A corrosion inhibitor for use with Urea Ammonium Nitrate solutions is disclosed, comprising a blend of molybdate and one or more of the inorganic phosphates (including phosphates, polyphosphates, and pyrophosphates) and organic phosphates or phosphonates. Inorganic phosphates include, but are not limited to, SHMP (Sodium Hexametaphosphate) and TKPP (Tetra-Potassium Pyrophosphate). There are numerous other inorganic phosphates that will also serve as suitable secondary inhibitors. Organic phosphates or phosphonates include, but are not limited to, HEDP (1-Hydroxyethylidine-1,1-diphosphonic acid; also known as ethanol diphosphonate, acetodiphosphonic acid, or etidronic acid), ATMP or AMP (aminotri(methylenephosphonic acid)), PBTC (Phosphonobutane tricarboxylic acid), DETPMP (Diethylenetriaminepenta(methylene phosphonic acid)), and HPA (hydroxyphosphono acetic acid). There are numerous other organic phosphates and phosphonates that will also serve as suitable secondary inhibitors. The amount of molybdate can range from 1 ppm to 500 ppm by weight of fertilizer solution, with the preferred range from 10 ppm to 200 ppm. Amounts of inorganic or organic phosphate can also range from levels as low as 1 ppm up to 500 ppm, with the preferred range being from 5 ppm to 50 ppm.