconium to improve corrosion resistance has an empirical basis, and satisfactory explanations for the alloying effects are not available. A theory of compensating valencies in the corrosion oxide is proposed, in which cations of lower and higher valence than zirconium (+4) are present in ratios such that electrostatic neutrality is ensured. An example is an alloy containing equimolar amounts of scandium (+3) and niobium (+5). A number of zirconium alloys were prepared in which scandium or yttrium were paired with elements capable of a +5 or +6 valence. The ternary alloys containing scanadium were superior to the alloys combining yttrium. The alloys containing scandium plus molybdenum, tantalum, or tungsten had relatively long lifetimes in steam at 540 deg C and 600 psi as compared with other alloy combinations, including Zircaloy-2. A quenched alloy containing 0.025 wt% Sc and 0.053 at.% Mlo, that is, 0.05 mol.% of each additive, corroded approximately according to a cubic law up to 758 hr, at which potnt the rate suddenly increased in a manner suggesting hydrogen damage. Examination of the oxide film from alloys containing scandium and molybdenum showed only monoclinic ZrO/sub 2/. It is believed that stabilization of this form of ZrO/sub 2/ instead of the cubic or tetragonal forms is a factor in promoting corrosion resistance. In this way the protective character of the film can be improved independently of the addition of cathodes. (auth).